ORAL PRESENTATIONS

New Chemistry Among Metal-Rich Tellurides of the Rare Earth Metals

John D. CorbettDepartment of Chemistry, Iowa State University, Ames, IA (USA)

Explorationof the telluride chemistryof the combinedgroup3 transitionmetalsandthelanthanidesrevealsa rich varietyof newchemistry,especiallyfor Sc,Y, Dy, Lu.Thesmallelectron-poormetalSccombinedwith thelargeTe "spacer"affordssignificantmetal aggregationin new lower dimensionalisotypesof electron-richergroup 4 metalchalcogenides,viz., as Sc2Te, Sc8Te3, Sc9Te2, hexagonal Sc6MTe2 (M = Fe–Ni).Significantdifferencesbetweenthe relatedpairsof compoundswill bedescribed.OtherunusualresultsincludetheuniqueSc5Ni2Te2, Y5M2Te2 (M = Fe–Ni),which exhibit novel"cut-and-paste"relationshipswith Gd3MnI3-type,the condensationreactionsthat convertSc2Te to orthorhombicSc6MTe, M = Pd,Cu, Ag, Cd,andtheuniqueSc14M3Te8, M = Ru,Os. Relatedexplorationsof tellurides of the heavy lanthanides,Gd, Dy, and Luespecially,will alsobe outlined,particularlyfor R2Te, otherR6MTe2, R11Te4, andLuxTe(x = 7, 8). Theresultsdemonstratesomeimportantrelationshipsbetweenthis 5d orbitalchemistry and that of the 3d and 4d transition metal elements. Important factors in EHTBband results, orbital and bonding properties, and matrix effects will also be presented.

Dimensionally Limited Transition Metal Pnictides: Synthesis and Characterization.

Stephanie L. BrockDepartment of Chemistry, Wayne State University, Detroit, MI 48202

Thedimensionalityof materialsplaysa largerole in materialphysicalproperties,andwhenlimited, canresultin drasticallyalteredbehavior. Dimensionallimiting canbeimposedby control of particlegrowth, aswhenextendedsolidsaremadeas nanometersizedparticles,or canarisespontaneouslyasa structuralmotif in anextendedsolid,suchasthepresenceof 1-D chainsor 2-D planeswithin a crystal. Themainobjectivesof theBrock group are to preparenew low-dimensionalmaterialsusing a combination ofsolution and solid-statetechniques,and develop a fundamentalunderstandingof therelationshipbetweenstructure,dimensionallimiting, andphysicalproperties(magnetic,electronic,optical) in thesematerials. In this presentation,two examplesof our effortstopreparedimensionallylimited transitionmetalpnictideswill bediscussed.First, a newlydevelopedroutefor thesynthesisof binarypnictidenanoparticlesof iron andmanganesebasedon reactionsbetweenmetal carbonylsand phosphines/arsineswill be introducedandthemagneticpropertiesof theresultantmaterialsdiscribed. Second,a seriesof solidstatematerialsfeaturing 1-D mixed pnicogen(P, As) chainsin the solid state(Cu2P3-

xAsxI2; x<0.5) will be describedalongwith the influenceof arsenicincorporationon thestructure,stability, and optical properties. Finally, the specific role of dimensionallimiting in thedevelopmentof propertiesin thesetwo different classesof materialswillbe discussed.

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Dimensional Reduction in Niobium Oxychloride Cluster Compounds: Synthesis andCrystal structure of Cs2InNb6Cl15O and its relationship with AxNb6Cl12O2

Yan Zhihua and A. LachgarDepartment of Chemistry, Wake Forest University, Winston-Salem, NC 27109

Low-dimensional materials containing transition metals attract significantattentiondue to their remarkablestructuraland physicalpropertiesand wide rangeofapplications.Our investigationof the useof a combinationof oxygenand chlorine asligandsin octahedralNb6 clustersto preparelow-dimensionalcluster-basedmaterialsledto the discoveryof a numberof novelphaseswith surprisinglydiversetopologies.1-4 Thepresentationwill describethe synthesis,singlecrystalx-ray diffraction studiesof a newmember of this family, InxNb6Cl15O, which has a 2D framework. Crystals ofCs2InNb6Cl15O were initially found as minor by-productin a reactionaimedto prepareCsxInyNb6Cl12O2 from amixtureof NbCl5, Nb2O5, Nb, In, andCsClin a sealedquartztubeat 720°C. Cs2InNb6Cl15O crystallizesin themonoclinicsystem(spacegroup:P 21/c) witha = 15.9699(3), b = 11.7073(2), c = 13.0993(2) Å, β = 100.58(1)°,V = 2407.4(8)Å3, andZ = 4. Its 2D framework is based on octahedral niobium oxychloride clusters(NbClO)ClO linked throughfour outerchlorineligands(Cla) to four different clusterstogeneratelayers// to the (ac) plane.Two adjacentlayersare linked throughtwo oxygen

ligands(Oi andOa) in the b directionto generatedoublelayerswith clusterconnectivity(NbClO)ClClO.TheIn andCscationsaredisorderedon 4 siteslocatedon thesurfaceofthe double-layers.The relationshipbetweenthe structureof Cs2InNb6Cl15O and that ofInxNb6Cl12O2, and the role played by the oxygen ligands will be discussed.

(NbClO)ClO AxNb6Cl12O2

(3D)(NbClO)Cl

OCs2InNb6Cl15O(2D)

Views of the cluster units and their linkages leading to the 3D framework in AxNb6Cl12O2 anda 2D framework in Cs2InNb6Cl15O.

References:1. E. V. Anokhina, T. Duraisamy, A. Lachgar, “Preparationof Low-dimensionalCluster

Materials:Synthesis,StructureandPropertiesof A2Ti2Nb6Cl14O5 (A = K, Rb,Cs),a SeriesofOne-dimensional Titanium Niobium Oxychlorides” Chem. Mater. 2002, 14, 4111-4117.

2. E. V. Anokhina,CynthiaS.Day,Hans-JürgenMeyer,MarkusStröbele,SusanM. Kauzlarich,HyungrakKim, Myung-HwanWhangbo, AbdessadekLachgar,“Preparation,Structure,andPropertiesof a Seriesof AnisotropicOxychlorideClusterCompoundsAxNb6Cl12O2 (A = K,Rb, Cs, or In)” Journal of Alloys and Compounds, 2002, 338, 218-228.

3. E.V. Anokhina, C. S. Day, A. Lachgar, “A New Quasi-One-DimensionalNiobiumOxychloride Cluster Compound Cs2Ti4Nb6Cl18O6. Structural Effects of LigandCombination,” Inorg. Chem., 2001, 40, 5072-5076.

4. E.V. Anokhina, C. S. Day, A. Lachgar, “A new layered niobium oxochloride clustercompound with novel framework topology”, Chem. Comm. 2000, 16 1491-1492.

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The New Supertetrahedral Clusters [M4Sn4S17]10- (M = Mn, Co, Zn)

Oleg Palchik, Ratnasabapathy G. Iyer, J. H. Liao, Mercouri G. KanatzidisDepartment of Chemistry and Center for Fundamental Materials Research

Michigan State University, East Lansing, Michigan, 48824

We used the alkali metal polysulfide technique and conventional directcombinationreactionsto synthesizea family of supertetrahedralmixed metal clusters.Unlike other known supertetrahedralclusters which can be consideredas excisedfragmentsform thediamondlattice,theoneswe describeherehavea differentstructuralmotif.

In this talk we presentextensionof our work for the preparationof the complexnew compoundsusing polychalcogenide-fluxmethod.Theseisostructuralcompoundswere synthesizedin K2S/S flux and they have generalstoichiometryof K10M4Sn4S17,where M=Mn, Fe, Co, Zn, Cd and Hg. All this group possessamestructural motif:[M 4Sn4S17]10- isolatedclusters,which is surroundedby K+ ions. They all possesssharpoptical absorptionin the UV-VIS-NIR region. The incorporationof the magneticions(e.g.Fe2+) in thestructuregivesrise to interestingmagneticproperties.Moreover,duetothemolecularnatureof the K10M4Sn4S17 theyaresolubleis differentsolvents(e.g.water,formamide). Last property makes this group of compoundsespecially attractive forapplications as precursors for the sophisticated mesoporous structures.

Use of Mn2(CO)10 Carbonyl Complexes as Precursorsfor the Synthesis of MnPn (Pn= P, As) Nanoparticles

Susanthri C. Perera†, Georgy Tsoi‡, Lowell Wenger‡, and Stephanie L. Brock†

Department of Chemistry†, Department of Physics‡, Wayne State University, Detroit, MI48202.

Over thepastfew years,interestin fine magneticparticleshasgrownenormouslybecauseof their unusualmagneticbehaviorcomparedto conventionalbulk materials. Anumber of previous studies have reported the suppression of long-range magnetic order innanocrystallinematerialsdue to the presenceof single magneticdomain structures.Therefore,nanoparticulateferromagnetsdemonstratesizedependentcoercivefields. Sofar, studieshave beenmainly focusedon nanoparticlesof transition metals(Co, Fe),alloys(Fe-Pt),andtransitionmetaloxides(ferrites,etc.). TM (transitionmetal)pnictides(pnicogen= group15 elements;P, As) area classof compoundsthatshowa broadrangeof electronic and magneticpropertiesincluding ferromagnetism,magnetoopticalandmagnetoelasticproperties. Therefore,nanoparticulateTM pnictides are expectedtoexhibit novel,perhapsevensuperior,magneticandoptical propertiesin relationto theirbulk analogs. Accordingly our group hasbegunto explore the suitability of differentmethodologies for the production of TM pnictide nanoparticles.

We initiated our investigationusing desilylation strategies,which are formallynon-redoxandwell establishedfor main groupmaterials. This methodis successfulforpreparationof FePnanoparticlesbut to date,we havenot beenableto makeMnP by thisapproach.Recently,we wereableto producenanoparticlesof MnP by redoxchemistrybetweenzero-valentmanganesecarbonylcomplexesand a variety of phosphines.Theapplicationof this new route to the synthesisof other transitionmetalpnictide phases,especially MnAs and CoP, along with optimized synthetic parameters,structuralcharacterization, and magnetic properties of the resulting materials, will be discussed.

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Magnetic Ordering in Gd2Cl3 — An Example of Burdett’s Coloring Problem

Timothy Hughbanks and Lindsay E. RoyDepartment of Chemistry, Texas A&M University, College Station, TX 77842-3012

Spin densityfunctional(SDFT) calculationsof the d-f exchangecouplingfor thepseudo 1-D chain compound Gd2Cl3 has been carried out using the 1-D model,Gd8Cl12(OPH3)4, by consideringsevenvariationsin theorderingof the4f7 moments.Thecalculationsindicate that this semiconductingsystemshould exhibit antiferromagneticorderingof the4f7 momentsin a patternconsistentwith publishedspinpolarizedneutrondiffraction data. An attemptto accountfor the calculatedmagneticenergiesof spinpatternsusing an Ising model was unsuccessful,indicating that the latter model isinappropriate.The qualitativefeaturescanbe interpretedusinga perturbativemolecularorbital (PMO) modelthat focusestheinfluenceof the4f7-d exchangeinteractionon thed-basedmolecularorbitals. Fundamentalto thed-electronmediatedexchangemechanismis theintra-atomic4f7-d exchangeinteraction. Theessenceof this interactionis presentintheGd atom[4f75d16s2], which is computationallyinvestigatedwithin SDFT.Theon-siteperturbation induced 4f7-d exchangeis equivalent to use of different Hückel “αparameters”for different 5d spins — what Burdett would have called a ‘coloringproblem’. In Gd2Cl3, the d-electronmediatedf-f exchangeinteractionwas interpretedusing basic perturbation theory. Computeddensity of statesand spin polarizationinformation was used to support the perturbation-theoretic analysis.

Synthesis and Characterization of Novel Quaternary Alkali Metal ThioarsenatesUsing the Molten Flux Method

Ratnasabapathy G. Iyer and Mercouri G. KanatzidisDepartment of Chemistry and Center for Fundamental Materials Research

Michigan State University, East Lansing, MI 48824

Our group has beeninvolved in a systematicinvestigationof the reactivity ofdifferent metalsin alkali polythioarsenatefluxes. Thesefluxes haveprovedto be everybit rich andpromisingasits phosphatecounterpartin deliveringa plethoraof structurallydiverse quaternarycompounds.These reactive fluxes play the role of a solvent inallowing diffusion of reactantsandalsoparticipatein the reaction.Themeltingpointsofthesefluxes are in the 250°C-650°C temperaturerange,enablingreactionsto be carriedout at low temperaturesof 300°C -500°C. The outcomeof a reactionin sucha flux is afunction of the basicityof the flux, giving the chemista certaindegreeof control. In apolythioarsenateflux, anionicbuilding blocksof the kind [AsxSy]n- areformeddependingon the kind of metal presentand the basicity of the flux. Using Sn, we haveisolatedcompoundsranging from a molecular structure (Cs2SnAs2S9) to a two-dimensionalstructure(Rb2SnAs2S6). In gives molecular Cs6InAs3S13 while Pb leads to RbPbAsS4.Going to the transitionmetals,we preparedK4MnAs2S8, Cs2CuAsS5 andA4CdAs2S9. Thecompoundsobtainedin thesefluxes are very different from the onesobtainedin thechalcophosphatefluxes. All the compoundshavebeenstructurally characterizedusingsinglecrystalX-ray diffraction. PhysicalcharacterizationsincludeUV-Vis spectroscopy,Infrared and Raman spectroscopy, and Differential Thermal Analysis.

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Synthesis, Structural and Physicochemical Characterization of MnP@InP, NewMagnet-Semiconductor Core-Shell Nanoparticles

Kanchana Somaskandan1, Georgy Tsoi2, Lowell Wenger2, Stephanie L. Brock11Department of Chemistry, 2 Department of Physics, Wayne State University, Detroit, MI

48202

Theaim of this researchis to developa syntheticstrategyfor III-V basedmagnet-semiconductorcore-shellnanoparticles,and study the effect of size limitation on thepropertiesin thesematerials.Thetargetedcore-shellnanoparticlesareheterostructuresinwhich a magneticcore is coatedby a semiconductorshell resultingin a ferromagnetic-semiconductorjunction within eachparticle. Thesewould mimic heterostructuredthinfilms, which havepotentialspin-dependentapplicationsin new magneto-electronicandmagneto-optical devices. So far, only II-VI and III-V based semiconductor-semiconductorcore-shell nanoparticlesystemshave been reported. Thesematerialsexhibit unusualoptical propertiesincluding tunablebandgapsand sharpluminescence.Here, the synthesisof MnP@InP semiconductor-magnetcore-shell nanoparticlesisreported. The synthesisinvolves preparationof the magnetictransition metal (Mn)phosphidecore nanoparticlesfollowed by precipitationof semiconductingInP on thesurface. The resultant particles are isolated by size selective precipitation andcharacterizedby UV/Visible spectroscopy,X-ray powder diffraction, high resolutiontransmissionelectronmicroscopy,and SQUID magnetometry.The effect of syntheticconditions on size, sample homogeneity,and resultant physical properties will bediscussed.

Electrochemical Synthesis of Micro- and Nanostructured Films for Use inPhotoelectrochemical Hydrogen Production

Kyoung-Shin ChoiDepartment of Chemistry, Purdue University, West Lafayette, IN 47907.

Developingmaterialsthatcanproduceaneconomicalandenvironmentallybenignsourceof energyis undoubtedlyoneof the world’s mostpressingtechnicalchallenges.Our currentresearcheffort is focusedon developinghigh performancemicro- andnano-structuredelectrodematerials for use in photoelectrochemicalhydrogen production.Whenphotoelectrodesarepreparedaspolycrystallinefilms, interfacialstructureshaveasubstantialimpact on the overall efficiency of the photoelectrodebecausethe size,crystallinity, morphology, and texture of the particles dramatically changecatalyticactivity, chargerecombinationrate,andchargetransportpropertiesof thephotoelectrode.However, most of the previous studieson photoelectrodematerialshave focusedonidentifying a few candidate materials and optimizing their composition withoutsystematicallyaddressinginterfacial issues. This was becausesynthetic methodsformerly available to producephotoelectrodematerials(e.g. spray pyrolysis, sol-gel,electron-beamevaporation,spin coating)possesslimited control over the morphologicalfeatures of the particulate films. To develop highly efficient, area-effectivephotoelectrodematerialsan innovativeinterfacial synthetictechnologywill haveto bedevelopedso that the structure-propertyrelationship necessaryto design the bestinterfacial structure can be elucidated.

We are currently developinga novel synthetic strategy that combinesa softsolution electrochemicalprocesswith a biomineralizationinspired concept. In thisapproachwe electrochemicallyorganizeorganic matriceson the electrodesurfaceto

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direct and regulatethe nucleationand growth processesof inorganic materials. Thismethodprovidesus with a high degreeof syntheticfreedomfor interfacialengineeringand makes it possible to tune interfacial structuresas well as compositionsof thephotoelectrodematerials. In this presentation,we will introduceprinciplesof our newsynthetic method and discuss in detail the effects of compositionsand interfacialstructures on the photoelectrochemical activities of the photoelectrode materials.

