Found 16 Abstracts CONTROL ID: 1688992TITLE: How do environmental perturbations affect the reactivity of metal(IV)-oxo species?AUTHORS/INSTITUTIONS: S. de Visser, Manchester Institute of Biotechnology, University of Manchester,Manchester, UNITED KINGDOM|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: High-valent metal-oxo species are common intermediates in enzymatic processes and have beenidentified in heme as well as nonheme iron enzymes, where often the catalytic intermediate is an iron(IV)-oxo species[1]. We have performed a series of density functional theory calculations (DFT) to establish the properties of theoxidant that determine the reactivity patterns and make it a more efficient catalyst. Thus, we investigated the effect ofligands on the reaction patterns, including the axial and equatorial ligand effect and showed that the BDE(OH) valueand consequently the reactivity is ligand dependent. In addition, we studied the effect of hydrogen bonding donation tothe iron(IV)-oxo center as well as the interaction of a cation to the iron(IV)-oxo species [2,3]. These studies show thatseemingly minor perturbations to the oxidant through weak/non-covalent interactions may result in major catalyticdifferences due to their electrostatic effects on orbital occupation. As a result these interactions can affect theoxidative properties in a positive or negative way. We have analyzed these perturbations and come with models thatexplain the reaction patterns. 1. de Visser, S. P.; Kumar, D. (Eds.) Iron-containing enzymes: Versatile catalysts of hydroxylation reactions in nature;Royal Society Publishing, Cambridge (UK), 2011.2. Leeladee, P.; Baglia, R. A.; Prokop, K. A.; Latifi, R.; de Visser S. P.; Goldberg, D. P. J. Am. Chem. Soc. 2012, 134,10397–10400.3.Latifi, R.; Sainna, M. A.; Rybak-Akimova E. V.; de Visser, S. P. Chem. Eur. J. 2013, in press.

CONTROL ID: 1711153TITLE: Controlling Molecular Catalysts with a Peptide-Based Outer Coordination SphereAUTHORS/INSTITUTIONS: W. Shaw, M. Reback, B. Ginovska-Pangovska, J. Roberts, S. Raugei, Pacific NorthwestNational Labs, Richland, Washington, UNITED STATES|A. Jain, Indiana University of Pennsylvania, Indiana,Pennsylvania, UNITED STATES|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: This work focuses on using peptides to introduce enzyme-like features into molecular catalysts. Theouter coordination sphere (OCS) of enzymes consists of the regions controlling reactivity, but not directly attached tothe metal. Features such as dynamics, the active site environment and proton channels are some of the features ofthe outer coordination sphere (OCS) that are the focus of these studies. We are developing redox active catalystswhich oxidize and produce hydrogen, mimicking the hydrogenase enzyme. Like other enzymes, hydrogenaseenzymes use many OCS features to very efficiently convert H+ to hydrogen and back again. Our initial work in thisarea has focused on incorporating small peptides around the active site of the Ni(P2RN2R’)2 hydrogenproduction/oxidation catalysts to explore how the local environment can influence catalytic rates. We have found thatthe addition of small peptides with a variety of functional groups including polar, acidic and basic groups, modulatesthe activity of the parent catalyst by an order of magnitude and influences the overpotential at which the catalystoperates, demonstrating that regions remote from the active site do modulate this activity. We are currentlyinvestigating the role of adding a larger peptide to introduce the structural stability of the enzyme, to more preciselycontrol and direct the features of the outer-coordination sphere.

Peptide-based hydrogenation,hydrogen production and hydrogen oxidation catalysts.

CONTROL ID: 1714114TITLE: Synthesis, Characterization, and Reactivity of Hypochlorito-Iron(III) Porphyrin ComplexesAUTHORS/INSTITUTIONS: H. Fujii, Z. Cong, T. Kurahashi, Institute for Molecular Science, Okazaki, JAPAN|S.Yanagisawa, T. Ogura, University of Hyogo, Ako, JAPAN|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: Myeloperoxidase (MPO) and chloroperoxidase (CPO) are unique heme peroxidases that catalyzeoxidation of chloride ion to hypochlorite ion (OCl–). MPO is loctaed in azurophil granules of neutrophils and producesOCl– or hypochlorous acid (HOCl), which works as an antimicrobial agent, from hydrogen peroxide and chloride ion.On the other hand, CPO is an enzyme of Caldariomyces fumago and catalyzes chlorination reactions in thebiosynthesis of the chlorinated metabolite caldariomycin. It has been proposed that ferric MPO and CPO initially reactwith hydrogen peroxide to form an oxoiron(IV) porphyrin π-cation radical species known as compound I. Compound Ithen reacts with chloride ion to form a transient hypochlorito-iron(III) porphyrin intermediate, which finally releasesHOCl with the protonation of the heme-bound hypochlorite. In addition, hypochlorito-metal complexes have beenproposed as key intermediates in catalytic oxygenation reactions catalyzed by transition-metal complexes. We reportherein the preparation, spectroscopic characterization, and reactivity of hypochlorito-iron(III) porphyrin complexes, abis-hypochlorite complex, [(TPFP)FeIII(OCl)2]– (1), and imidazole-hypochlorite complexes, (TPFP)FeIII(OCl)(1-R-Im),where TPFP is 5,10,15,20-tetrakis-(pentafluorophenyl)porphyrinate and R is –CH3 (2), –H (3), or –CH2CO2H (4). Thestructures of 1 ~ 4 are confirmed by absorption, NMR (2H and 19F), EPR, resonance Raman spectroscopy, and ESI-MS spectrometry at low temperature. The reactions of 1 and 2 with various organic substrates show that 1 and 2 arecapable of chlorination, sulfoxidation, and epoxidation reactions, and that 1 is much more reactive with thesesubstrates than 2. References[1] Z. Cong, S. Yanagisawa, T. Kurahashi, T. Ogura, S. Nakashima, H. Fujii, J. Am. Chem. Soc., 2012, 134, 20617[2] Z. Cong, T. Kurahashi, H. Fujii, J. Am. Chem. Soc., 2012, 134, 4469[3] Z. Cong, T. Kurahashi, H. Fujii, Angew. Chemie. Int. Ed., 2011, 50, 9935(No Image Selected)

CONTROL ID: 1714553TITLE: Towards computer aided design of artificial metalloenzymesAUTHORS/INSTITUTIONS: J. Maréchal, V. Muñoz-Robles, P. Vidossich, A. Lledós, Química, Universitat Autònomade Barcelona, Bellaterra, SPAIN|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: In recent years, artificial metalloenzymes obtained by the insertion of a homogenous catalyst in abiomolecule have reached a privileged position in the field of man-tailored biocatalysis. Conceptually, their designaims at reproducing the same kind of the partnerships than those occurring between the heme and its receptors inhemoenzymes. Nonetheless, the non-natural interactions that govern these architectures are difficult to control.Amongst key elements for successful designs is the formation of a stable adducts between the homogenous catalystand the receptor and the formation of a pro-active artificial binding site. The later should allow substrate specificity andboth regio- and enantiocontrol of the reaction. For most of the geometrical and electronic factors that need to betuned, molecular modeling appears as an interesting ally. Nonetheless, the simultaneous exploration of wide chemicaland conformational spaces required in many aspects reaches further than standard methodologies.Our philosophy for the computer aided design of artificial metalloenzymes consists in a balanced combination ofprotein-ligand dockings, QM and QM/MM approaches and molecular dynamics. Here we present how theseintegrative approaches can accurately predict the binding of the organometallic moieties to biomolecular hosts, predictthe activation mechanism of the resulting composites and allow the characterization of their entire catalyticmechanism including for those systems providing with enantioselective excesses.(No Image Selected)