Yb8Ge3Sb5: a New Mixed Valent Zintl Phase Containing (Ge3)4- Anions

James R. Salvador † Daniel Bilc‡ S.D. Mahanti‡, and Mercouri G. Kanatzidis†

† Department of Chemistry and Center for Fundamental Material Research ‡ Department of Physics and Astronomy and Center for Fundamental Material Research

Michigan State University East Lansing MI 48824

The new Zintl phaseYb8Ge3Sb5 hasbeenproducedby direct combinationof theelements and crystallizes in the tetragonal space group I4/mmm with lattice parameters a = 15.8965(8)Å,c = 6.8206(5)Å. This rare-earthmetal rich phasecan be chargebalancedin the following manner(Yb2+)6 (Yb3+)2 (Ge3)4- (Sb2-) (Sb3-)4 and is thereforeamixedvalentcompound.Theuseof electropositiveelementswith theability to bemixedvalentfor the exploratorysynthesisof Zintl phasesis a relatively new concept,andhasthe potentialto greatlyexpandingthe structuraldiversity of Zintl ions. The compoundpresentedherehasseveraluniquestructuralfeaturesincluding a new Zintl ion (Ge3)4-

which polymerizesto form a 1-dimensionalchainof edgesharingtetrahedra.Magneticsusceptibility,electricaltransportandHall effectmeasurementsaswell asab-initio bandstructure calculationswill be presentedto support the notion that this compoundrepresents a mixed valent system.

High Temperature and Ambient Temperature NMR Investigation of MetalSelenophosphate Syntheses

Christian G. Canlas, Mercouri G. Kanatzidis, and David P. Weliky*Department of Chemistry, Michigan State University

Many different metal selenophosphatecompounds can be synthesized in hightemperature(400 – 600 C) melts and thesecompoundscontaina rich variety of metalselenophosphateanions.In orderto understandbetterthechemistrywhich occursin thesemelts,syntheseshavebeencarriedout in situ in theNMR spectrometerand31P NMR hasbeenappliedto identify andquantify reactants,intermediates,andproductsoverthe timecourseof the reaction.For example,in a melt containingAg:P:Sein a 2:1:3 mol ratio,there are two distinct 31P signalswhich can be tentatively assignedto the PSe43– andP2Se6

4– anions,andwhich correlatewith thefinal ambienttemperatureproducts,Ag7PSe6and Ag4P2Se6, respectively.The observedsignalsare relatively broad,which could bediagnosticof chemicalexchangein themelt or of solid precipitationin themelt. For thePSe43– signal, the solid state NMR techniqueof magic angle spinning narrows thelineshape,which suggeststhat this anionexistsin somesolid or at leastslowly-rotatingform at high temperature.In a parallel study, ambienttemperature31P NMR hasbeenappliedto themetalselenophosphateproductcompounds,anda correlationwasobservedbetweenthe 31P chemical shift and the presenceor absenceof a P–P bond in theselenophosphateanion.This correlationwill beusefulin anionidentificationin thehigh-temperaturemelts.In addition,31P spin-latticerelaxationtimesweremeasuredat ambient

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temperature and showed a surprisingly large range (20 – 3000 s) among the differentcompounds. Two of the compounds which demonstrate fast relaxation were also shownto have detectable ESR signals. Although these compounds are not paramagnetic per se,they appear to contain paramagnetic impurities whose chemical identity is currentlyunder investigation. Overall, NMR has been shown to be a promising technique forunderstanding the high temperature syntheses of metal selenophosphates.

Physics among light-weights: Superconductivity in MgB2

Paul C. CanfieldAmes Laboratory and Department of Physics and Astronomy, Iowa State Univeristy

Superconductivity in MgB2 was discovered a little over two years ago. During thepast 24 months our understanding of this simple binary compound has grown at a breakneck rate and MgB2 has proven to be of great interest to both the basic as well as theapplied research communities. In this talk I will try present an overview of why this isthe case.

High purity, polycrystalline MgB2 can be synthesized in a variety of formsranging from sintered pellet to wire segment to thin film by simply exposing high purityboron with the desired morphology to Mg vapor near 900 C. For pure MgB2 Tc in near40 K, there is a clear boron isotope shift in Tc, the low temperature resistivity is near 0.5micro-Ohm-cm, and the anisotropy of Hc2(T) ranges from 2 close to Tc to near 6 at lowtemperatures. Carbon doped MgB2 can be synthesized by exposing the binary, carbon-rich, compound B4C to Mg vapor near 1200 C. The transition temperature is reduced tonear 22 K, the normal state resistivity appears to increase substantially, and theanisotropy in Hc2(T) at the lowest measured temperatures is close to 2. Remarkably, evenwith all of the changes mentioned above, the carbon doped MgB2 still manifests a cleartwo-gap signature in the low temperature specific heat data, implying that the twosuperconducting gaps are quite robust.

TRANSITION METAL ZINTL PHASES: NIOBIUM ARSENIDES AND BEYOND

Franck Gascoin and Slavi C. SevovDepartment of Chemistry and Biochemistry, University of Notre Dame

Notre Dame, Indiana, 46556

Compared to the large number of Zintl phases, there are only a few transition metal Zintlphases. Despite the large variety of transition metals and the numerous feasiblecombinations with main-group elements, this field remains quite underdeveloped andunexplored. We have been interested in the solid-state chemistry of the system alkalimetal – niobium – arsenic and have undertaken extensive and systematic studies of thesesystems. This has led to the discovery of the first mixed-valence transition metal Zintlphases, namely, K38Nb7As24, Cs9Nb2As6, and K9Nb2As6. Furthermore, another

degree of complexity was reached when a supplementary p-block element was used.Compounds such as Cs7NbIn3As5, K8NbPbAs5, K6NbTlAs4, or the more complex

Cs24Nb2In12As18, are some of the first discoveries in these complex and promising

systems.

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Charge, orbital and spin ordering in transition-metal oxide perovskites.

Patrick M. Woodward,Department of Chemistry, The Ohio State University, Columbus, OH 43210.

Transition-metal oxides adopting the perovskite structure (or closely relatedstructure types) are well known for their interesting electronic properties (i.e. High TC

superconductivity, colossal magnetoresistance, etc.). I will discuss structure-bonding-property relationships and phase transition behavior of a variety of compounds takenfrom one of the following two families: oxygen-deficient double-cell perovskitesLnBaM2O5+x (Ln = Nd, Sm, Tb, Ho, Y; M = Fe, Co, Mn), and ordered double-edgeperovskites A2MnMO6 (A = Sr, Ca; M = Mo, Ru). Many of the compounds with a singletransition metal ion undergo a transition from a delocalized to a localized electronicconfiguration, upon cooling from room temperature. The localization of the conductionelectrons is shown to trigger phenomena such as charge and orbital ordering, magneticordering, macroscopic phase segregation, and charge disproportionation. Charge-ordering is not common when multiple transition metal ions are present, but oxidationstate degeneracies can be utilized to achieve strong interactions between the magnetismand electronic transport properties. Variable temperature synchrotron x-ray and neutronpowder diffraction measurements are used in combination with transport and magneticsusceptibility measurements to characterize the behavior of these compounds.

New Semiconducting Sn- and Sb-Chalcogenides

A. Assoud, H. KleinkeUniversity of Waterloo, Department of Chemistry, Waterloo, ON, Canada N2L 3G1

We are interested in finding new materials suitable for the thermoelectric energyconversion. Promising materials comprise heavy elements, small band gaps (< 0.6 eV)and low symmetry, yet highly degenerated bands in the vicinity of the Fermi level.Recently we turned our attention towards Sr seleno-stannates, a hitherto unexploredsystem. Related compounds, e.g. in the A/Sn/Se (with A = alkaline metal) or Eu/Sn/Sesystem, typically contain the Sn atoms in the oxidation state +4, and then large band gaps(> 1 eV) - unless mixed-valent Se is present, one example for latter being Eu4Sn2Se10.Smaller band gaps may be achieved by using mixed valent Sn atoms, for the unoccupiedSnIV-s states will not differ much in energy from the occupied SnII-s states. With thiscontribution, we present our first three new compounds in this area, which compriseeither mixed valent Sn or Se, or - in a quaternary compound - SnIV and SbIII.

Sr4Sn2Se10 occurs in the Eu4Sn2Se10 structure type. Characteristic motifs of thisstructure are [SnIV

4Se14]12- fragments and (Se3)2- chains. SrSn2Se4 crystallizes in a distortedvariant of the SrIn2Se4 structure type. In this structure, the SnII and SnIV atoms are bothtetrahedrally coordinated, but exhibit quite significantly different Sn-Se bond lengths.[SnIVSe4]4- and [SnIISe4]6- tetrahedra are connected via edges to form dimeric units[SnIISnIVSe6]6-, which are connected to the next units via corners to build zigzag chains.Sr3SnSb2Se8 adopts a new structure type. This type exhibits corner sharing tetrahedra[SnIV

2Se6]6- that form a chain along the a axis. Edge sharing Sb-centered pseudo octahedrabuild chains that are connected via corners. Electronic structure calculations reveal asmall band gap of 0.2 eV for SrSn2Se4, a large band gap of 1 eV for Sr4Sn2Se10 andmetallic properties for Sr3SnSb2Se8.

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N-based Inorganic Materials by Experiment and Theory

Richard DronskowskiInstitute of Inorganic Chemistry, Aachen University of Technology (RWTH), 52056

Aachen, Germany

Inorganic materials containing nitrogen atoms, such as main-group molecular andextended nitrides, transition-metal and rare-earth nitrides, main-group and transition-metal cyanamides/carbodiimides, as well as transition-metal oxynitrides, offer a beautifulplayground for combined experimental and theoretical research in solid-state chemistry.

Explosive sulfur nitride, being subject to a crystallographic phase transformationvery close to its deto-nation temperature, readily reacts to yield a copper-rich amorphoussolid, the structure of which is successfully modeled on the basis of infrared/EXAFS dataand density-functional (DFT) calculations. Similar total-energy calculations utilizingperiodic boundary conditions are needed to clarify questions of phase and structuralstability for the binary nitrides of the 3d metals, and DFT techniques must also be used topredict or understand phenomena of magnetic ordering and structural distortions,especially for the binary systems Fe/N and Ce/N. Possibly driven by the search forcarbon nitride, the list of main-group and transition-metal cyanamides/carbodiimides(pseudo-sulfides by electron count and anionic volume) is constantly growing. Theirstructural and electronic varieties, however, pose an enormous challenge for DFTcalculations when it comes to reliable energetics and magnetic moments. Althoughpromising in terms of a synthetic "tuning" of the anionic part, only a very small numberof metal oxynitrides has been synthesized so far, and erroneous phase entries — nowspotted quite easily by ab initio theory — have been overlooked for many years.Nonetheless, there is a good chance of making novel oxynitrides of the magneticallyactive as well as early transition metals by means of unconventional synthetic methods,i.e., thermolysis of organometallic precursors and thin-film sputtering, respectively.Theory plays a major role in the structural characterizations of these electronicallyinteresting materials.

Low Density Metal Organic Frameworks for Fuel Gas Storage

J.L.C. Rowsell, N. Rosi, and O.M. YaghiMaterials Design and Discovery Group, Department of Chemistry,

University of Michigan, Ann Arbor, MI 48109.

The reversible sorption of gas molecules in metal-organic frameworks (MOFs)has successfully been used to demonstrate their high porosity. This process is now beingrealized as a practical way to store chemical energy; namely, as low hydrocarbons suchas methane. Our group has demonstrated the ability to tailor the surface interactions andpore size metrics within one isotopic series of zinc carboxylates, simply byfunctionalizing the organic component. This synthetic control allows optimization of thesorption properties of the material, such as total guest uptake and reversibility of guestsorption. We are now searching for new MOF topologies comprised of lighter metals inorder to obtain greater gravimetric storage capacities. Under this protocol, several Group2 carboxylate frameworks have been synthesized and structurally characterized, eachexhibiting secondary building units defined by the typical coordination geometry of themetal.

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Beyond crystallography: the structure of complex and nanocrystallineMaterials

Simon BillingeDepartment of Physics and Astronomy, Michigan State University, East Lansing, MI

48824

Increasingly we want our advancedmaterials to have precise and directedfunctionality. There is a generalrelationshipbetweenthe structuralcomplexity of thematerial and the uniquenessof its function. The ultimate functional materials areenzymes;complexbiological proteinsthat catalyzespecific reactionsin a cell. Thesemoleculescontainmany thousandsof atomsthat fold into a unique structure. Otherexamplesare materialswith finely balancedcompetinginteractionsclose to a phasetransition that result in large, and often useful, material susceptibilities.Colossalmagnetoresistantmanganitesand high-temperaturesuperconductorsare key examples.One thing thesefuntional materialssharein common is the presenceof meaningfulstructureson the nanometerlengthscale. One of the great challengesfacing us is tocharacterizethesenanostructuesbothquantitativelyandreliably. I will discussx-ray andneutrontotal-scatteringapproacheswe are using to addressthis problem. By way ofexampleI will focus on correlatedelectron materialswhere a competition betweenelectronic,magneticandlattice degreesof freedomresultsin a rich varietyof propertiesandground-states.I will discusshow nanostructuresandnano-scaleinhomogeneitiesarekey to understanding the properties.

Polyanions in Solids

Wolfgang JeitschkoInstitut für Anorganische und Analytische Chemie Universität Münster Wilhelm-Klemm-

Strasse 8 48149 Münster, Germany

After a brief introductionon Zintl compoundsandtheconceptof thetwo-electronbond, the talk will focus on somerecentwork of our group with the emphasison thestructuralchemistryof polyphosphidesand polyantimonidesof binary and ternaryrareearth and transition metals. The concept of the two-electron bond serveswell forpolyphosphideswhere it allows to rationalize chemicalbonding and to predict somephysicalproperties,becausein thesecompoundsthe phosphorusatomsusually do notexceedthecoordinationnumberfour. In contrast,in polyantimonidestheantimonyatomshavea tendencyfor highercoordinationnumbersandfractionalbondshaveto becountedto rationalize their crystal structures.

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The fascinating world of the thiophosphates of transition elements and/orlanthanides

Stéphane JobicInstitut des Matériaux Jean Rouxel, BP 32229, 44322 Nantes cedex 3, France

The low dimensionalmaterialsAxMQy (A= alkali metal, M= transition metal,lanthanideand/or main group element,Q= S, Se) exhibit structuralarrangementsthatdependstronglyupontheA/M ratio andthenatureof thecountercation.To someextent,such compoundscan be viewed as strongly covalently bonded,negatively chargeddomainselectrostaticallyshieldedfrom eachotherby alkali metalcountercations.Owingto existence of covalent and ionic chemical link, this type of materials can often beconsidered as ionic Ax+[MQy]x- salts. Hence, exfoliation and dissolution processes in polarorganic solvents can be envisioned. Recently, studies in solution have been carried out onKNiPS4 and KPdPS4 inorganic compounds. Both exfoliate in DMF and DMSO but twotypes of behavior in solution are displayed. While 1/∞[PdPS4]- chains are maintained insolution leading to a complex fluid behavior, 1/∞[NiPS4]- chains undergo a solvent inducedfragmentation with a reorganization into crown shaped discrete [Ni3P3S12]3- oligomerswhich can be stabilized in the solid state by metathesis. The reconstruction of the infinite1/∞[NiPS4]- from these discrete entities can also be done by playing with the nature of theorganic countercation and the followed chemical route.

Moreover, beside this exceptionalchemical reactivity of the KMPS4 phases,thiophosphatesof cerium have recently receivedmuch attention in the questof newcoloredinorganicmaterialsfor pigmentapplications.Indeed,theCe3+ cationappearsasadesirableelementin generatingcolor becauseof its ability to presenta parity andspinallowed Ce-4f1 → Ce-5d1 electronic transition. The position in energyof the relatedabsorptionthresholdcan be shifted in energyby playing with the ionicity of the Ce-Sbonding.Thecontrolof theopticalgapcanpracticallybeachievedvia aninductiveeffecton the Ce-Sbond from a third M element.The more covalentthe M-S bond,the moreionic the Ce-Sbond and the wider the Ce-4f/Ce-5dgap, and vice versa.Recently,theexplorationof the K/Ce/P/Q(Q = S, Se)systemsled to the stabilizationof new phaseswhich can be considered as a new member of the (K I

4(P2)VIIIQ-

II6)l(KI

3PVQ-II4)m(LnIII

4(P2)VIII3S-II

18)n(LnIIIPVQ-II4)o family (Ln= La, Ce; Q= S, Se).

Vacancy-doped Nd1-xTiO3. Magnetic and transport properties at the metal-insulatortransitions.

Athena Safa-SefatMcMaster University, Hamilton L8S 4M1, CANADA

The parent NdTiO3 compoundis a Mott antiferromagneticinsulator with anorthorhombicPerovskitestructure.By introducingcation vacancies(x) on the Nd-site,Nd1-xTiO3 undergoestwo metalto insulatingtransitions(MITs). The focusof this paperis the a detailedinvestigationof the polycrystalline sample compositions,in the vicinityof thetwo MITs, throughelectricalresistivity,magneticsusceptibility,SeebeckandHall-effect measurements.For the polycrystalline samples,Nd1-xTiO3 undergoesMITs atvacancycompositionsof x= 0.20andx ~ 0.08.DisorderandAndersonlocalizationplay asignificantrole in theMIT at x= 0.20.Thecompositionrange0.08< x < 0.20aremetals.A Kondo-likeelectronicgroundstatebridgesthe insulatorandcorrelatedmetalsnearx=0.08. Compoundswith x< 0.08 order antiferromagneticallyand are semiconductors.

11

Moreover, crystal-growth by the ‘modified Bridgeman method’ at different keycompositionsof the solid-solution is done; the single crystalsare comparedwith thesintered polycrystalline sample results.

Discovering New Oxides

Kenneth R. PoeppelmeierDepartment of Chemistry, Northwestern University, Evanston, Illinois 60208-3113

Solid state chemistry relies heavily on exploratory synthesis,and it is wellrecognized that the complexity of the possibilities open defies predictability.1

La4Cu3MoO12 exemplifies unpredictability.2,3 Despite the fact that the perovskitestructurewould seemfavorablebasedon cationsize, the rare-earthhexagonalYMnO3-typestructureforms. Theformationof manyoxideswith unpredictablestructurescanbeattributed to a balance between stable and unstable compositions. A surprising number ofthe membersof the Ln4Cu3MoO12 and Ln’ 2Ln”2-Cu3MoO12 (Ln = La – Nd, Sm – Lu)families form, all crystallizingin a hexagonalstructuresimilar to thatof YMnO3. Somedo not form becauseeither the averagelanthanidesize is too small or the differencebetweenthe sizeof Ln’ and Ln” is too large. Furthermore,evenif Ln’ 4Cu3MoO12 andLn”4Cu3MoO12 form single phases,attemptsto synthesizethe correspondingsolutionphase,Ln’ 2Ln” 2Cu3MoO12, may result in a mixture of simpler metal oxides! Theexplanationilluminates the importanceof unstable“umbrella” stoichiometriesfor theformation of unconventional structures in multication systems.4 References1. Uma, S.; Corbett, J. D. Inorg. Chem. 1999, 38, 3831-3835.2. Vander Griend, D. A.; Boudin, S.; Poeppelmeier, K. R.; Azuma, M.; Toganoh,H. Takano, M. J. Am. Chem. Soc. 1998, 120, 11518-11519.3. Vander Griend, D. A.; Boudin, S.; Caignaert, V.; Poeppelmeier, K. R.; Wang, Y.;Dravid, V. P.; Azuma, M.; Takano, M.; Hu, Z.; Jorgensen, J. J. Am. Chem. Soc. 1999,121, 4787-4792.4. Vander Griend, D. A.; Malo, S.; Wang, T. K. and Poeppelmeier, K. R. J. Am. Chem.Soc., 1999, 122, 7308-7311 (2000).

HYDROTHERMAL SYNTHESIS OF THREE DIMENSIONAL STRUCTURESUSING METAL OXIDE-FLUORIDES AND NEUTRAL BIDENTATE LIGANDS.

Paulette R Guillory, Heather K Izumi, Duward F Shriver, Kenneth R. Poeppelmeier*Northwestern University, Department of Chemistry, Evanston, IL 60208-3113

Non-centrosymmetric materials are of interest because their symmetry-dependantproperties, such as piezoelectricity, ferroelectricity, and second order non-linear optical(NLO) behavior, are the basis of numerous technological applications. LiNbO3, a wellknown inorganic NLO material, exhibits an out-of-center distortion in the individual[NbO6/2]- octahedra postulated to cause the non-linear response. These out-of-centerdistortions are replicated by metal oxide fluoride anions (MOF5

-2), where the polardistortion in the octahedra is inherent in the molecule itself, and not a product of a phasetransition. Compounds constructed with these metal oxide fluoride anions havehistorically crystallized without internal disorder, or crystallized with order but with an

12

anti-parallel arrangement of the anions, forming a centrosymmetric compound.Understanding the mechanism of crystal formation may enable the synthesis of a non-centrosymmetric compound where the octahedral anions crystallize without disorder, andwithout anti-parallel arrangement.

Metal oxide fluoride anions, particularly TaOF5-2, NbOF5

-2, MoO4F2-2 and WO4F2

-2

are easily synthesized using hydrothermal synthesis. The metal oxides are reacted with ahydrofluoric acid solution inside of Teflon pouches in a stainless steel, constant-volume reactor. The reactions are monitored and studied using a composition spacediagram, similar to a ternary phase diagram, where the products are related to the initialmole fractions of the reactants. The molar ratio of each reactant is recorded, with theother variables (temperature and amount of solvent) held constant.

One method to control the internal ordering of the metal oxide fluoride (i.e.[NbOF5] 2-] is through the use of a neutral bidentate ligand to coordinate to the cation (i.e.Cd2+) in a cis fashion. This cis coordinate cationic complex will bond to the oxide on theniobium, creating an ordered structure. If the anions are also in parallel arrangement, thestructure will be non-centrosymmetric. This area is being explored using early transitionmetal (Nb, Ta, Mo, W) oxide fluorides, late transition metal (Ni, Cu, Ag, Zn, Cd) cations,and neutral ligands (2,2’-dipyridyl amine).

A polymorph of CuNb(Pyridine)4OF5 using the anionic NbOF5-2, and cationic Cd+2

was synthesized. The basic chain of the two polymorphs is identical, but differ inpacking, and also the ordering of the oxide and fluoride ligands in the octahedral [NbOF5]2- unit. Further study of this polymorphism will lead to an understanding of syntheticmethods and allow a rational synthetic method to be devised to construct these materials.

Combinatorial Techniques for the Discovery & Optimization of Solid StateMaterials

Konstantinos ChondroudisSymyx Technologies, Inc., Santa Clara, CA 95051

Combinatorial synthesis and screening of extraordinarily large numbers ofdifferent organic compounds has been widely applied in the pharmaceutical industry fordrug discovery. At Symyx, combinatorial high throughput synthesis and screeningtechniques have been implemented to create integrated workflows that enable scientiststo discover and optimize materials across a broad range of applications at an acceleratedrate compared to traditional techniques. Solid-state materials are a crucial component ofmany new devices for technologically important areas. In this talk we will discuss howcombinatorial techniques were used to discover and optimize such solid-state materialsfor various applications.

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3-Dimensionally Ordered Macroporous (3-DOM) Solids as NanostructuredLi-ion Battery Materials

Scott J. Barry, Erin M. Sorensen and Kenneth R. PoeppelmeierDepartment of Chemistry, Northwestern University

Recently, three-dimensionally ordered macroporous (3DOM) solids (≥50 nm porediameter) fabricated by colloidal crystal template directed synthesis have attractedinterest owing to their unique photonic, catalytic, electrochemical and biosensingproperties. For example, electrochemical analysis of a 3DOM nickel sample indicatedthat the entire powder surface is electrochemically active and uniformly accessible [Stein,et. al. Adv. Mater., 1999, 11, 1003] . Compared to microporous (< 5 nm pore diameter)Raney nickel, which demonstrates at most 1.5% surface utilization, 3DOM solids offerexciting prospects for the development of new electrode materials.

Here, we explore the viability of 3DOM solids as nanostructured electrodes forlithium-ion batteries by examining the fabrication, characterization, and electrochemicalperformance of 3DOM Li4Ti5O12, a commonly cited anode for lithium-ion batteries. Indoing so we have investigated the molecular chemistry of inorganic-organic precursorsfor the synthesis of new 3DOM solids.

R3M6+xAl26T: Cubic Intermetallic Phases with a Stuffed BaHg11 Structure grownfrom Aluminum Flux

S. E. Latturner, D. Bilc, S. D. Mahanti and M. G. KanatzidisDepartment of Chemistry and Department of Physics, Michigan State University, East

Lansing, MI 48824

Elements such as transition metals and silicon are often added to aluminum alloysto optimize their properties. Much of the improved behavior is due to the formation of asyet unexplored multinary intermetallics within the aluminum matrix; investigation ofthese adventitious compounds is necessary to understand and control the characteristicsof the bulk alloy. With this in mind, a wide variety of new intermetallic materials with acubic, stuffed BaHg11 structure have been synthesized by the combination of a rare earthor alkaline earth metal R, a late transition metal M, and an early transition metal T in anexcess of molten aluminum. These compounds, with formula R3M6+xAl26T, grow fromthe aluminum flux as large spheroid crystals. Due to the highly reducing nature ofaluminum, it is also possible to synthesize these compounds using complex oxideprecursors such as perovskites; for example, the combination of SrTiO3 and Au in excessAl produces Sr3Au7Al26Ti. Structural characterization of R3Au6+xAl26T compounds bypowder and single crystal X-ray diffraction indicates that the unit cell varies with theradii of the early transition metal T and the rare earth / alkaline earth R as expected.Varying amounts of disorder and trends in partial occupancies of the stuffed site—the sitethat is vacant in the parent compound BaHg11—are also indicated by the diffractionstudies of this family of compounds. Magnetic susceptibility data reveals that thetransition metal atoms in these materials do not possess local magnetic moments.

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Novel inorganic-organic hybrid materials containing [Nb6Cl12(CN)6]4− cluster

Bangbo Yan and A. LachgarDepartment of Chemistry, Wake Forest University, Winston-Salem, NC 27109

Hybrid inorganicorganicmaterialsareof greatinterestdueto their potentiallyusefulpropertiesas catalystsor separationsagents.Our work in this area focuseson thesynthesisof extendedsolidsbasedon octahedral[Nb6X12]n+ (X=Cl, Br, O) clustersusingtransition metal complexes as bridges. Here we report two novel compounds:[Nb6Cl12(CN)6{Cu(en)2} 3]2[Nb6Cl12(CN)6] (1) and [Nb6Cl12(CN)6{Zn(en)}2] (2). Crystalsof 1 were preparedby layering aqueoussolutionsof [N(CH3)4]4[Nb6Cl12(CN)6] with asolution of Cu(en)2Cl2 in ethanol. The structure of 1 consists of a discrete [Nb6Cl12(CN)6]4-

cluster, and two [Nb6Cl12(CN)6{Cu(en)2} 3]2+ units in which the cluster unit[Nb6Cl12(CN)6]4- connectsto three{Cu(en)2} 2+ groupsthat adopta facial arrangementonthe octahedral cluster. Compound 2 was synthesized through the reaction ofNa4[Nb6Cl12(CN)6] andZn(en)[ClO4]2 in H2O/EtOH solution.The crystal structureof 2contains[Nb6Cl12(CN)6]4− clusterslinked by {Zn(en)}2+. Eachcluster [Nb6Cl12(CN)6]4-

connectsto six {Zn(en)}2+ groups,andeach{Zn(en)}2+ groupconnectsto threeclusters[Nb6Cl12(CN)6]4− to form layers running parallel to the ab plane. Within the layer,puckeredringsareformedby three[Nb6Cl12(CN)6]4− clustersandthree{Zn(en)}2+ groups.The {Zn(en)}2+ groupsare projectingaboveand below the layer into the rings of theadjacentlayers.Crystaldatafor 1: P3,a = 20.550(4)Å, c = 8.780(3)Å, V = 3211.1(13)Å3, dcalc= 2.335g/cm3, Z = 3, R1 = 0.098,wR2 = 0.186;for 2: P-3m1,a = 1.891(3)Å, c= 8.721(3) Å, V = 895.8(4) Å3, Dcalc = 2.565 g/cm3, Z = 1, R1= 0.062, wR2 = 0.160.

Deltahedral Germanium Clusters: Oligomerization and Functionalization

Slavi C. SevovDepartment of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN

46556

Deltahedralgermaniumclustersof nine atoms,Ge94-, havebeencharacterizedinbinarycompoundswith thealkali metals,i.e. A4Ge9. Thesecompoundsdissolvereadily

15

in ethylenediamine and provide the corresponding nine-atom clusters in solution. Itseems that the clusters in solution carry different charges of -2, -3 and -4, and are inequilibria between themselves and solvated electrons. Clusters with different charges canbe crystallized from such solutions by using countercations with appropriate sizes andshapes that depend on the sequestering agents for the alkali-metal cations.

The use of soft oxidizing agents such as EPh3 and E'Ph4 where E = P, As, Sb, Biand E' = Ge, Sn, Pb leads to either oxidative addition and formation of species such as

[Ph2E–Ge9–EPh2]2-, [Ph3E'–Ge9]3-, and [Ph3E'–Ge9–E'Ph3]2- or oxidative coupling to

form [Ge9–Ge9]6-, [Ge9=Ge9=Ge9]6-, and [Ge9=Ge9=Ge9=Ge9]8-. The synthesis andcharacterization of these and other novel species will be discussed in the talk.

POSTER PRESENTATIONS

Near Room-Temperature Ferromagnetism Found in ZnSnP2:Mn

Single Crystals Grown via Sn-Flux

Jennifer A. Aitkena, Georgy Tsoib, Lowell Wengerb and Stephanie L. Brocka

aDepartment of Chemistry, Wayne State University, Detroit, MI 48202. bDepartment of Physics, Wayne State University, Detroit MI 48202.

As we move further towards miniaturization of electronic and memory devices welook for multifunctional materials. One such area emerging from this rationale is thefield of spintronics, where researchers wish to exploit not only the charge carriers of amaterial but also the spin of those charge carriers. A material with room-temperatureferromagnetism and an existing technology base for use in applications would be an idealcandidate for spin-based devices.

Near room-temperature ferromagnetism has recently been discovered in severalMn-doped chalcopyrite materials, namely CdGeP2:Mn, ZnGeP2:Mn, ZnSnAs2:Mn andZnGeAs2:Mn. Although these materials lack an existing technology base, theirferromagnetic behavior at practical temperatures makes them possible candidates forroom-temperature spintronic devices.

Here we report a novel dilute, magnetic semiconductor (DMS) chalcopyrite,ZnSnP2:Mn. The material is grown as relatively large single crystals, 3 x 1 x 1 mm, inliquid Sn at 650 ºC. Although liquid Sn has been used for many years to growchalcopyrites and other types of materials, this is the first time that a DMS material hasbeen produced in this way. The compound undergoes an antiferromagnetic toferromagnetic transition at very low temperatures and a ferromagnetic to paramagnetictransition near room temperature. Here we will report the optical, thermal and magneticproperties of this promising, new DMS material.

16

Synthesis and Characterization of Cadmium Selenide Aerogels

Indika U. Arachchige, Jaya L. Mohanan, and Stephanie L. Brock*Department of Chemistry, Wayne State University, Detroit, Michigan 48202

Aerogels are a unique class of inorganic polymers that have low densities, largeopen pores and high inner surface area. This results in interesting physical properties aswell as a wide variety of potential applications as catalysts, sensors and novelelectrochemical device components. So far, a great deal of research has been conductedon aerogels based on single and mixed metal oxides. However, non-oxide aerogels, withthe exception of carbon aerogels, are virtually nonexistent. We have recently synthesizeda pure chalcogenide based semiconductor aerogel of CdS from controlled aggregation ofprimary particles followed by super-critical fluid extraction. In this study, we seek toexplore the generality of the method and report herein the synthesis of CdSe aerogels.Preliminary characterization of CdSe aerogel is done using X-ray diffraction,transmission and scanning electron microscopy, surface area analysis, optical absorption,luminescence and UV-visible spectroscopy. The effect of synthetic parameters on theparticle size, morphology, surface area, and optical properties will be discussed.

Towards Synthesis and Characterization of Homogenous Transition Metal ArsenideNanoparticles

Palaniappan Arumugam and Stephanie L. Brock*

Department of Chemistry, Wayne State University, Detroit, MI-48202

Bulk transition metal arsenides, such as CoAs and FeAs, are studied extensivelybecause of their technological importance as semiconductors and magnetic materials,respectively. In recent years it has been shown that physical properties of materials canbe tuned by controlling the size of the particles to the nanometer regime (1-100 nm). Todistinguish properties that are inherent to nanoscale structures from those of bulk orpolydisperse materials, synthesis of monodisperse nanoparticle samples is essential. Todate, the size dependent properties of transition metal arsenide particles have not beenexplored, perhaps because of the unavailability of reliable synthetic methods to producenear monodisperse nanoparticle samples of these phases with control of stoichiometry.To address these concerns, we have recently developed a new synthetic methodology toproduce transition metal phosphides based on reduction of transition metal phosphates.The application of this methodology to arsenide phases of Fe, Co, and Ni will bediscussed. Specifically, the synthesis and characterization of transition metal arsenatenanoparticles will be described along with our attempts to reduce these materials, eithersupported on substrates or in solution.

Non-centrosymmetric Ba3Ti3O6(BO3)2

Hyunsoo Park, Anthony Bakhtiiarov, Wei Zhang, Ignacio Vargas-Baca and JacquesBarbier.

Department of Chemistry, McMaster University, Hamilton, Canada.

17

The compoundpreviously reportedas Ba2Ti2B2O9 (Millet, Roth and Parker, J. Am.Ceram. Soc. 69, 811-814, 1986) has been reformulated as Ba3Ti3B2O12, orBa3Ti3O6(BO3)2. Small single crystals have been recovered from a melt with acompositionof BaTiO3:BaTiB2O6 (molar ratio) cooledbetween1100 and 850°C. Thecrystal structure has been determinedby X-ray diffraction: hexagonalsystem,non-

centrosymmetricP-62mspacegroup,a = 8.7377(11)Å, c =3.9147(8) Å, Z = 1, wR(F2) = 0.039 for 504 unique

reflections. The Ba3Ti3O6(BO3)2 structure consists of aframework of triple [001] octahedralchains bridged by

orthoborate groups with Ba2+ cations occupying 13-coordinatedsitesin irregularpentagonalchannels(cf. Figure).