CONTROL ID: 1714706TITLE: Solid Artificial Metalloenzymes by Post-Engineering of Porous Protein CrystalsAUTHORS/INSTITUTIONS: T. Ueno, S. Abe, Graduate School of Bioscience and Biotechnology, Tokyo Institute ofTechnology, Yokohama, JAPAN|H. Tabe, Institute for Integrated Cell-Material Sciences , Kyoto University, Kyoto,JAPAN|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: The design of artificial metalloenzymes has been the focus of much attention in fundamental researchand development of applications in biotechnology. Conjugation of proteins to metal compounds is one of the mostconvenient methods used in the expansion of function of known proteins. Several artificial metalloenzymes have beendeveloped with non-covalent or covalent conjugation between proteins and synthetic metal cofactors. Recent progressin structural biology and computational approaches have enabled artificial metalloenzymes to be designed moreprecisely. Although a number of artificial enzymes exhibit high-performance catalytic activity and/or can be used in theelucidation of reaction mechanisms, they tend to be unstable and can only be used under limited conditions withoutrecyclability. Thus, the design of a protein composite that overcomes these issues is needed to obtain significantadvances in the field of artificial metalloenzymes. We have engineered hen egg white lysozyme (HEWL) crystals tocontain organometallic complexes so that the hybrid crystals can catalyze enantioselective hydrogen transfer. (1) T. Ueno, et al., Chem. Commun., 2013 49, 4114-4126 (Feature article).(2) T. Ueno, Chem. Euro. J., 2013, in press (Concept article).(3) T. Ueno, Chem. Asian. J., 2013, in press (Focus review).(4) S. Abe, et al., Small, 2012, 8, 1314-1319.(5) T. Koshiyama, et al., Angew. Chem. Int. Ed. 2011, 50, 4849-4852.(No Image Selected)

CONTROL ID: 1714802TITLE: The role of a nonheme FeOOH in aromatic hydroxylation : a mechanistic study under single turnover andcatalytic conditionsAUTHORS/INSTITUTIONS: F. Banse, A. Thibon, V. Jollet, K. Senechal-David, L. Billon, Institut de Chimie Moleculaireet des Materiaux d'Orsay, Universite Paris Sud, Orsay, FRANCE|A.B. Sorokin, Institut de Recherches sur la Catalyseet l'Environnement de Lyon, CNRS-Université Lyon 1, Villeurbanne, FRANCE|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: Inspired by iron enzymes catalyzing hydrocarbon oxidation by dioxygen in the presence of reducingequivalents, numerous studies have been dedicated to small organic susbtrates oxidation by hydrogen peroxidecatalyzed by synthetic iron complexes. Nonheme FeII complexes supported by amine/pyridine ligands have allowed togenerate FeIII(OOH) intermediates[1] but their role as key oxidants is still a matter of debate. Among numeroussynthetic low spin FeIII(OOH) complexes characterized to date, [(L5

2)Fe(OOH)]2+ is the only one that has beenisolated in the solid state at low temperature.[2] This has provided the unique opportunity to study its oxidizingproperties under single turnover conditions.Kinetic monitoring of [(L5

2)Fe(OOH)]2+ decay in acetonitrile in the presence of aromatic substrates such as anisoleand benzene, as well as analysis of the rate of formation of the phenol products have been performed at differenttemperatures and under different single turnover experimental conditions. Combining these data with the onesgrasped from experiments under catalytic conditions by using the substrate 1,3,5-[D3]-benzene and spin trappingexperiments in the presence of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) has allowed us to clarify the role played byFeIII(OOH) in aromatic oxidation.[3]For more general considerations, the mechanism drawn from our experiments will be compared to the ones proposedfor related systems with tetradentate amine/pyridine ligands.[4] [1]Girerd, J. J.; Banse, F.; Simaan, A. J. Struct. Bond. 2000, 97, 145.[2]Martinho, M.; Dorlet, P.; Riviere, E.; Thibon, A.; Ribal, C.; Banse, F.; Girerd, J.-J. Chem. Eur. J. 2008, 14, 3182.[3]Thibon, A.; Jollet, V.; Ribal, C.; Sénéchal-David, K.; Billon, L.; Sorokin, A. B.; Banse, F. Chem. Eur. J. 2012, 18,2715.[4]a) Makhlynets, O. V.; Rybak-Akimova, E. V. Chem. Eur. J. 2010, 16, 13995; b) Prat, I.; Mathieson, J. S.; Guell, M.;Ribas, X.; Luis, J. M.; Cronin, L.; Costas, M. Nat. Chem. 2011, 3, 788.