Ba3Ti3O6(BO3)2 is isostructuralwith K3Ta3O6(BO3)2 (Abrahams,Yontz, Bernstein,RemeikaandCooper,J. Chem. Phys. 75, 5456-

5460,1981)andwith the high-T form of K3Nb3O6(BO3)2 (Becker,BohatyandSchneider,Cristallogr. Rep. 42, 213-217,1997).A bondvalenceanalysisofthe Ba3Ti3O6(BO3)2 structurerevealsthe presenceof residualbondstrainwhich may beassociatedwith theapparentmarginalstability of Ba3Ti3O6(BO3)2 ascomparedto BaTiO3

and BaTiB2O6. Attemptsto extendthis structuralseriesvia other substitutionreactionshaveso far beenunsuccessful.Preliminarymeasurementsof nonlinearoptical propertieson microcrystallinesamplesshow that the secondharmonicgenerationefficiency ofBa3Ti3O6(BO3)2 is about 18 times larger than that of KH2PO4.

Exploring Octahedral Tilting Distortions in A 2MM’O 6 Variably Ordered DoublePerovskites Using Neutron Powder Diffraction.

Paris W. Barnes*, Michael W. Lufaso‡, Patrick M. Woodward*, and Pavel Karen†. *-Department of Chemistry, The Ohio State University, Columbus, OH, 43210; ‡-Ceramics

Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8520; †-Department of Chemistry, University of Oslo, 0315 Oslo, Norway.

The perovskite structure with 1:1 M-site cation ordering (or double perovskite;A2MM’X 6) is a well known and extensively studied structure type in solid statechemistry. Theidealdoubleperovskitehascubicsymmetry,but manyaredistortedfromthe ideal structure. Structuraldistortionsseenin perovskitesare causedby electronicfactors (i.e., Jahn-Teller ions), M-cation displacementfrom the center of the MX 6

octahedra(i.e., cationswith a stereoactivelone pair of electrons),andmost commonly,octahedraltilting. Tilting of the octahedrawithin the perovskitestructure leads toloweringof its symmetry. A major factor that influencesthedegreeof octahedraltiltingin a givencompoundis thenatureof thecuboctahedralA-cation. Perovskiteswith Ba2+

as the A-site cation typically exhibit cubic symmetry and those with Ca2+ haveorthorhombicor monoclinicsymmetry. Changes(or lack of) in spacegroup symmetryfor A = Ba2+ andCa2+ areofteneasilyseenin theX-ray powderdiffraction data(XRPD)of their respectivecompounds. Yet, compoundswith A=Sr2+ are prone to subtleoctahedraltilting distortionsthat arenot readily seenin XRPD, so manyaremistakenlyassignedto theincorrectspacegroup. In this study,tendoubleperovskiteswith A = Sr2+

(M3+ = Al, Sc,Cr, Mn, Fe,Co, Ga,Y; M5+ = Nb, Sb),Ca2CrTaO6, andBa2YNbO6 wereexaminedusingRietveldrefinementsof neutronpowderdiffraction data(NPD) in orderto appropriatelydiscerntheir respectivecrystallographicsymmetry. Theapproachtakenfor determiningappropriatepossiblespacegroups,thereliability of peaksplitting seeninthe XRPD data for determiningspacegroup symmetry, the extent of M-site cation

18

ordering, and the degree of octahedral tilting seen in this family of compounds will bediscussed.

Electronic structure of K2Bi8Se13

Daniel I Bilc, P. Larson1, S. D. Mahanti and M. G. Kanatzidis2

Department of Physics and Astronomy, Michigan State University, E. Lansing, MI48823, 1Naval Research Laboratory, Washington D. C.,

2Department of Chemistry, Michigan State University, East Lansing, MI 48823

A novel material belonging to the class of complex Bi-Te-Se systems, K2Bi8Se13 , hasbeen discovered at MSU and it shows great potential for thermoelectric performance.This compound forms in two distinct phases α-K2Bi8Se13 (triclinic with space group P-1)and β-K2Bi8Se13 (monoclinic with space group P 21/m). The β-phase has structuraldisorder, there are four sites with mixed K/Bi occupancy. To understand the electronicproperties of these two different phases we have carried out electronic structurecalculations within ab initio density functional theory (DFT) using full potentiallinearized augmented plane wave (LAPW) method. The α-phase is found to be asemiconductor with an indirect band gap of 0.47eV. For the β-phase we have chosen twodifferent ordered structures with extreme occupancies of K and Bi atoms at the "mixedsites". Both systems are semi-metals. To incorporate the effect of mixed occupancy wehave chosen a 1x1x2 supercell with an alternative K/Bi occupancy at the "mixed sites".This system is found to be a semiconductor with an indirect gap of 0.38eV. We haveshown that the mixed occupancy is crucial for the system to be a semiconductor becausethe Bi atoms at the "mixed sites" stabilize the Se-p orbitals of the nearest neighbors Seatoms by lowering their energy. We find a strong anisotropy in the effective mass nearthe conduction band minimum, with the smallest effective mass along the mixed K/Bichains (parallel to the c-axis) through Bi-Se framework. This large anisotropy suggeststhat β-K2Bi8Se13 has a great potential for a n-type thermoelectric material. *Supported by the office of Naval Research and DARPA through grant N00014-01-1-0728.

Synthesis and Structural Characterization of Novel Ternary Phases in theSystems RE-TM-Ga (RE = Ce, Yb; TM = Rh, Ir, Pd, Pt)

Svilen Bobev,ª John L. Sarrao,b Joe D. Thompsonb and Zachary Fiskc

a Los Alamos National Laboratory, LANSCE-12, MS-H805, Los Alamos, NM 87545b Los Alamos National Laboratory, MST-10, MS-K764, Los Alamos, NM 87545c National High Magnetic Field Laboratory (NHMFL), Florida State University,

Tallahasse, FL 32306

Several novel ternary phases RE-TM-Ga (RE = Ce, Yb; TM = Rh, Ir, Pd, Pt) weresynthesized in high yields by standard solid-state techniques from pure elements atelevated temperatures. Pure gallium, intended as a solvent, was used in excess and largesingle crystals of the title compounds were successfully grown from these solutions.Their crystal structures were determined by both single crystal and powder X-Raycrystallography. All Rh and Ir compounds crystallize in a new hexagonal structure types

19

(relatedto the YPt2In-type), featuringcorrugatedTMGa2-layersstackedin a typical hcpsequence(ABAB) alongthec-axisandseparatedby RE2Ga3-layers. Thelatterareheavilydisorderedin thexy planeandthis phenomenonappearsto bea purelystatisticaleffect -no evidencefor ordering in an a

�3 × a

�3 supercell was found. More likely, the

disorderedRE2Ga3-layerscan “slip” easily in the xy plane,creatingstackingfaults andhence– extremedifficulties for thecorrectstructuredeterminations.On the otherhand,employingPd in placeof Rh or Ir, yields ternaryderivative of the BaAl4-type (body-centeredtetragonalspacegroup)with randomstatisticaldistributionof PdandGaon thetwo crystallographicsites. Lastly, Pt-basedanalogscrystallizein the known hexagonalstructure type Ce2Pt6Ga15 with double PtGa2-layers, which are again separatedbydisorderedRE2Ga3-layers. Most of the title compoundsexhibit long-rangemagneticordering,while someof them, typically the Ir-basedphases,do not show any signsofmagneticorderdownto 2K. Theresistivities,measuredin thetemperaturerange2–290K(with the current applied along the c-axis of the crystal) are metallic and relativelyfeatureless. More careful and precise property measurements are currently underway.

Local Structural Study of Colossal Dielectric Constant CaCu3Ti4O12 Using the Atomic Pair Distribution Function Technique

E. S. Bozin (1), V. Petkov (2), P. W. Barnes (3), P. M. Woodward (3), S. J. L. Billinge (1),S. D. Mahanti (1), and T. Vogt (4)

(1) Department of Physics and Astronomy, Michigan State University(2) Department of Physics, Central Michigan University

(3) Department of Chemistry, Ohio State University(4) Physics Department, Brookhaven National Laboratory

Cubic insulating CaCu3Ti4O12 has attractedsignificant attention as it exhibits a giantdielectricconstantresponsewith a very unusualtemperaturedependence.We reportonlocal structural studiesusing the atomic pair distribution function approachover thetemperaturerangewherean enormousreductionof the dielectric constantis observed.Although thereis no indicationof a structuralphasetransition,the local structuralstudyrevealsan unusualtemperaturedependencefor the atomic displacementparametersofCa/Cu sublattice suggestingpresenceof the local disorder. Temperaturedependentmodelingof the structure,usingbondvalenceconcepts,suggeststhat the calciumatomsbecomeunderbondedbelow approximately260 K, which providesa rationalefor theunusually high Ca displacement parameters observed at low temperature.

HIGHLY REDUCED POLYOXOMETALATES WITH AN UNUSUALARCHITECTURE

Nathalie Calin and Slavi C. SevovDepartment of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN

46556

Polyoxoanionsarea uniqueclassof metal-oxygenclusterswith a multitudeof structuresand many interestingpropertiesin different fields including catalysis,medicine,and

20

materials science. Although the first polyoxometalateswere reported almost twocenturiesago,themajority of specieshavebeenstructurallycharacterizedonly recently.The mechanismof formation of polyoxoanionsis still not well understoodand mostlydescribed as self-assembly. Several strategies for the construction of specificarchitecturesfrom molecular building blocks have beendescribedin recentyears.Apopular strategyin the realizationof such materialsinvolves the use of hydrothermalsynthesis and structure directing templates.The successof this strategy can bedemonstratedby the developmentof low-dimensionalas well as three-dimendionalmicroporoustransition-metalphosphates.We are interestedin the synthesisof extendedhybrid structuresconstructedfrom metal organic derivativesof polyoxometalatesanddiphosphonateligands. This has led to the discovery of a novel mixed-valencemolybdodiphosphonateand its one- and two-dimensional derivatives, and a newpentamolybdodiphenylphosphonate decorated by transition-metal complexes.

Lu8Te and Lu7Te. Novel Substitutional Derivatives of Lutetium Metal

Ling Chen and John D. Corbett *Department of Chemistry, Iowa State University, Ames, Iowa, 50011

Monocrystalsof Lu8Te aresynthesizedby disproportationof Lu7Te at 1000– 1200°C orby directreactionof Lu plusLu2Te3 at 1000°C for two weeks. Lu7Te is producedby arcmeltingof a suitableLu–Lu2Te3 mixture,with goodcrystalsbeingformedby subsequentannealingat 1300°C. The structuresof Lu8Te (P6 2m, Z = 1) andLu7Te (Cmcm,Z = 4)exhibit h.c.p.packing(AB···) of distorted,not closepacked,layersalongoneshortaxis (�

c , �

a , respectively).

PuckeredLu, Te layersarestackednormalto (010)or (001) in six or eight layer repeatsequences,with Te substitutingfor every third orevery other Lu in every third or fourth layer, respectively.Strong Lu–Te bonding isindicated. Both Tesubstitutionsdecreasethevolumeperatomfrom thatin h.c.p.Lu andalso decrease the coordination number of all atoms from 12 to 9–11.Acknowledgement:this work is supportedby Dept. of Energy, National ScienceFoundation, Grant DMR-0129785.

21

Structure and Magnetic Property of Heavy Metal Ba-(In or Tl)-Bi Zintl PhaseSystem

Ara Cho and Slavi C. Sevov

Department of Chemistry & Biochemistry, University of Notre Dame

Zintl phases have been studied for many years. Zintl compounds have alkali oralkaline-earth metals as electropositive donors and p-block elements as electronegativeacceptors. So Zintl phase compounds are classically called “polar intermetalliccompounds”. The electron transfer from the donor to the acceptor allows the latter tofulfill the octet rule. To do so, the p-block elements can form 2c-2e- bonds between eachother and/or carry lone pairs of electron. Zintl phases are diamagnetic but in some rarecases can exhibit a metallic character due to delocalized extra electrons.

In this poster, we will discuss the structure and properties of heavy metal Zintlphase system: Ba-(In or Tl)-Bi. They are allowed in zintl concept but they have metalliccharacters as a rare case.

New low dimensional NaM1-xP2S6 thiophosphates (M = Cr, V) : synthesis, structuresand exfoliation properties

S. Coste(1), E. Gauthier(1), E. Michel(1), R. Brec (1), S. Jobic (1) and M. G. Kanatzidis(2)

(1)Laboratoire de Chimie des Solides, Institut des Matériaux Jean-Rouxel, UMR 6502CNRS, Université de Nantes, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3,

France (2)Department of Chemistry and Center for Fundamental Materials Research,Michigan State University, East Lansing, Michigan 48824

A number of quaternary alkali (A) and transition metal (M) chalcogenophosphateswith crystal formula AwMxPySz (M = Cr, V)i have been recently prepared employing thetraditional ceramic route from direct combination of the reagents in stoichiometricamounts. A potentially interesting property of some low-dimensional compounds is theirexfoliation in polar solvents. A prime example of this behavior is LiMo3Se3

ii and thetransition metal thiophosphate compounds KNiPS4

iii and APdPS4iv. These compounds are

composed of infinite anionic 1/∞[Mo3Se3], 1/∞[NiPS4] and 1/∞[PdPS4] chains respectively.While the 1/∞[NiPS4] chains undergo an autofragmentation under the action of the solventto give rise to unprecedented discrete crown-shaped [Ni3P3S12]3- anions v, the 1/∞[PdPS4]and 1/∞[Mo3Se3] chains are maintained in solution 48, vi inducing complex fluid and liquidcrystal behavior, respectively. Because of the potentially interesting physical propertiesand chemical reactivity of low dimensional materials in solution, we recently embarkedon a quest for new soluble alkali metal containing chain-like thiophosphates withmagnetically active transition metal elements (i.e.V3+ (d2, S=1) and Cr3+ (d3, S=3/2)). Suchsystems would be highly worthy of investigation because dilute nematic suspensionsmight be oriented and controlled by applying magnetic or electric fields. We report herethe preparation of 1D-NaCrP2S648

c and mixed-valent 1D-NaV0.837(6)P2S6vii compounds,

their crystal structures and their unusual exfoliation which gives rise to complex fluidbehavior. The gel forming properties in solution for 1D-NaV0.837(6)P2S6 are also reported.

22

23

Rational Synthesis of New Ternary Pnictides and Chalcogenides using a StructureMap

S. Derakhshan, H. KleinkeUniversity of Waterloo, Department of Chemistry, Waterloo, ON, Canada N2L 3G1

Recently, we developed a structure map for metal-rich transition metal pnictidesand chalcogenides M2Q, using a structural factor as the ordinate, namely the averagedcoordination number of the Q atoms <C.N.(Q)>, and a combination of atomic factors asthe abscissa, namely principal quantum numbers, valence-electrons, and radii. M standsfor all metal atoms of groups 3-5, and Q for the elements of the groups 15 and 16,excluding the elements of the second period, N and O. The map includes the ternaries(M,M')2Q and M2(Q,Q').

This structure map has subsequently been used to predict some crystal structurescorrectly: both new arsenides ZrTiAs and ZrVAs were supposed - based on the map - toform the La2Sb type, which we then confirmed via single crystal structure studies. Thiswas particularly interesting, as these were the first transition metal arsenides to form thistype.

On the other hand, the phosphide ZrTiP was reported before to crystallize in theCo2Si type. According to the structure map, the Hf arsenides HfTiAs and HfVAs andphosphides HfTiP and HfVP should all adopt the Co2Si type as well. Since only the lastone, HfVP, was known (which does form the Co2Si type), we proceeded with trying toprepare the other three Hf pnictides. All of them were prepared, and our structureinvestigations proved once more the usability of our structure map: all of these four Hfcompounds occur in the Co2Si type, as predicted. This contribution deals with thesecompounds, in particular concentrating on the differences to the Zr pnictides.

Synthesis and Characterization of Noncentrosymmetric Chain Compounds,A3M2AsSe11 (A=K, Rb, Cs; M=Nb, Ta)

Junghwan Do and Mercouri G. KanatzidisDepartment of Chemistry and Center for Fundamental Materials Research

Michigan State University, East Lansing, MI 48824

Several noncentrosymmetric quaternary niobium and tantalum selenoarsenates,A3Nb2AsSe11 (A=K, Rb, Cs) and K3Ta2AsSe11, were synthesized by thepolychalcoarsenate flux method. All the compounds crystallize in thenoncentrosymmetric monoclinic space group Cc. All the structures are comprised of thesame type of chain anions, [M2AsSe11]3- (M=Nb, Ta) separated by alkali metal cations.Each of the two crystallographically independent niobium or tantalum atoms in theanionic chain is coordinated by seven selenium atoms in a distorted pentagonal prismaticarrangement. Two pentagonal prisms that contain one M4+ ion coordinated by 3Se2- +3Se2

2- and the other M4+ ion coordinated by 2Se2- + 3Se22- share a common face to form a

[M2Se5(Se2)3]8- dimeric core that propagates along the chain through a pyramidal [AsSe3]1-

anion to complete a [M2Se2(Se2)3(AsSe3)]3- anionic chain. The As3+ cations withnonbonded electron pairs play an important role in the formation of thenoncentrosymmetric compounds. The origin of noncentrosymmetric space group Cc ofthe compounds may be understood by examining the structure concerning the lone pairpolarization arrangement of As3+ cations. The structures of the compounds weredetermined by single crystal X-ray diffraction. The physical properties of the compounds

24

were studiedby UV-Vis spectroscopy,Ramanspectroscopyand Differential ThermalAnalysis.