CONTROL ID: 1715811TITLE: From “Hemoabzymes” to “Hemozymes” : towards new biocatalysts for selective oxidationsAUTHORS/INSTITUTIONS: J. Mahy, M. Allard, R. Ricoux, ICMMO, UMR 8182 CNRS, Université Paris-Sud, Orsay,FRANCE|B. Golinelli, LEBS, CNRS, Gif/Yvette, FRANCE|J. Maréchal, Dep. de Chimica, Univ. Barcelona, Barcelona,SPAIN|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: The design of artificial hemoproteins that are able to catalyze oxidation reactions under a wide range ofconditions and to use clean oxidants such as O2 or H2O2, fits the current concept of “green chemistry” in a globalcontext of “sustainable growth”. In vivo, such reactions are performed by a wide class of heme-thiolate proteins,cytochromes P450, that catalyze the oxidation of drugs, using dioxygen as oxidant, in the presence of electronsdelivered from NADPH by cytochrome P450 reductase.Several strategies were used to design new artificial hemoproteins to mimic these enzymes, that associate a syntheticiron(III)-tetraarylporphyrin, to mimic the heme of P450s, to a protein that is supposed to mimic the apoprotein ofP450s, and selectively position the substrate with respect to the iron atom and to induce a selectivity in the catalyzedreaction.A first generation of artificial hemoproteins or “Hemoabzymes”, was obtained by the non-covalent association of asynthetic Fe(III)-α3β-tetra-o-carboxyphenylporphyrin (FeToCPP) or of a microperoxidase 8 (MP8) with monoclonalantibodies raised against these cofactors. The later MP8-antibody complexes were shown to catalyze the regio-selective nitration of phenol derivatives by H2O2/NO2 and the stereo-selective oxidation of organic compounds suchas sulphides by H2O2. A second generation of artificial hemoproteins or “Hemozymes”, was obtained by the non-covalent association of anon-relevant protein with a tetraarylporphyrin. Several strategies were used, the most successful of which, named“host-guest” strategy involved the non-covalent incorporation of water-soluble anionic iron-porphyrins into xylanase Afrom Streptomyces Lividans, that was low-cost, available in large quantities, and, in addition, heat-resistant. Theartificial hemoproteins obtained were found able to perform efficiently the stereoselective oxidation of organiccompounds such as sulphides and alkenes by H2O2 and KHSO5.New strategies aiming at using dioxygen as an oxidant, are currently investigated.

Two generations of artificial hemoproteins: Antibody 13G10-Fe(ToCPP) Hemoabzyme and Xylanase A-Mn(ToCPP)Hemozyme