Optical properties of CeBO3 and CeB3O6 compounds: first-principle calculationsand experimental results

Goubin F.a, Jobic S.a, Rocquefelte X.a, Brec R.a, Montardi Y.ba Institut des Matériaux Jean Rouxel, 2 rue de la Houssinière, BP 32229, 44322 Nantes

Cedex 03, Franceb Rhodia Electronics and Catalysis 52 rue de la Haie Coq, 93308 Aubervilliers, France

In thequestof secondgenerationinorganicUV absorbers,Ce(III) containingcompoundshave beensynthesizedand their optical propertiesdeterminedby UV-visible diffusereflectancemeasurementsand electronenergy-lossspectroscopy(EELS). The opticalabsorptionmechanismandthedielectricconstantwereinvestigatedusingfirst-principlesdensity functional theory.The cerium borates o-CeBO3, m-CeBO3 and CeB3O6 have been shown to be isostructuralto their lanthanum derivatives. It has been evidenced that a Ce3+ 4f-5d transition isresponsible for a weak absorption peak around 3.5 eV while the O2p-Ce5d chargetransfer gives rise to a strong absorption peak around 7 eV. Starting from selfconsistentfull potential LAPW calculations, the dielectric tensors of the three compounds werecomputed and compared to experimental data. It results a satisfactory fit between theobserved and the calculated extinction coefficient k and the refractive index n. Comparedwith O2p-Ce5d charge transfer intensity, an unexpected low k value associated to the Ce3+

4f-5d transition was found.

Crystallographic, Electronic and Magnetic Studies of ξ2-GaM (M = Cr, Mn or Fe):From Antiferromagnetism to Ferromagnetism

Olivier Gourdon, Sergey Bud’ko, Darrick Williams and Gordon J. Miller*

Department of Chemistry and Ames Laboratory, US Department of Energy,Iowa State University, Ames, Iowa 50011-3111

The study of the crystal structure, electronic structure and magnetic properties of theξ2-GaM (M = Cr, Mn or Fe) alloys is motivated by the recent reinvestigation of thecrystallographic Al8Cr5 structure type of ξ2-GaMn. Moreover, previous crystallographicstudies shown that the Al8Cr5 structure type can be also adopted by GaCr and GaFebinaries alloys. Band structure calculations using self-consistent spin-polarized TB-LMTO method were performed to understand the electronic structure and the magneticproperties expected. The calculations show than from Cr to Fe a change of the magneticinteractions from an antiferromagnetic coupling to a ferromagnetic coupling is observedand susceptibility measurements confirm this evolution.

25

Experimental and theoretical studies of two new ternary intermetallic compounds inthe Ln (Ln=La and Ce)-Nickel-Aluminum phase diagrams: Ce4Ni6Al23 and

La4Ni5.8Al22.2

Delphine Gout, Evan Benbow, Olivier Gourdon and Gordon J. Miller*

Department of Chemistry,Iowa State University, Ames, Iowa 50011-3111

The Al-rich portion of the ternary Ce-Ni-Al has been investigated and a new ternaryphase of composition Ce4Ni6Al23 has been synthesized. The crystal structure has beensolved by single X-Ray diffraction. Band structure calculations, using TB-LMTO-ASAmethod, have been performed to understand its electronic structure and the results arediscussed in connection with others Ce-Ni-Al intermetallic compounds which possesssimilar local environments and similar magnetic dense-Kondo behavior or possiblevalence fluctuation behavior. Analysis from Crystal Orbital Hamilton populations(COHP) reveal that the Al-rich compounds may be considered as “polar intermetallic” asthe Fermi level coincides to the separation of bonding and antibonding states of the Ni-Alframework Sincethe Ce-f orbitals may play a role in theseproperties,the Lanthanum-Nickel-Aluminumsystemhasbeenalsoinvestigated.However,the sameexperimentsinthis systemgive a new structuretype with a formulationLa4Ni5.8Al 22.2. The structureofthis new compoundis quite interestingsinceit exhibits in the centerof the unit cell alarge open cavity which could be filled by a guestatom such as hydrogenor smallalkaline metals.

Studies of the Electronic Properties of BaV10O15: Crystallographic Phase Transition,Electrical Transport and Magnetic Properties

Craig Bridges and J.E. Greedan*Brockhouse Institute for Materials Research and Department of Chemistry,

McMaster University, Hamilton L8S 4M1 CANADA

BaV10O15 canberegardedasa “Ba-doped”variationof V2O3 wheretheBa ionssubstitutein theclosepackedoxidelayers.TheBa ionsdirecttheoccupationof theoctahedralsitesby the V2+/V3+ ions. The resultingstructureis closely relatedto that of V2O3 but withsubtledifferences.A remarkablecrystallographicphasetransitionoccursat 125K fromCmcato Pbca,which, it will beargued,is drivenin partby V-V bondformationresultingin oneof theshortestV-V distances,2.5334(5)Å, known in vanadiumoxide chemistry.The phasetransitionis reflectedin the transportproperties,both resistivity andSeebeckeffect. A complexmagneticphasetransitionsetsin below Tc = 42K as confirmedbyneutronscatteringandspecificheatstudies.The V-sublatticeis geometricallyfrustratedand the exchangeinteractionsarestrongly antiferromagnetic,θ = -1141(23)K. Only avery small fractionof theentropyis removedbelowTc, ~ 4 %, andit is likely thatonly afraction of the spins are ordered.This interpretationis supportedby the neutrondata.These results point to a very heterogeneous magnetic ground state for this material.

26

HYDROTHERMAL SYNTHESIS OF THREE DIMENSIONAL STRUCTURESUSING METAL OXIDE-FLUORIDES AND NEUTRAL BIDENTATE LIGANDS.

Paulette R Guillory, Heather K Izumi, Duward F Shriver, Kenneth R. Poeppelmeier*Northwestern University, Department of Chemistry, Evanston, IL 60208-3113

Non-centrosymmetric materials are of interest because their symmetry-dependantproperties, such as piezoelectricity, ferroelectricity, and second order non-linear optical(NLO) behavior, are the basis of numerous technological applications. LiNbO3, a wellknown inorganic NLO material, exhibits an out-of-center distortion in the individual[NbO6/2]- octahedra postulated to cause the non-linear response. These out-of-centerdistortions are replicated by metal oxide fluoride anions (MOF5

-2), where the polardistortion in the octahedra is inherent in the molecule itself, and not a product of a phasetransition. Compounds constructed with these metal oxide fluoride anions havehistorically crystallized without internal disorder, or crystallized with order but with ananti-parallel arrangement of the anions, forming a centrosymmetric compound.Understanding the mechanism of crystal formation may enable the synthesis of a non-centrosymmetric compound where the octahedral anions crystallize without disorder, andwithout anti-parallel arrangement.

Metal oxide fluoride anions, particularly TaOF5-2, NbOF5

-2, MoO4F2-2 and WO4F2

-2

are easily synthesized using hydrothermal synthesis. The metal oxides are reacted with ahydrofluoric acid solution inside of Teflon pouches in a stainless steel, constant-volume reactor. The reactions are monitored and studied using a composition spacediagram, similar to a ternary phase diagram, where the products are related to the initialmole fractions of the reactants. The molar ratio of each reactant is recorded, with theother variables (temperature and amount of solvent) held constant.

One method to control the internal ordering of the metal oxide fluoride (i.e.[NbOF5] 2-] is through the use of a neutral bidentate ligand to coordinate to the cation(i.e. Cd2+) in a cis fashion. This cis coordinate cationic complex will bond to the oxide onthe niobium, creating an ordered structure. If the anions are also in parallelarrangement, the structure will be non-centrosymmetric. This area is being exploredusing early transition metal (Nb, Ta, Mo, W) oxide fluorides, late transition metal (Ni,Cu, Ag, Zn, Cd) cations, and neutral ligands (2,2’-dipyridyl amine).A polymorph of CuNb(Pyridine)4OF5 using the anionic NbOF5-2, and cationic Cd+2 wassynthesized. The basic chain of the two polymorphs is identical, but differ in packing,and also the ordering of the oxide and fluoride ligands in the octahedral [NbOF5] 2- unit.Further study of this polymorphism will lead to an understanding of synthetic methodsand allow a rational synthetic method to be devised to construct these materials.

Exploring Fe-rich intermetallics with the NaZn13

structure-type : R(FexSi

1-x)13

(R

= La, Ce)

���������� ��������������������������! #"$�%"'&)(*�+� ,%&.-0/1� "2�

A growing number of intermetallic compounds, called “polar intermetallics”,have been synthesized and studied for relationships between their chemical bonding-structure- properties. Polar intermetallics involve the combinations of

&�3�&546"�-'��7%�8/1� "9� ,%&����:;&�3 &46"9-'�.�%&��%"<� ,%&=�>& "$�83?/%@8ACB%&;&83�&46"9-'�.7��8/1� "<� ,%&D�>& "$�8384E���+/1�F/G"0/H� IJ�K3��6�83F�MLN�83��6�83����%&

27

����������� �������������������������������������� � �!�����"���#�$%����� &'��(�'��� )��*�����+���,�-�/.0� .1'23�0���)���&546�0��&�78 �9��� ��&�����:�����<;=�/&>�?�A@�����7� ��.CB he structuresof polar intermetallicsoften cannotberationalizedby anysimpleelectroncountingrules,suchasWade’srulesor theOctetrule,but do show optimum bonding from theoretical calculations. Theoverallgoalsof my researchareto extendtheconceptsof polar intermetallicsto latetransition metals. To accomplish this goal, I have focused on the synthesisandcharacterizationof iron-based intermetallics becauseof their large collections ofcompounds. Especially,I havefocusedon studyingR(Fe,Si)13, (R= La, Ce,Ba, Sr) compoundswithstructures related to the cubic NaZn13-type. I will report onLaFe13-xSix(X= 1.04-3.4) with cubic NaZn13 structureand CeFe13-xSix(X= 4-4.5)

which has a tetragonalmodification of NaZn13 –type as studiedby single crystal andpowder x-ray diffraction.

Theoretical calculations on models of various icosahedral clusters provide clues tounderstand my structural observation. Preliminary theoretical results will be reported.Reference :1. D � &�(�E�F����"G3H'��� ���/I2KJ�J��0.�LC�>M���.�N'�����?.1�O�P�Q+R�S�TU�S�V�O�W�>XYY[Z2. A. Fujita, et. al., Phys. Rev. B, 65, 014410, 2002 3. Cao, L.Z., J. Alloys. Compd. 2002, 336, 18

Solid State Synthesis and Characterization of the [C10N12]4- Anion.A Possible Precursor for the Synthesis of Carbon-Nitrogen Networks

Lykourgos Iordanidis and Omar M. YaghiMaterials Design and Discovery Group, Department of Chemistry, University of

Michigan, 930 N. University Avenue, Ann Arbor, MI 48109

Over the last two decadestherehavebeenconsiderableresearchefforts in thesynthesisof carbonnitridenetworksdueto their potentialashard,lightweight,andthermallystablematerials.The resultsof theseefforts areoften controversial,mainly dueto the lack ofdefinitive structuraldata.In anattemptto obtaina betterinsightof theabovesystems,wedecidedto studythetrimerization/polymerizationreactionsof NaN(CN)2. ThereactionofNaN(CN)2 at ~600°C producesyellow-brownrodswith thecompositionNa4C10N12. Thestructureof Na4C10N12 consistsof [C10N12]4- moleculesarrangedin columns,in a “herring-bone” pattern.The [C10N12]4- moleculesconsistof a three-memberedfused-ringsystemC7N6 and threeterminal N-C≡N groupsattachedin the threecornersof the fused-ring.Na4C10N12 is stablein water whereit dissolvesvery easily yielding a pale yellow basicsolution.The [C10N12]4- moleculecanberecrystallizedin its protonatedform from waterwith thehelpof otheralkali metalionssuchasK+ or Cs+ by slow evaporation.Thetripleprotonatedsaltcanbeformedby slow aciddiffusion. In thesecompounds,someof theNatomsbelongingto C7N6 ring areprotonatedandthestructuresarestabilizedby extensivehydrogenbonding not only betweenthe [HxC10N12](4-x)- moleculesbut also with watermolecules.Somepreliminaryresultswill bepresentedusingalkali metaleutecticsystemse.g.Li 0.6K0.4Cl andLi 0.5K0.2Cs0.3Cl, to furtherpolymerizethefreeterminalcyanidegroups.Dependingon the reactiontemperature(300-600ºC) a variety of productswere formedwith colors ranging from yellow to orange to red to dark red.

28

The Niobium Oxide Fluoride Anion in the Linear Chain

Heather K. Izumi, Margaret E. Welk, Charlotte L. Stern, Kenneth R. PoeppelmeierNorthwestern University, Evanston, IL 60208-3113

Two new linear chain transition metal oxide fluoride compounds,noncentrosymmetric, chiral Cd(NC5H4NH2)4NbOF5 and centrosymmetricCu(NC5H4NH2)4NbOF5 (NC5H4NH2 = 3–aminopyridine), were synthesized under mildhydrothermal conditions. Previously, the [NbOF5]2- anion in a linear chain motif wascrystallographically disordered as in Cu(N2C5H6)4NbOF5. There is supporting data for anordered [NbOF5]2- anion in Cd(N2C5H6)4NbOF5 owing to an asymmetrical bond networksurrounding the anion that is absent in the Cu containing compound. Both compoundsexhibit extensive hydrogen bonding from the amine groups to the electronegative fluorideligands. Crystal data for Cd(NC5H4NH2)4NbOF5: tetragonal, space group P43 (No. 78),with a = 8.4034(4), c = 34.933(3), and Z = 4; for Cu(N2C5H6)4NbOF5: monoclinic, spacegroup P21/n (No. 14), with a = 8.822(1), b = 16.385(3), c = 8.902(1), β = 109.270(3), andZ = 2.

Synthesis and Characterization of New Materials Featuring 1-D Mixed PnicogenTubular Polymers in the Solid State: Cu2P3-xAsxI2, x � 1.5

Buddhimathie Jayasekera, Jennifer A. Aitken, Mary J. Heeg and Stephanie L. BrockDepartment of Chemistry, Wayne State University, Detroit, MI 48202

The 1-D pnicogen halides (Pnicogen = Group 15 element) are a small class ofrelatively unexplored materials in solid state chemistry: so far limited to Cu-P-X (X = Cl,Br, I). We have begun to look at the potential for producing heavier pnicogen analoguesof these materials, starting with the neutral pnicogen material Cu2P3I2. The structure ofCu2P3I2 features neutral 1-D polymers of phosphorus consisting of fused four- and five-membered rings, surrounded by columns of Cu+ and I-. Cu2P3I2 exhibits moderate copperionic conductivity therefore our specific aim is to test whether the incorporation of aheavier pnicogen, such as As, would decrease the interaction between copper ions and thepnicogen chains, thereby resulting in augmented transport properties. Unfortunately, ourattempts to synthesize a pure As analogue of Cu2P3I2 have not met with success. We have,however, been able to synthesize a series of compounds with mixed pnicogens chains,Cu2P3-xAsxI2, where x � 1.5. These new materials are isostructural to Cu2P3I2 and havebeen characterized by single crystal and powder diffraction techniques. The stabilitiesand physical properties of these phases will be discussed in light of the degree of Asincorporation in the structure.

29

Synthesis and Characterization of New Quaternary Alkali Metal Bismuthchalcogenides:

K1+xAg2-xBi9S15, Rb2Ag3xBi8-xSe13, Rb2CuBi3Se6 and Rb2Cu4-3xBi8+xSe15.

Jun-Ho Kim and Mercouri G. KanatzidisDepartment of Chemistry and Center for Fundamental Materials Research, Michigan

State University, East Lansing, MI 48824

Group15 chalcogenidecompoundshave stimulatedgreatinterestastheyshowpotentialapplications in thermoelectricdevices.The efficiency of a thermoelectricmaterial isdeterminedby the figure of merit ZT = S2σ/κ with the Seebeckcoefficient S, theelectricalconductivity σ, andthe thermalconductivity κ. For exampleBi2Te3, CsBi4Te6

andβ-K2Bi8Se13 showpromisingpropertieswith ZT of ~1, ~0.8and~0.2.Materialswithmore complex compositions and structures may have complex electronic structures whichmay lead to high thermopowerand low lattice thermalconductivity.To do researchonnewmaterialswith complexstructures,thealkali metalchalcogenideflux techniquewasadoptedin compositionallymultiple systems,giving new quaternarycompoundssuchasK1.31Ag1.69Bi9S15, Rb2Ag1.5Bi7.5Se13, Rb2CuBi3Se6 and Rb2Cu3.1Bi8.3Se15. All crystalstructuresare composedof NaCl and Bi2Te3 type building units, which form two- orthree-dimensionalanionicframeworkswith alkali metalionsbetweenthelayersor fillingtunnels.Participationof Ag andCu in well-known mineral bismuthchalcogenidesaltshas provided a variety of new structuresbut not well characterizedyet in theirphysicochemicalproperties.In this researchwith Ag and Cu, the new compoundsobtainedwere examinedwith respectto thermoelectricpropertiesas well as structuresandphysicalproperties.Herewe presentthesynthesis,structure,andcharacterizationofthe aforementioned quaternary bismuth chalcogenide compounds.

High Dielectric Permitivity in the Oxynitride Perovskites BaTaO2N and SrTaO2N

Young-Il Kim and Patrick M. WoodwardDepartment of Chemistry, The Ohio State University, Columbus, Ohio 43210

The syntheses,crystal structuresand optical absorbancespectra of six perovskiteoxynitrides,AMO2N (A = Ba, Sr, Ca; M = Ta, Nb) havebeeninvestigated.Theaveragecrystalstructureof BaTaO2N is a cubic perovskite,with a Ta–O/Ndistanceof 2.056Å,while SrTaO2N and CaTaO2N are distortedby octahedraltilting and show noticeablysmaller Ta–O/N distances,roughly 2.02 Å. Each of the niobium oxynitrides isisostructuralwith its tantalumanalog,thoughthe Nb–O/N distancesareobservedto beslightly longer.Theopticalbandgapsareestimatedfrom diffusereflectancespectrato beas follows: BaTaO2N, 1.8 eV, SrTaO2N, 2.1 eV, CaTaO2N, 2.4 eV, BaNbO2N, 1.8 eV,SrNbO2N, 1.9 eV, andCaNbO2N, 2.1 eV. ComputationalstudieswereperformedusingDFT methodto understandhow the electronegativityof anion,structuraldistortion,andinduction of A cation influence on the electronicstructureof oxynitride compounds.Impedancespectroscopywas carried out on sintered pellets of the ATaO2N andBaNbO2N to investigatethe dielectric and electrical transportproperties.The tantalumcompoundsaresemiconductors/insulatorswith conductivitiesof ~10−5 S/cm(A = Ba, Sr)and ~10−8 S/cm (A = Ca). Interpretationof the impedancedata for BaTaO2N andSrTaO2N reveals that these two compoundshave unexpectedlyhigh bulk dielectricconstants,κ ~ 4900and2900respectivelyat room temperature.Thedielectricconstantsof both compoundsare frequency dependentand show a relatively weak, linear

30

dependenceupon temperaturewith no sign of a phasetransitionover the temperaturerange 300−180 K.

Polar Chains and Interpenetrating Nets; Two Structure Types designed with[Cr2O7]2-.

Amy L. Kopf, Paul A. Maggard, Charlotte L. Stern, Kenneth R. Poeppelmeier;Northwestern University, Evanston, IL 60208-3113

Noncentrosymmetric(NCS) materialsare of interest to the industrial community fornumerousapplicationsbecauseof suchpropertiesaspiezoelectricity,ferroelectricity,andsecondordernon-linearoptical (NLO) behavior.. LiNbO3, a well-known inorganicNLOmaterial,exhibitsan out-of-centerdistortionin the individual [NbO6/2]- octahedra,whichis postulatedto causethe non-linearresponse.Analogousdistortionsarewell known inearly transitionmetaloxide fluoride anionssuchas[NbOF5]2- and[WO2F4]2-. Assymetricmetal oxide anionssuch as [Cr2O7]2- exhibit a net polarizationwhich, when aligned,mimic the electronicpropertiesof distortion in the oxide fluoride anionsand may alsoresult in NLO behavior. Currently, research is being pursued to elucidate thecrystallizationpropertiesof the dichromateanion with late-transitionmetal cationsandamino-groupcontainingligands.Low temperaturehydrothermalmethodologyhaving ahighly acidic environmentcontaininga mineralizeris usedto synthesizethe crystallinematerials.

Synthesis and Characterization of K39In80 with Remarkably Specificand Transferable Cation Dispositions

Bin Li and John D. CorbettAmes Laboratory-DOE and Department of Chemistry, Iowa State University,

Ames, Iowa 50011, USA

The titled compoundK39In80 hasbeensynthesizedby fusion of the elementsinstoichiometricproportion in Nb containers.The trigonal structurewas establishedbysingle-crystalX-ray means(P-3m1,Z = 2, a = b =17.211(2)Å, c = 28.888(6)Å;R1/wR2= 3.1/7.8%).It is a new intermediatebetweenK17In41 and K22In39 compoundswith acomplexstructure.The crystalstructurecanbedescribedasa three-dimensionalindiumnetworkcomposedof five kinds of clusters:threetypeof empty In12 icosahedra,A (12exo-bonds,-3m), B (12 exo-bonds,m), and C (6 exo-bonds,-3m); In17 icosioctahedracenteredby a tetrahedronof In atom (D, 3m); and a ratherdismantledIn15 spacers(E,3m). The measurementsof the electrical resistivity show that the titled compoundismetallic. Remarkablyspecific andtransferablepotassiumdispositionsoccurringaroundeachanionclusterswereobservedin thetitle compoundaswell asin K17In41 andK22In39,which makes it easy to understandtheir structural relationship among these threestructures.All the threestructuresare characterizedby a K136 clathrate-33 network ofalkali metalatoms.Themain differencesamongthemaretheir largerclusterswithin theK28-atomcage.The largercluster[In(In4In12)] inside the K28-atomcageis half or totallysubstitutedby [K(K 4In15)] (In15 spacer)with the increasingof K contentfrom K17In41 toK39In80 andK22In39. The cationson this kind of regularcationpositionscanalsoonly besodium or the mixture of sodium and potassium,as in: (KNa)23In39 (Pnma) and

31

(KNa)22In39 (R-3m). The presenceof the regularcationpositionsis probablydecisiveforthe formation of the whole structures.Acknowledgment:This researchwas supportedby the Office of the Basic EnergySciences,MaterialsSciencesDivision, U.S. Departmentof Energy.AmesLaboratoryisoperated for DOE by Iowa State University under Contract W-7405-Eng-82.

Discovery of New Stable Icosahedral Quasicrystal in Sc-Cu-Zn System

Qisheng Lin and John D. CorbettDepartment of Chemistry and Ames Laboratory, Iowa State University, Ames, IA 50010

Stableicosahedralquasicrystalshavebeenfound as an almostsingle phasein nominalSc15Cu15Zn70 alloy by a quenchand annealprocess.The icosahedralquasicrystalshavethe compositionSc16.2(3)Cu12.3(3)Zn71.5(6), with quasilatticeconstantof 4.9906Ådeterminedby the Elser’s method. An electron diffraction study confirmed that the icosahedralquasicrystalshave a primitive lattice. Triacontahedralsingle grain crystals withdimensionsup to 150 µm havebeengrown by using melt-spinningtechniques.X-raystructurerefinementsrevealthat its crystallineapproximant,Sc3Cu2Zn16, crystallizesin

spacegroup�

3Im , with a = 13.732(2) Å, Z = 8. The local atomicclustercontainsfive

shells: tetrahedron (4) + pentagon dodecahedron(20) + icosahedron (12) +icosidodecahedron(30) + 72-atomssoccerball (72) = 138 atoms.The 3D structureisformedby interpenetratingof the138-atomclustersin bccmanner.Whatinterestedin thestructureis the existenceof tetrahedral,excluding the local five-fold symmetry.Thestructurethereforehelpsto understandhow an internal symmetry-breakingclustercanbuild up to form a bulk quasicrystal.

Synthesis, Structure and Properties of the New Intermetallic Compounds SrPdTl2,SrPtTl2, BaPdTl2 and BaPdTl2

*

Shengfeng Liu and John D. CorbettAmes Laboratory and Department of Chemistry, Iowa State University,

Ames, Iowa 50010

The title compoundshavebeensynthesizedand characterizedstructurallyand throughphysicalpropertymeasurementsand electronicstructurecalculations.Single-crystalX-ray diffraction analysisrevealedthat they crystallizewith the MgCuAl2 structuretype(spacegroup Cmcm,Z=4). Single crystal X-ray datayielded a=4.486(2),b=10.991(5),c=8.154(1) Å for SrPdTl2, a=4.491(3), b=10.990(6), c=8.140(4) Å for SrPtTl2,a=4.5933(3), b=11.2843(5), c=8.2571(9)Å for BaPdTl2, a=4.5454(9), b=11.417(2),c=8.2617(17)Å for BaPtTl2, respectively.Their structuresmaybedescribedaspalladiumor platinum filled versions of the host lattices SrTl2 or BaTl2, respectively. Thecompoundsexhibit a complexthree-dimensionalnetworkbuild of four-bondedthalliumatomsin fuseddistortedhexagonaltunnelsthatbind theSr/Baandtransitionmetalatoms.ThePdor Pt is encapsulatedat thesideof eachtunnelwithin a distortedtrigonal prism.Electronicbandstructurecalculations(EHTB) on SrPdTl2 andBaPdTl2 demonstratetheeffectsof the conversion,with strongPd-Tl andPt-Tl bondingandappreciableelectrontransferfrom Tl to Pd or Pt. Propertymeasurementsshow that SrPdTl2 is metallic, asexpected.

32

*This research was supported by Dept. of Energy, BES, Materials Sciences

Crystal Structure and Property Relationships of Dielectric Perovskites

Michael W. LufasoCeramics Division, NIST, Gaithersburg, MD 20899-8520

Materials with a high dielectric constant, low dielectric loss and near zerotemperaturecoefficient of resonantfrequencyhave potential applicationas dielectricresonatorsat microwavefrequencies.Perovskitesof thegeneralformulaA3MM'2O9 (A =Ba; M = Zn, Mg; M' = Nb, Ta) with a 2:1 ratio of octahedrallycoordinatedM andM'cationshavebeeninvestigatedextensivelyaspromisingmaterialssuitablefor microwavedielectric applications.The relationshipof the crystal structureand chemical factorsinfluencing the dielectric properties are not fully understood. Structure - property relationshipsof 2:1 ordered perovskiteswere investigatedbycomparingcrystal structuresobtainedfrom Rietveld refinementsof X-ray and neutrondiffraction dataandthedielectricproperties.A preliminarybondvalencesumanalysisinrelation to the dielectric properties is presented.Crystal structurespredicted frommodelingarecomparedto thoseobtainedfrom refinementsof experimentaldiffractiondata.

Reduced Cluster Products of Cyanide-Melt Synthesis

Carmela Magliocchi and Timothy HughbanksDepartment of Chemistry, Texas A&M University, College Station, Texas 77842-3012

The tightly cross-linkedMo3nSe3n+2 (n = 2, 3, … )clustersand chain compoundsreactwith alkali metalcyanideor cyanidesalt mixturesat temperaturesof 450-675oC to yieldreduced,cyanide-terminatedmolybdenum chalcogenideclusters. These clusters arethermodynamicallystablespeciesin MCN meltsat specifictemperatures,andarestablein basic aqueoussolutions. We are studying theseelectroactiveclustersas isolatedspeciesandhopeto exploit themasbuilding blocks for materialswith novelproperties.Cyclic voltammetric measurementsperformed on [Mo6Se8(CN)6]n- solutions in basicaqueousmediashowmultiple reversibleredoxwavescorrespondingto [Mo6Se8(CN)6]6-/7-,[Mo6Se8(CN)6]7-/8-, and [Mo6Se8(CN)6]8-/9- couples. Clusters with a cubane core,[Mo4Se4(CN)12]n-, arealso obtainedfrom cyanidemeltsand showmultiple redoxwavescorrespondingto [Mo4Se4(CN)12]6-/7- and [Mo4Se4(CN)12]7-/8- couples. Reductionto givethe anionic cluster compoundNa8[Mo6Se8(CN)6]•20H2O was accomplished.Several[Mo4Se4(CN)12]8- cluster-containingcompoundshave also been synthesizedincludingK7Na[Mo4Se4(CN)12]•5H2O•MeOH andCs7Na4[Mo4Se4(CN)12]Cl3. The processby whichclustersare excisedfrom the CN-linked chain compound,K6Mo6Se8(CN)5 will also bediscussed.

33

Synthesis, Structure and Bonding of Rare-Earth Ternary Chalcogenides

Carmela Magliocchi, Jane Meng, and Timothy Hughbanks*

Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012

Rare earth metal-rich compounds,Gd6MTe2 (M = Co, Ni) and Er6RuTe2, weresynthesizedin direct reactionsbetweenthe R, R3M, andR2Te3 (R = Gd, Er, M = Co, Ni,Ru). Thesematerialsall adoptthesameZr6CoAl2 structuretypewith spacegroup P62m(No. 189,Z = 1). Singlecrystalstructuresof Gd6CoTe2 andEr6RuTe2 weredeterminedandlatticeparametersarea = b = 8.3799(5),c = 3.9801(4)Å, anda = b = 8.1473(5)Å, c= 3.9962(4)Å, respectively. Gd6NiTe2 wascharacterizedby X-ray powderdiffraction;latticeparametersarea = b = 8.412(2),c = 3.9577(9)Å. However,by slightly varyingthesyntheticconditions,an interestingcompetingphase,Gd4NiTe2, was discovered.Thiscompoundcrystallizeswith spacegroupPnma(No. 62, Z =1); lattice parametersarea =15.548(9)Å, b = 4.113(2)Å, and c = 11.752(7)Å.

Toward the Design and Synthesis of Organic Networks

N.J. Melcer, D.T. Vodak, O.M. YaghiUniversity of Michigan, Ann Arbor, Michigan

The rational designand synthesisof extendednetworkscomprisedof covalentinteractionsis an aim lying at the interfaceof organic and solid-statesynthesis.Anoutstandingchallengein chemistryhasbeento obtainsuchmaterialsin crystallineform,which is vital for their propercharacterizationand ultimate utility. Here we report thesynthesisandcrystalstructuresof extendedspiro-orthocarbonate,spiro-phenylacetalandtriazine solids.

Oligospiro-orthocarbonateis synthesizedin one step from pentaerythritolandtetraethylorthocarbonateat 260ºC.A white, insoluble,microcrystallinesolid is obtainedwhosestructureconsistedof hexagonallypackedpentamericchains.Thecrystalstructurewasdeterminedthrougha combinationof electrondiffraction, powderX-ray diffractionand solid-state nuclear magnetic resonance spectroscopy techniques.

This approachhasalsobeenappliedto thereactionof bifunctionalaldehydesandalcohols.An off-white, highly insoluble,crystallinesolid wasobtainedin the solid-statereactionat 200ºC.Its structurewasconfirmedto bethetrans-acetalatedproductthroughacombinationof powderX-ray diffraction, infraredspectroscopy,elementalanalysis,massspectrometry, thermogravimetric analysis, and electron diffraction techniques.Extendedtriazine solids are synthesizedby affecting cyclotrimerizationof polynitrilesandarecharacterizedby singlecrystalX-ray diffraction.Herewe reportthesynthesisandcrystalstructuresof tris-(p-cyanophenyl)-s-triazine,tris-(m-cyanophenyl)-s-triazineandapentamericoligomerof the m-dicyanobenzenemonomersynthesizedfrom a simpleonestep cyclotrimerization reaction.

34

Effects of Texture and Microstructure on Charge Mobility in MOCVD-DerivedCdO Thin Films Grown whith a Thermally Stable, Low-Melting Precursor

Andrew W. Metz, John R. Ireland, Yu Yang, Jun Ni, Charlotte L. Stern, Kenneth R.Poeppelmeier, Carl R. Kannewurf, and Tobin J. Marks*

Department of Chemistry, the Materials Research Center, and the Department ofElectrical and Computer Engineering, Northwestern University, Evanston, IL 60208

A series of low-melting thermally-stable cadmium MOCVD precursors has beensynthesized, structurally/spectrascopically characterized and implemented in the growthof highly conductive and transparent CdO thin films. One member of the series,bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N-Diethyl-N’,N’-Dimethyl-ethylenediamine)cadmium(II), Cd(hfa)2(N,N-DE-N’,N’-DMEDA), represents aparticularly significant improvement over previously described Cd precursors owing toits low melting point and robust thermal stability. High-quality CdO films were grownon Corning 1737F glass and single-crystal MgO (100) between 300°C and 412°C byMOCVD. Processing parameters are shown to have large effects on microstructure,optical, and electrical properties. Both neutral impurity and grain boundary scattering arefound to be important in the present films, even with carrier concentrations that are ashigh as 1.2*1020 cm-3. Conductivities and mobilities as high as 11,000 S/cm and 307(cm2/V•s), respectively, are obtained for epitaxial films (FWHMω = 0.30°, FWHMφ =0.27°) grown in situ on MgO (100) at a relatively low growth temperature (400°C)despite the appreciable lattice mismatch of 8.7%.

POROSITY STUDIES OF METAL-ORGANIC MATERIALS

Andrew R. Millward, Mohamed Eddaoudi, Jaheon Kim, Nathaniel L. Rosi, Andrea C.Sudik, Omar M. Yaghi

University of Michigan, 930 N University, Ann Arbor, MI 4810

Metal-organic frameworks (MOFs) have great potential for applications in gas storage,sensing and catalysis. The porosity of candidate materials is established through gassorption isotherm experiments by measuring the increase in equilibrium mass as afunction of relative pressure. Several extended MOFs and molecular compounds havebeen tested and show porosity as determined from the isotherm data of N2, Ar, CH4, H2,C6H6 and other adsorbate gases. Apparent Langmuir surface areas of up to 4450 m2/ghave been estimated, and pore volumes have been calculated in excess of 1.5 cm3/g.These results illustrate that many of these hybrid metal-organic materials are among themost porous crystalline materials known.

The Crystal and Electronic Structures of Ternary Oxides constructed from edgesharing Sn4+ , Sb5+, or Bi5+ Centered Octahedra.

Hiroshi Mizoguchi, Nattamai S. P. Bhuvanesh, Hank W. Eng, and Patrick M. Woodward,Department of Chemistry, The Ohio State University, Columbus, OH, 43210.