CONTROL ID: 1716211TITLE: Second Coordination-sphere Effects Increase the Catalytic Efficiency of Hydrolases BiomimeticsAUTHORS/INSTITUTIONS: A. Neves, H. Terenzi, B. Souza, T. Pacheco, Chemistry, Federal University of SantaCatarina, Florianópolis, Santa Catarina, BRAZIL|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: Phosphatases, oxidases and a variety of other enzymes have been successfully modeled throughmetal complexes that can reproduce their physico-chemical properties and even their catalytic activity, however with amuch lower efficiency [1,2].As has been suggested, these discrepancies in catalytic efficiency between model compounds and true enzymes are,by a large extent, due to the lack of many important intramolecular interactions in the second-coordination sphere ofthe model systems in comparison to the enzyme [2].In this work we propose a new extension of dinuclear hydrolases models by binding the Fe(III)M(II) (M(II) = Zn, Cu)catalytic unit to a small polyethyleneimine chain (PEI, 1200 Da) that can emulate the enzyme microenvironmentaround the active site (Fig. 1) [2]. In addition we also present the synthesis, characterization and hydrolase activity ofconjugates in which the well known DNA intercalator pyrene is anchored to the Fe(III)M(II) catalytic center [3]. Acknowledgment: CNPq and INCT-catálise References:1) Mitic, N.; Smith, S. J.; Neves, A.; Guddat, L. W.; Gahan, L. R.; Schenk, G. Chem. Rev. 2006, 106, 3338. 2) Mancin,F.; Scrimin, P.; Tecilla, P. Chem. Commnun., 2012, 48, 5545. 3) Neves et al, Inorg. Chem. 2013, 52, 3594.

Fig. 1

CONTROL ID: 1719150TITLE: Redox and Enzymatic activity of Type 2 Cu(His)3 Systems in de Novo Designed ConstructsAUTHORS/INSTITUTIONS: V.L. Pecoraro, F. Yu, Chemistry, Univ Michigan, Ann Arbor, MI, Michigan, UNITEDSTATES|M. Tegoni, chemistry, university of parma, parma, ITALY|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: We have used de novo metalloprotein design to understand heavy metal toxicity in a variety ofsystems and to prepare the most active analogous of the hydrolytic enzyme carbonic anhydrase. In this presentation,we will discuss our strategy for preparing type 2 copper protein mimics for the redox center in PeptidylhydroxylatingMonoxygenase and the Cu nitrite reductase. These de novo systems have a general structural resemblance to thenative systems and exhibit the requisite enzymatic activity. We will show how systematic surface modification of theproteins allows us to control the reduction potential of the centers and enhance the catalytic efficiency of the system.If time permits, we may also discuss other related systems.(No Image Selected)

CONTROL ID: 1720861TITLE: Reactivity of Ruthenium(IV)-Oxo Complexes: Mechanistic Insights into Oxidation Reactions of OrganicSubstrates and Application to Photocatalytic OxidationsAUTHORS/INSTITUTIONS: T. Kojima, Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki, JAPAN|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: High-valent metal-oxo complexes have been recognized as reactive intermediates in many kinds ofoxidative conversion of substrates performed by metalloenzymes. As functional models to elucidate the reactionmechanisms of substrate oxidations, Ru(IV)-oxo complexes have been also investigated for a long time. We willpresent our recent progress in the study on reaction mechanisms of oxidations of organic substrates by Ru(IV)-oxocomplexes. In acidic buffer solutions, [Ru(TPA)(H2O)2]2+ (1),1 [Ru(6-COO–-TPA)(H2O)]+ (2),2 and [Ru(N4Py)(H2O)]2+ (3)3