Experimental and computational studies were performed to understand the electronicstructure of rutile (SnO2), trirutiles (ASb2O6, ABi2O6, A = Mg, Zn), ilmenites (ASnO3,A=Ca, Zn, Cd; ASbO3, A=Na, K; ABiO3, A=Na, Ag), and PbSb2O6-type oxides (ASb2O6,

35

A=Ca, Sr, Ba, Cd; ABi2O6, A=Sr, Ba), containing the main group ions: M = Sn4+, Sb5+,and Bi5+. Among these compounds the oxides ABi2O6 (A=Sr, Ba) have been synthesized,for the first time, using a low temperature hydrothermal process beginning from NaBiO3.In all semiconductive compounds which have edge shared octahedral, the lowest energystates in the conduction band arise primarily from the antibonding M 5s(6s) - O 2pinteraction at the Γ point. In SnO2 which is constructed by combination of two rutile-chains running along the c-axis, the conduction band width is dominated by bothinterchain and intrachain Sn 5s-O 2p interactions. The wide conduction band dispersionalong the Γ to Z line originates from the strong orbital interaction along the rutile chain inZ point, due to the symmetry of crystal structure. The conduction band dispersion alongΓ to A line in PbSb2O6-type oxides (A=alkaline-earth ion) is not strong, because of the A-ion’s small electronegativity. These band gaps tend to occur around 5 eV. On the otherhand, in CdSb2O6 the Cd2+ ion exhibits a strong inductive effect that widens theconduction band and lowers the band gap (3.9 eV) significantly. However, theinteraction that gives rise to the conduction band dispersion along the Γ to A line is onlya bonding interaction, therefore, the conduction band dispersion is smaller than observedin SnO2.

Towards Mesoporous Chalcogenide Semiconductors: Sol-gel Chemistry vs.Supramolecular Templating

Jaya L. Mohanan, and Stephanie L. Brock*

Wayne State University, Detroit, MI 48202

Although metal oxide based mesoporous materials have been extensively explored forseveral years, the development of non-oxide mesoporous materials has been relativelyslow. Recently, our group successfully synthesized high surface area aerogels of achalcogenide semiconductor, CdS, for the first time. This was achieved by combiningsol-gel chemistry, using a nanoparticulate precursor, and supercritical fluid drying.Though these aerogels have interesting structural and optical properties, they encompassa wide pore distribution, ranging from the micro-to-macro regime. Currently, we areattempting to prepare mesoporous chalcogenides via supramolecular templating using ananoparticle precursor. In this work, we will compare the above aerogels to templatedmesoporous materials with respect to their morphology, surface area, porosity, andoptical properties. Also, our extension to chalcogenide aerogels other than CdS will bediscussed.

Tracking and understanding first-order structural transition in Er5Si4

Y. Mozharivskyj and G.J. Miller

Ames Laboratory, Iowa State University, Ames, Iowa 50011

Temperature-dependent single crystal X-ray diffraction studies revealed areversible first-order phase transition in Er5Si4. The high-temperature phase adopts anorthorhombic Gd5Si4-type structure with the Si-Si dimers between slabs, and the low-temperature phase has a monoclinic Gd5Si2Ge2-type structure, in which half of the Si-Siinterslab dimers are broken. Unlikely to Gd5Si2Ge2

1 and other related compounds, thestructural change in Er5Si4 is not coupled with magnetic transition and the structural

36

sequence with temperature is opposite. For the first time, we were able to observetemporally and spatially resolved transformation of the monoclinic and orthorhombiclattices, which provides multiple clues to understanding the mechanism of the transitionat the atomic level.

The B1g normal mode, that lowers the symmetry from Pnma to P1121/a, has beenidentified using Landau theory. The mode induces shear movement along the a axis, thusbreaking half of the interslab silicon dimers, and simultaneously rotates slabs, asobserved at the transition point. The orthorhombic-to-monoclinic transformation leads tointrinsic twinning, possibly microscopic, in the monoclinic phase. The distortion follows the conventional Gibbs free energy/entropy relationship:optimization of Er-Si interactions upon the orthorhombic-to-monoclinic transitionminimizes the electronic energy for the low-temperature monoclinic form, but entropycontribution stabilizes the orthorhombic form at high temperatures

1 V. K. Pecharsky, A. O. Pecharsky, and K. A. Gschneidner, J. Alloys Compd. 344, 362(2002).

Fundamental Topologies in Metal-Organic Frameworks

Nathan W. Ockwig, Michael O’Keeffe, and Omar M. Yaghi*

The Materials Design and Discovery Group, Department of Chemistry, University ofMichigan, 930 N. University Ave., Ann Arbor, MI 48109-1055, USA

Metal-organic frameworks (MOFs) are a rapidly advancing class of materials thathave witnessed an explosion of new compounds from a vast variety of metal-ligandcombinations. Despite the tremendous number of new MOF structures reported there arerelatively few detailed analyses of the underlying framework topologies of thesematerials. We have embarked on the systemization of these topologies, methods ofstructure analysis, and finally topology recognition within MOF structures. Theprinciples developed from this study are being used to identify commonly occurring (ordefault) and rare (or non-default) topology types. In addition, these principles can beused to provide chemists with methods of designing crystals with targeted topologies andphysical properties.

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Synthesis, Structure, and Powder Second-Harmonic Generating Properties of NewMixed Metal Oxides

Kang Min Ok and P. Shiv Halasyamani*Department of Chemistry and Center for Materials Chemistry, University of Houston,

136 Fleming Building, Houston, TX 77204-5003

Several new mixed metal oxides have been synthesized by standard solid-state reactions.The structures of the oxides have been investigated by powder and single crystal X-raydiffraction. In addition, the powder second-harmonic generating (SHG) properties of eachmaterial have been measured. The relative SHG efficiencies may be understood byexamining the structure of each material. Through the powder SHG measurements, weestimate the average non-linear optical bond susceptibility, < d2ω

ijk >, as well as determinethe phase-matchability for each material. In addition, structure-property relationships areelucidated.

Novel Polyanionic Arsenic Structures

Ivaylo Petrov and Slavi Sevov

Studied were solutions of various arsenic- and alkali metal-containing solid-stateprecursors in ethylenediamine and 2,2,2-crypt. Thus, an intermetallic with nominalcomposition Na3Cs3Nb2As6 (contains [NbAs4]7-) dissolves readily and forms a dark-redsolution. Red crystals of [Na-(2,2,2-crypt)]Cs5[NbAs8]2 were isolated and characterized.The new compound contaions Nb-centered crown-like As8

8- anions. Similarly, anintermetallic of nominal composition K38Ta7As24 forms a green-red solution whichprovides orange crystals of [K-(2,2,2-crypt)]2As4. This compound contains the novelsquare-like molecules of As4

2- that are isostructural with the known Sb42- and Bi4

2-.

Low Temperature Synthesis of New Lead Oxides and Oxyhalides.

Yetta Porter and P. Shiv HalasyamaniDepartment of Chemistry and Center for Materials Chemistry, University of Houston,

136 Fleming Building, Houston, TX 77204-5003

Nonlinear optic materials have optical properties that can be modified by light asit passes through the material. These materials have many applications in devices such astunable parametric oscillators and frequency doublers. All nonlinear optic materialscrystallize in noncentrosymmetric space groups. This symmetry requirement is evidentin 21 of the 32 space groups; of these 21, twenty exhibits second harmonic generation(SHG). This nonlinear optic property doubles the frequency of laser radiation. There ismuch interest in finding materials exhibiting SHG efficiently. Our group has devised atheory to synthesize new mixed metal oxidic compounds utilizing cations which undergosecond-order Jahn-Teller distortions. These electronic distortions cause acentricenvironments about the cations, therefore, creating units with net polarizations. Thisasymmetry is not a sufficient condition to produce crystallographic noncentrosymmetry.The units must align in an antiparallel manner to form a macroscopically

38

noncentrosymmetric material. Once the material is formed, second harmonic generationmeasurements were conducted on a modified powder Kurtz-NLO system using 1064 nmradiation, with the intensities compared to the reference material, quartz. An analysis ofthe structure is used to explain the origins of the SHG. There has been considerableresearch conducted to find alternatives to the conventional solid-state method ofsynthesizing new mixed metal oxides and oxyhalides. In this case, a low temperature,aqueous, reflux system was used to form new lead oxides and oxyhalides. This methodlead to facile synthesis and high yields. We report three new structure types with onecrystallizing in a noncentrosymmetric (NCS) group. Second harmonic generationmeasurements were conducted on the NCS compound.

Rapid Acquisition Pair Distribution Function (RA-PDF) Analysis: a Local StrctureProbe

Xiangyun Qiu and Simon J.L. BillingeDepartment of Physics and Astronomy, Michigan State University, E. Lansing, MI 48824

Peter J. Chupas and Clare P. GreyDepartment of Chemistry, State University of New York at Stony Brook, Stony Brook,

NY 11794Jonathan C. Hanson

Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11973Peter L. Lee

Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439

Atomic pair distribution function (PDF) technique has proved to be a powerful tool tostudy the local structure of structurally complex materials. However, the long datacollection time (8 hours) required by conventional PDF experiments is a key limitingfactor to its wider application. Here we present that, high-energy synchrotron radiationcoupled with an area detector (image plate) can reduce measuring time to seconds orminutes, with momentum transfer Qmax ≤ 28.5 A-1. Crystalline materials with differentstructural complexities (Ni, AlF3, and the layered Aurivillius type oxides α-Bi4V2O11 andγ-Bi4V1.7Ti0.3O10.85) were measured to test the validity of this quantitative PDF dataanalysis. All experimental PDFs are of high quality and highly reproducible whensamples are similar. The new combination of real space probe and fast counting timeopens up a broad field for future application to wide varieties of materials of bothscientific and technological interest. Structural changes under in-situ conditions and timedevelopment of chemical reactions and biological systems can also be studied.

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Using Theory to Find High Spin Rare Earth Clusters

Lindsay E. Roy and Timothy HughbanksDepartment of Chemistry, Texas A&M University, College Station, TX 77843-3012

Open-4f-shell rare-earth elements provide one of the richest regions for interesting anduseful magnetic and conducting properties. However, efforts are needed to advance ourunderstanding of the key factors controlling magnetic properties in order to guide rationalexperimental development of this field. Our goal is to provide a basis of correlatingstructure, bonding, and magnetic properties of rare-earth molecular compounds withmore specific applicability in a manner analogous to the Goodenough rules, or the Hay-Thibeault-Hoffmann and Kahn-Briat models. We have developed a semi-quantitativeanalysis of d-electron mediated f-f exchange in rare-earth metal-rich cluster compoundsto construct and check features of a generally applicable qualitative approach tounderstanding their magnetic coupling. Results from benchmark systems includeinvestigations of indirect 4f7-4f7 coupling in cluster and condensed-cluster gadoliniummaterials. Spin density functional theory (SDFT) molecular orbital and band structurecalculations were performed and we show that open-d-shell clusters facilitate strongferromagnetic coupling whereas closed-d-shell systems prefer antiferromagneticcoupling. This method has been successful evaluating the ground state for model clustersystems based on GdI2, Gd[Gd6FeI12], and condensed cluster system, Gd2Cl3. A detaileddiscussion of Gd[Gd6FeI12] will be presented, using a perturbative molecular orbital(PMO) model that focuses on the influence of the 4f7-d exchange interaction on the d-based molecular orbitals. Extension of our analysis to prospective magnetic clusters isunderway involving Gd5O(OPri)13, whose relatively short Gd-Gd contacts and the cationicnature of the cluster core, [Gd5(µ5-O)(µ3- OPri)4(µ-OPri)4]5+, suggest that this cluster maybe reduced and f-f exchange coupling could be enhanced through metal-metal bonding.

A DFT Study on the Interstitial Chemical Shifts of Main Group Element CenteredHexazirconium Halide Clusters

Jingyi Shen and Timothy HughbanksDepartment of Chemistry, Texas A&M University, College Station, TX 77843-3012

NMR spectra of the interstitial atoms in the zirconium halide clusters have been veryuseful in understanding the chemistry of these clusters in both solids and solution.Compared with ordinary diamagnetic molecules, these interstitial nuclei are highlydeshielded. Trends have been observed as the bridging halides progress from Cl to I. Aqualitative DFT study based on Ramsey’s equation has been carried out aiming toestablish the correlation between the trend of interstitial chemical shifts and the change inelectronic structure. The influence of halide variation on electronic structure was studiedwith two series of model compounds [(Zr6Z)X12](H2O)6

n+ (Z=B, C, X=Cl, Br, I). Theeffect of terminal ligands on overall electronic structures was also studied with modelcompounds [(Zr6B)Cl12]L6

n+, where L= H2O, PH3, HCN and OPH3. Inverseproportionality has been found between the chemical shifts and the calculated energygaps ∆E(t1u- t1u*) for each series of compounds, where t1u and t1u* orbitals are the bondingand antibonding orbitals resulted from the interaction between the zirconium cagebonding orbitals and the interstitial 2p orbitals. We conclude that the deshielding of theinterstitial atoms is mainly attributable to the paramagnetic contribution which arisesfrom the second order mixing involving the t1u and t1u* orbitals in the applied magnetic

40

field. A quantitativestudyon the nuclearmagneticresonanceshieldingtensorsfor the[(Zr6B)X12](H2O)6n+ (X=Cl, Br, I) series has also been performed with DFT/GIAOmethod.

Synthesis, structure, and thermoelectric properties of AδMo3Sb5Te2

N. Soheilnia, H. KleinkeUniversity of Waterloo, Department of Chemistry, Waterloo, ON, Canada N2L 3G1

Thermoelectricmaterialsmay eitherconvertheat(moreprecisely,a temperaturegradient) into electricity or vice versa.The materialscommercially used are usuallynarrow gap semiconductorscomprising heavy elements.Several new materials arecurrently under investigationbecauseof their promising thermoelectricproperties,inparticular;the telluride CsBi4Te6 andthe antimonideLnδM4Sb12 with 0 ≤ δ ≤ 1, with Lnbeinga lanthanoidandM a late transitionelementsuchasFe,Co, Ni, … LaFe3CoSb12

exhibits outstandingthermoelectricproperties,for its good thermopowerand electricalconductivityare combinedwith an extraordinarilylow thermalconductivity.The latterstemsfrom the high vibrationsof the La atomsituatedin a large"cage"of Sb atoms,aphenomenon usually referred to as rattling.

We recently succeededin modifying Mo3Sb7 to obtain the semiconductingantimonide-tellurideMo3Sb5Te2, which comprisesa calculatedbandgapof 0.45eV. Ournextstepsto renderthis materialmoreusefulinvolve incorporationof small cationsintoan Sb8 cubeof this structure:this void may get filled to, e.g.,14 % with Mg atomsasconfirmedvia singlecrystalstructurestudies.This contributiondescribesthesynthesesofAδMo3Sb7 andAδMo3Sb5Te2 with A = Mg, Ni, and Cu. Adding Mg cationsleadsto anincreaseof valence-electronsas well as a decreaseof the band gap. However,as 55valence-electronsper formula unit are neededto fill all statesbelow the gap, the filledMg-containingmaterialhasan ideal formula of "MgδMo3Sb5+2δTe2-2δ". Physicalpropertymeasurements confirm the prediction that these materials are semiconducting.

Synthesis and Characterization of Nanoscale Transition Metal PhosphidesProduced via Precursor Reduction

Kimber L. Stamm, Stephanie L. BrockWayne State University, Detroit, MI 48202

Bulk transitionmetalphosphidesexhibit interestingmagneticandelectronicproperties,yet there are few reports of exploring these materials and their propertieson thenanoscale.Our lab hasdevelopeda synthesisbasedon reductionof nanoscalephosphateprecursorsunder flowing H2/Ar to yield various phasesof dimensionally limitedphosphides. In order to avoid sintering, the nanoparticleprecursorsmust first bedispersedonto substratesurfacesprior to annealing. This method has successfullyproduced nanoparticles of FeP and Fe2P on mica.Another way to limit the degreeof sintering is by using a template with orderednanoscalepores. We are investigatingthe suitability of porous alumina membranes(Anodisc,Whatman)for the productionof wire-like morphologies.Thesematerialswillbe limited to nanoscaledimensionsin only two directionsandarethereforeexpectedto

41

have orientation dependant properties. Our synthetic efforts to produce crystallinenanowires of iron phosphides (FeP and Fe2P) will be discussed and these materials willbe compared to the 3-D limited nanoparticles produced by sintering on mica.

Discrete and Extended Metal-Organic Frameworks of Iron

Andrea C. Sudik, Jaheon Kim, Omar M. YaghiMaterials Design and Discovery Group, Department of Chemistry, University of

Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055

Although the majority of metal-organic frameworks contain transition metals, relativelyfew have been reported with iron, an avenue which could lead us to target biologicallyrelevant structures. More specifically, the redox activity, enzymatic activity and electron-transfer properties inherent to iron, make it an attractive metal for inclusion. Efforts toincorporate iron into extended arrays have afforded a series of ferrous, ferric, and mixed-valent, infinite two- and three-dimensional frameworks, some of which containmagnetically or electronically interesting building units, such as the oxo-centered [Fe3O(ROOC)3L3]+/0 trimer or the [Fe2(ROOC)2L2] paddle-wheel dimer. Conditions have alsobeen discovered to isolate a two-dimensional framework composed of dimeric iron-carboxylate clusters which structurally resemble those found in the active site of methanemonooxygenase, a bacterial enzyme which catalyzes the conversion of methane tomethanol. The above approach for preparation of extended solids using metal-carboxylate buildingblocks can also be translated to molecular chemistry, serving as a viable route forgeneration of porous, finite species. Modification of the above synthesis using a lesslabile iron counterion has resulted in the isolation of an anionic truncated tetrahedron,[Fe12O4(p-C14H8O4)6(SO4)12(pyr)12]8- (A), composed of sulfate capped triiron units with p-biphenyldicarboxylate serving as the link. Preliminary sorption data suggests thesemolecules are indeed porous, adsorbing a variety of inert gases and organic vapors, withapproximate surface area, 494 m2/g. Understanding the synthetic parameters under whichthe vertex clusters in (A) form, we have been able to introduce both linear and branchedorganic di- and tri-carboxylate linkers to produce the overall same truncated tetrahedronpolyhedron (B). Upon discovery of (A), it was thought that analogous discrete sulfateterminated supramolecules could also be obtained in the presence of other carboxylic acidlinkers. These ongoing investigations also include the synthesis and characterization of afinite triangle whose vertices are composed of polyoxo-hexairon clusters.

[Fe12O4(p-C14H8O4)6(SO4)12(pyr)12] [H2N(CH3)2]8 [Fe12O4(p-C27H18O6)4)(SO4)12(pyr)12][H2N(CH3)2]8

(A) (B)

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Synthesis of Transition-Metal Phosphides by Direct Reduction of their Phosphates

Christina M. Sweeney, Kimber L. Stamm, and Stephanie L. BrockDepartment of Chemistry, Wayne State University, Detroit, MI 48202

Phosphates of a number of metals, including Mo, W, Fe, Ni, and Ru, are known to reduceto single-phase phosphides upon reductive annealing. It has been suggested that theprediction of which metal phosphates will successfully produce phosphides is directlyrelated to redox properties of the metal. Metals whose oxides will not reduce to themetallic state, such as Mn and Ga, also will not undergo reduction from phosphate tophosphide. However, based on this premise, several additional late metal phosphatesmay be capable of reduction to phosphide. We are testing this hypothesis for the metalsAg, Rh, Ir, and Re. Our attempts to prepare crystalline phosphate precursors by solutionprecipitation, and the results of our subsequent reductive annealing, will be discussed.

Investigation of Metal Clusters as Molecular Precursors for Transition MetalPnictide Nanoparticle Synthesis

Kristy Symons†, Arvind Kumar‡, Kenton H. Whitmire‡, Stephanie L. Brock†

†Department of Chemistry, Wayne State University‡Department of Chemistry, Rice University

The focus of our research is to synthesize transition metal pnictide (pnicogen = Group 15element) nanoparticles from single source precursors. Transition metal pnictidesconstitute an important area of study due to their intriguing magnetic properties;however, controlling stoichiometry in these materials remains a challenge. The use ofmolecular, or single source precursors should provide control of the stoichiometry of theresulting nanoparticles. We are interested in identifying appropriate precursors for ourtargeted phases, and using these for the synthesis of nanoparticles through thermaldecomposition in coordinating solvents. The clusters Mn(CO)5BiPh2 and {Mn(CO)}3Biare currently under investigation as precursors for the synthesis of manganese bismuthidenanoparticles. The thermal degradation of the metal clusters in solution and in the solidstate will be discussed.

Aromaticity in Sn- and Pb- based Zintl Phases.

Iliya Todorov and Slavi Sevov*

Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame,Indiana 46556

Although aromaticity has been extensively studied for more than a century, thereis still no generally acceptable definition. This concept was invented to account for theunusual stability of certain organic molecules: the aromatic compounds. The mostsignificant feature that they exhibit is a planar structure with a delocalized system of(4n+2) -electrons.The most general point of view on aromaticity combines geometry(bond length equality), energy (aromatic stabilization energy) and magnetism(diamagnetic susceptibility exaltations). However this property has never beeninvestigated carefully and systematically in all-metal species. Here we report thediscovery of three isostructural Zintl phases with aromatic anionic pentagonal rings madeof Sn and Pb, Sn5

6- and Pb56-. Furthermore two other phases having anionic pentagonal

43

rings have been discovered in a detailed study of the Li-Eu-Sn system. All compoundshave been synthesized by direct fusion of the elements at 800° C and characterized bysingle crystal X-ray diffraction. These are the first heavy main-group species with anaromatic ring. It is very unusual that such heavy atoms can form aromatic structures.

Reactions of nine-atoms germanium clusters in solution

Angel Ugrinov and Slavi SevovDepartment of Chemistry and Biochemistry, University of Notre Dame, Notre Dame IN

Interest in synthesis, isolation and characterization of delthahedral Zintl ions fromsolutions dates back to the 19th century. Numerous attempts to use these species invarious reactions have been made, some successful and some not. It has been shown, forthe first time in our group, that “normal” 2-center-2-electron bonds can form betweensuch clusters with delocalized bonding, Ge9

4- for example. Based on the existence of thedimers of [Ge9-Ge9]6-, and the chain of [-(Ge9)2--]∞, it is only natural to look also foroligomers of various sites.The poster presents some of the results of our investigation of reactions with thegermanium nine-atom clusters in solution. We show that it is possible to attach group 15or group 14 substituents to such clusters. Ethylenediamine solutions of the precursorA4Ge9 (A=K or Rb) react with SbPh3, BiPh3 or SnPh4 and give yield [Ph2SbGe9SbPh2]2-

(same for Bi), [Ph2SbGe9Ge9SbPh2]4-, [PhGe9SbPh2]2-, [Ph3SnGe9SnPh3]2- and [Ge9SnPh3]3-

. The same reactions with AsPh3 and PPh3 provide linear trimer of germanium clusters,[Ge9=Ge9=Ge9]6-. Later we found that the trimer can be just using high concentration ofprecursor in en and appropriate cation sequestering agent. Following the same idea butchanging the cation sequestering agent we obtained a tetramer, [Ge9=Ge9=Ge9=Ge9]8-.

Aqueous Tetraperoxo Cr(V) will not Reduce Directly to Cr(III) Hydroxide

Douglas A. Vander GriendDepartment of Chemistry & Biochemistry, Calvin College

3201 Burton Street SE, Grand Rapids, MI 49546

Joshua S. Golden and Charles A. Arrington Jr.Department of Chemistry, Furman University

3300 Poinsett Highway, Greenville, SC 29613-1120

The reaction of chromium with hydrogen peroxide in basic media hinges on thechemistry of tetraperoxo chromium(V). Several intermediates, including a triperoxospecies, can be identified kinetically in the reaction that produces Cr(O2)4

-3 from CrO42-.

More stable in base that peroxide itself, Cr(O2)4-3 can then convert to only a

chromium(VI) species, even under reducing conditions which ultimately generatechromium(III). Both the one electron reduction of chromium(VI) and the complementaryoxidation of chromium(V) likely produce superoxide, which may play a key role in thetoxicity of high-valent chromium.

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Synthesis and Characterization of New Intermetallic Tetrelides Using Al as a Flux

Xiuni Wu and Mercouri G. Kanatzidis*Department of Chemistry and Center for Fundamental Materials Research, Michigan

State University, East Lansing, MI 48824

Metal silicides and germanideshavereceivedwide applicationsas advancedstructuralmaterialsand electronic device materials. Conventionalmethodsto synthesizethesematerials rely on direct combination of elemental reactantsat high temperatures,normallyover1500°C, andpowdersamplesareusuallyobtainedfrom suchmethods.Theuseof metalfluxespresentstheadvantagessuchaslower reactiontemperatures,facilitatethe growth of single crystals,etc. In our group, the applicationof Al as the flux tosynthesizenew multinary intermetalliccompoundscontaininga rareearthmetal,first orsecondrow late transitionmetal,aluminum,andsilicon or germaniumhasshowngreatsuccess.Recently,we have beenexploring the systemcontainingthird row transitionmetalsinsteadof first or secondrow transitionmetals.Gold wasfirst selectedbecauseofits noble metal statusand unusualelectronegativity.In the Au-containingsystem,twoanalogswereobtained:REAuAl4Ge2 (RE = Ce,Pr,Nd, Sm,Eu,Gd,Tb, Dy, Er, Tm, Yb)andREAuAl4(AuxGe1-x)2 (RE= Ce,Eu).At thesametime,we startedextendingour studyof synthesizingintermetallic tetrelidesto a new systemT1/T2/Al/Si(Ge) (T1 and T2 aretransitionmetals)using Al as the high temperaturesolvent.From this system,ternarycompoundsarereadilyformed. Co19Al 42Si13-x (x = 0.2)andV2Al 5Ge5 aretwo newternaryphasesformedfrom this systempresentinginterestingstructures.All thematerialshavebeen structurally characterizedby energy dispersivespectroscopy(EDS) and X-raydiffraction analysis. Magnetic susceptibility measurements have also been conducted.

Investigation of Niobium oxychloride cluster compounds: Synthesis and crystalstructure of the composite layered compound Nb10Cl16O7

Yan Zhihua, Abdou LachgarDepartment of Chemistry, Wake Forest University, Winston-Salem, NC 27109

Our investigationof niobium oxychloridescontainingoctahedralNb6 clustersled to thediscoveryof the oxychlorideNb10Cl16O7. The compoundwas obtainedfrom solid-statereactionof a mixtureof NbCl5, Nb2O5 andNb powderin a sealedsilica tubeat 820°C.Itscrystal structurewas determinedby single crystal X-ray diffraction techniques(spacegroup I 2/m, a = 12.876(1)Å, b = 3.2580(3)Å, c = 15.529(1)Å, = 103.92(1)°,V =632.37(10) Å3, Z = 4). The framework Nb10Cl16O7 is based on (NbClO)Cl clusterunits thatsharetwo inneroxygenandfour outerchlorine ligandslocated in the equatorial plane to form a cluster chain with connectivity formula(NbCl6iO4

iO)Cl Cl. The cluster chain is linked to a double chain formed of NbCl4O2

octahedrasharing chlorine edges and oxygen vertices. The double chains connectneighboringclusterchainsby sharingtwo outerchlorineandfour inneroxygenligandsofthe cluster to form a two-dimensional framework.

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Hydrothermal synthesis and crystal structure of hybrid metal phosphate-oxalates:[Mn2(H2PO4)4(C2O4)2](C10N4H28) 5H2O and [In6(PO4)8(C2O4)3](C10N4H28)3

Yue Zhao, Yumi Okuyama, Abdou LachgarDepartment of Chemistry, Wake Forest University, Winston-Salem, NC 27109

Two novel framework materials in the metal-phosphate-oxalatesystem have beenpreparedby hydrothermal reaction carried out in Teflon-lined stainlesssteel Parrautoclaveat 150 °C for 3 days using 1,4-Bis(3-aminopropyl)piperazineas structure-directing agents (SDA). The compound [Mn2(H2PO4)4(C2O4)2](C10N4H28) 5H2O ( )crystallizesin thetriclinic system,spacegroupP-1(No. 2), a=10.1087(9)Å, b=11.342(1)Å, c=16.751(2)Å, =80.79(1)°, =77.13(1)°, =86.945(5)°, V=1848(5)Å3, Z=2. (I) hasa 1D frameworkformedof vertex-sharingMnO6 andH2PO4 polyhedralinked by bridgingoxalateligandsto form hybrid chainsrunningalonga axis.Thechainsareseparatedfromeachotherby theSDA moleculesandinteractthroughhydrogenbonding.Thecompound[In6(PO4)8(C2O4)3](C10N4H28)3( )crystallizesin the trigonal system,spacegroup P-3c1(No. 165), a=14.004(2)Å, c=15.191(3)Å, V=2580.0(7)Å3, Z=2. Its 3D framework isformed of InO6 octahedra and PO4 tetrahedra sharing corners to form inorganic rods alongc axis. The rods are linked via oxalate ligands to generatelarge channelsin whichdisordered SDA cations are located.

1D framework of ( ) 3D framework of ( )

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Cluster chain

Double chain

One-Dimensional coordination polymer based on octahedral [Nb6Cl12(CN)6]4- clusterunits and [Mn(III)(salen)]+ metal complex as building blocks

Huajun Zhou and Abdou LachgarDepartment of Chemistry, Wake Forest University, Winston-Salem, NC 27109

A novel one-dimensionalframeworkbasedon octahedralniobium cyanohalidecluster,[Nb6Cl12(CN)6][Mn(salen)(MeOH)]2[Et4N]2. 2MeOH (salen = N,N-ethylenebis(salicylideneaminato))was preparedby reaction of aqueoussolution of[Et4N]4[Nb6Cl12(CN)6] with a solution of the complex [Mn(salen)]ClO4 in methanol at RT.The compound was characterizedby single-crystal X-ray diffraction and IR. Thecompoundcrystallizesin themonoclinicsystem,spacegroupP 21/c, a = 13.227(1) Å, b =21.800(2)Å, c = 13.781(1)Å and = 93.648(6)°,Z = 2. The framework is built of[Nb6Cl12(CN)6]4- cluster units that sharetwo trans apical cyanideligands with Mn (

�)

leading to the formation of trimeric units [Mn-(NC)[Nb6Cl12(CN)4](CN)Mn]. EachMn(III) is trans-coordinatedby onecyanideligandfrom theclusterandonemethanol,inaddition to the salenligand. The trimers areconnectedto eachother throughhydrogenbonding to form anionic chains along the crystallographic a axis{[(Nb 6Cl12)(CN)6][Mn(

�)(salen)(MeOH)]2} 2-. Hydrogen bonding O – H ---N forms

betweenthe methanolligandson manganeseandcyanideligandsfrom two neighboringclusters. A c-glide plane relates adjacent chains to each other.

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i a) Derstroff, V.; Ksenofontov, V.; Gûtlich, P.; Tremel, W. Chem. Commun. 1998, 2, 187-188. b) Coste,S.; Kopnin, E.; Evain, M.; Jobic, S.; Payen, C.; Brec, R. J. Solid State Chem. 2001, 162, 195-203. c) Coste,S.; Kopnin, E.; Evain, M.; Jobic, S.; Brec, R.; Chondroudis, K.; Kanatzidis, M. G. Solid State Sci. 2002, 4,709-716. d) Kopnin, E.; Coste, S.; Jobic, S.; Evain, M.; Brec, R. Mat. Res. Bull. 2000, 35, 1401-1410.ii Tarascon, J.M.; Hull, G.W.; Disalvo, F.J. Mat. Res. Bull. 1984, 19, 915-924.iii Elder, S.H.; Van der Lee, A.; Brec, R.; Canadell E. J. Solid State Chem. 1995, 116, 107-112.iv a) Chondroudis, K.; Kanatzidis, M. G.; Sayettat, J.; Jobic, S.; Brec, R. Inorg. Chem. 1997, 36, 5859-5868. b) Coste, S.; Hanko, J.; Bujoli-Doeuff, M.; Louarn, G.; Evain, M.; Brec, R.; Alonso, B.; Jobic, S.;Kanatzidis, M. G. J. Solid State Chem., accepted (2003).v a) Sayettat, J.; Bull, L.M.; Jobic, S.; Gabriel, J.C.P.; Fourmigué, M.; Batail, P.; Brec, R.; Inglebert, R.-L.;Sourisseau, C. J. Mater. Chem. 1999, 9, 143-153. b) Sayettat, J.; Bull, L.M.; Gabriel, J.C.; Jobic S.;Camerel, F.; Marie, A.-M.; Fourmigué, M.; Batail, P.; Brec, R.; Inglebert, R.-L. Angew. Chem. Int. Ed.1998, 37, 1711-1714.vi a) Tarascon, J.M.; Disalvo, F.J.; Chen, C.H.; Carroll, P.J.; Walsh, M.; Rupp, L. J. Solid State Chem.1985, 58, 290-300. b) Davidson, P.; Gabriel, J.C.P.; Levelut, A.M.; Batail, P. Europhysics letters 1993, 21,317-322.vii Coste, S.; Gautier, E.; Evain, M.; Bujoli-Doeuff, M.; Brec, R.; Jobic S. and Kanatzidis, M.G. Chem.Mater., accepted 2003.

Yb2Ga4Ge6 and Yb3Ga4Ge6: Novel Zintl Phases Grown From Molten Ga. X-rayStructure Determination, Electronic Structure Calculations and Physical Properties

Marina A. Zhuravleva(a), James Salvador(a), Daniel Bilc(b), S. D. Mahanti(b), John Ireland(c),Carl R. Kannewurf(c), and Mercouri G. Kanatzidis(a)

(a)Department of Chemistry, Michigan State University, E. Lansing, MI 48824(b)Department of Physics and Astronomy, Michigan State University, E. Lansing, MI

48824(c)Department of Electrical Engineering and Computer Science, Northwestern University,

Evanston, IL 60208

Two new intermetallic compounds,Yb2Ga4Ge6, Yb3Ga4Ge6, were obtained from thereactionsin molten Ga. The crystal structuresof thesecompoundswere studiedwithsinglecrystalX-ray diffraction. The Yb2Ga4Ge6 crystallizesin an orthorhombiccell a =4.1698(7)Å, b = 23.254(4)Å, c = 10.7299(18)Å, Z = 4 in a polar spacegroupCmc21.Thestructureof Yb3Ga4Ge6 is monoclinic,spacegroupC2/m, Z = 4, cell parametersa =23.941(6)Å, b = 4.1928(11)Å, c = 10.918(3)Å, β = 91.426(4)°.Thestructuresof thesetwo families of compoundscanbedescribedusinga Zintl conceptof bonding,in whichthe three-dimensional[Ga4Ge6]n- frameworkservesasa hostandan electronsink to theelectropositiveYb atoms.Eventhoughthe idealZintl ion formulationcouldbegiven fortheanionic [Ga4Ge6] network,thesecompoundsaremetallic conductors.The relationofcrystal structureof Yb3Ga4Ge6 to that of Yb2Ga4Ge6 lies in a monoclinic distortion oforthorhombic cell of Yb2Ga4Ge6 and a reduction of the [Ga4Ge6] network by two electronsper formulaunit. The resultsof the theoreticalelectronicstructurecalculations,transportdata and magnetic measurements are also reported.