have been revealed to perform efficient and selective oxidations of organic substrates. In those reactions, complexes1 – 3 are converted to be corresponding Ru(IV)-oxo complexes, [RuIV(O)(TPA)(H2O)]2+ (4), [RuIV(O)(6-COO–-TPA)(H2O)]+ (5), and [RuIV(O)(N4Py)(H2O)]2+ (6), respectively, which can act as reactive species in the oxidationreactions. We have conducted detailed kinetic study on the oxidation reactions of alcohols in aqueous buffer solutions to revealthat the reactions proceed via the formation of oxidant-substrate adducts. Activation parameters obtained for theoxidations of alcohols by 4 – 6 were almost the same for each substrate, indicating that the three oxidants oxidize thesubstrates via similar transition states. Kinetic isotope effects (KIEs) in the methanol oxidation by the three Ru(IV)-oxocomplexes were 1.7-2.5 for the methyl group, however, no KIEs were observed for the hydroxyl group, indicating thatthe H-atom abstraction from the methyl group is rate-limiting.3 The complexes 1 – 3 can perform photocatalytic oxidation of organic substrates in acidic buffer solutions in thepresence of [Ru(bpy)3]2+ as a photosensitizer to exhibit high turnover frequencies up to 14,000 h-1.4 References 1.T. Kojima et al., Angew. Chem., Int. Ed. 2008, 47, 5772.2.T. Kojima et al., Angew. Chem., Int. Ed. 2010, 49, 8449.3.S. Ohzu et al., Chem. Sci. 2012, 3, 3421.4.S. Ohzu et al., Chem. Eur. J. 2013, 19, 1563.

Figure: Structures of Ru^II-aqua (<b>1</b> - <b>3</b>) and Ru^IV-oxo complexes (<b>4</b>- <b>6</b>).

CONTROL ID: 1720921TITLE: O2 Reduction Reaction by Iron Porphyrin Electrocatalyst: Biochemical electrodes and In-situ MechanisticInvestigationsAUTHORS/INSTITUTIONS: A. Dey, Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata,West Bengal, INDIA|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: Biochemical electrodes are designed and constructed to catalyze oxygen reduction reaction (ORR).These electrodes utilize the biochemical models of cytochrome c oxidase (CcO) and nitric oxide reductase (NOR)constructed using site directed mutants of myoglobin (Mb). Dynamic electrochemical investigations indicate that theseelectrodes catalyze 4e-/4H+ reduction of O2 to H2O with a 2nd order rate constant of ~107 M-1s-1 which is two ordersof magnitude higher than that of native CcO. These scaffolds utilize the fast O2 binding site of Mb and the directcovalent attachment of the heme group to the electrode resulting in the fastest group of ORR catalysts reported so far.The intermediates formed on the electrodes during ORR are identified using in-situ SERRS. The data indicateformation of low-spin FeIII-OOH, FeIV=O and high spin FeII species during steady state electrocatalytic ORR by ironporphyrin catalysts.

CONTROL ID: 1721499TITLE: Making and breaking the O−O bond at molecular iron catalystsAUTHORS/INSTITUTIONS: M. Costas, Z. Codola, O. Cusso, I. Prat, J. Lloret, J. Serrano, A. Company, X. Ribas,Universitat de Girona, Girona, SPAIN|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: The formation and cleavage of the O-O bond is arguably the most important reaction in livingorganisms. Reductive O-O breakage takes place in cytochrome C oxidase.[1] This reaction constitutes the basicconstituent of cellular respiration in aerobic organisms, and represents a primary source of energy. O-O cleavage alsotakes place in oxygenases,[2] and this reaction results in the generation of highly electrophilic high valent metal-oxospecies, responsible for oxidative transformations. On the other hand, O-O bond formation takes place at a Mn4Cacluster in the Oxygen Evolving Center of Photosystem II (PSII) of green plans and some bacteria. In both oxidativeand respiration enzymes, metal ions adopting high oxidation states result from reductive O-O cleavage reactions whilein PSII they are responsible for O-O bond formation.[3]Selected coordination complexes that reproduce structural aspects of enzymatic active sites have been shown tocatalyze analogous reactions, and recently some of these complexes have turned into very attractive tools for organicsynthesis.[4] In addition, the study of the mechanisms of action of these catalysts has shed light into the moleculardetails of enzymatic systems. Our research group undertakes this approach and aims at studying the chemistry of ironcoordination complexes with chemically robust nitrogen-based ligands, and which can sustain high oxidation states.[5-6] [1] S. Ferguson-Miller, G. T. Babcock, Chem. Rev. 1996, 96, 2889-2907.[2] a) M. Costas, M. P. Mehn, M. P. Jensen, L. Que, Jr., Chem. Rev. 2004, 104, 939-986. b) E. G. Kovaleva, J. D.Lipscomb, Nat. Chem. Biol. 2008, 4, 186-193.[3] Y. Umena, K. Kawakami, J.-R. Shen, N. Kamiya, Nature 2011, 55.[4] L. Que, W. B. Tolman, Nature 2008, 455, 333-340.[5] a) A. Company et al. Chem. Eur. J. 2008, 14, 5727. b) I. Prat et al. Nat. Chem. 2011, 3, 788.[6] J. Lloret-Fillol Nat. Chem. 2011, 3, 897(No Image Selected)

CONTROL ID: 1721584TITLE: DNA and Protein based artificial metalloenzymes for asymmetric catalysisAUTHORS/INSTITUTIONS: G. Roelfes, Stratingh Institute for Chemistry, University of Groningen, Groningen,NETHERLANDS|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: The catalytic efficiency and high selectivities achieved by natural metalloenzymes are a source ofinspiration for the design of novel bio inspired catalysts. An emerging approach for creating artificial metalloenzymesinvolves incorporating a synthetic transition metal catalysts into a biomolecular scaffold such as a protein or DNA. [1] In DNA-based asymmetric catalysis,[2] a transition metal catalyst is brought in close proximity of the DNA doublehelix, allowing for transfer of chirality to the catalyzed reaction. This concept has been applied successfully in severalof the archetypical C-C bond forming reactions[3] and the first catalytic enantioselective syn-hydration of enones,[4] areaction for which there is no alternative using conventional homogeneous catalysis. Several several newenantioselective reactions, such as Cu(I) catalyzed cyclopropanations[5] and catalytic asymmetric protonations inwater will be discussed.In an alternative approach we have converted the transcription factor LmrR (Lactococcal multidrug resistanceRegulator) into an artificial metalloenzyme. LmrR was selected as the protein scaffold because it contains a largehydrophobic pocket on the dimer interface. A residue inside the pocket was mutated to a cysteine and this was usedfor conjugation of a phenanthroline moiety. The resulting artificial metalloenzyme gave rise to up to 94 % ee in theCu2+ catalyzed Diels-Alder reaction.[6] [1] F. Rosati, G. Roelfes, ChemCatChem 2 (2010) 916-927.[2] G. Roelfes, B.L. Feringa, Angew. Chem. Int. Ed. 44 (2005) 3230-3232.[3] J. Oelerich, G. Roelfes, DNA-Based Metal Catalysis, in K.D. Karlin (Ed.), Progress in Inorganic Chemistry vol 57,John Wiley & Sons, Inc., Hoboken, New Jersey, 2012, pp 353-393.[4] A.J. Boersma, D. Coquière, D. Geerdink, F. Rosati, B.L. Feringa, G. Roelfes, Nat. Chem. 2, (2010), 991-995.[5] J. Oelerich, G. Roelfes, Chem. Sci. 4 (2013) 2013- 2017[6] J. Bos, F. Fusetti, A.J.M. Driessen, G. Roelfes, Angew. Chem. Int. Ed. 51 (2012) 7472-7475.

DNA-based catalytic enantioselective syn-hydration of enones and active site of the artifical metalloenzyme based onLmrR

CONTROL ID: 1721700TITLE: Calcium Manganese Oxides as Solid State Models for Biology's Water-Oxidation CatalystAUTHORS/INSTITUTIONS: P. Kurz, Institute for Inorganic and Analytical Chemistry, Albert-Ludwigs-UniversityFreiburg, Freiburg, GERMANY|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: Green plants and algae obtain the reduction equivalents for CO2-fixation through the processes ofoxygenic photosynthesis. One of the fundamental reactions of this cascade of reactions is the oxidation of water tomolecular oxygen (eq. 1), which takes place in the very large membrane protein ensemble Photosystem II (PSII). A μ-oxido-Mn4Ca-cluster, the oxygen-evolving-complex (OEC), has been identified as the biological catalytic site. 2 H2O => O2 + 4H+ + 4e- (1) After decades of extensive PSII-research, bioinorganic chemists have been able to reveal many key aspects of theOEC’s geometry and mode of action – e.g., the determination of a high-resolution PSII structure from X-ray datarepresents a recent highlight in this field.[1]Consequently, one might dare to say that looking at the large variety of known catalysts for (1), no catalytic water-oxidation process is as well understood as the one catalyzed by the OEC within PSII. For many other metalloenzymes(catalases, hydrogenases, tyrosinase...) a detailed knowledge about their catalytic sites has been accompanied by thesuccessful development of model chemistry in the form of coordination compounds. Not so for the OEC: despite thesynthesis of various multinuclear manganese complexes, it has so far not been possible to find a convincing functionalmolecular OEC-model compound. In the footsteps of earlier work along these lines,[2] we have developed an alternative approach and studiedmanganese oxide particles as solid-state OEC-model. By careful analysis of their composition, atomic structure andcatalytic properties for reaction (1) we were indeed able to identify a number of properties in catalytically active Mn-oxides which are strikingly similar to central features of the OEC (see Fig.).[3]The presentation will try to demonstrate that the OEC of Photosystem II might indeed be a case where solid statecompounds represent the so far best models for a bioinorganic active site. [1] Y. Umena et al., Nature, 473, 55-60 (2011).[2] V. Y. Shafirovich et al., J. Inorg. Biochem., 15, 113-129 (1981).[3] M. Wiechen et al., Chem. Sci., 3, 2330-2339 (2012)

CONTROL ID: 1721938TITLE: Biomimetic models of hydrogenases: impact of redox-active ligandsAUTHORS/INSTITUTIONS: A.K. Jones, L. Gan, S. Roy, T.L. Groy, Department of Chemistry and Biochemistry,Arizona State University, Tempe, Arizona, UNITED STATES|A.K. Jones, Center for Bioenergy and Photosynthesis,Arizona State University, Tempe, Arizona, UNITED STATES|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: Hydrogenases, with turnover numbers in the thousands per second, serve as a gold standard indeveloping non-precious metal catalysts for electrocatalytic production of hydrogen via reduction of protons forrenewable energy applications. Although the two major types of hydrogenases, [NiFe] and [FeFe], are notevolutionarily related, they are remarkably similar chemically. Nonetheless, it has proven challenging to create robust,simpler functional models based on these enzymes. The goal of this study was to evaluate the impact of bidentate,redox non-innocent ligands on the electrocatalytic properties of [NiFe] and [FeFe]-hydrogenase models. Thesynthesis, structures, and electrocatalytic activities of two new complexes will be presented. The diiron complex (μ-S(CH3)SFe2(CO)4(κ2-bpy) for bpy=2,2’-bipyridyl undergoes a two electron reduction at -2.06 V vs. Fc+/Fc and is acompetent catalyst for reduction of protons. The catalytic potential is milder than anticipated based on comparison toother [FeFe]-hydrogenase model compounds. The complex [Ni(bdt)(dppf)] for bdt=1,2-benzenedithiol and dppf=1,1’-Bis(diphenylphosphino)ferrocene is a fast proton reduction catalyst (1240 s-1) with very modest electrochemicaloverpotential (265 mV). Both of these complexes suggest that redox active ligands can be powerful tools for tuning theelectrocatalytic properties of coordination catalysts for multielectron redox transformations.

CONTROL ID: 1728837TITLE: Water oxidation by amorphous transition metal oxides: Quasi-molecular materials resembling the biologicalcatalyst of photosynthesisAUTHORS/INSTITUTIONS: H. Dau, Z. Ivelina, M. Risch, P. Chernev, J. Heidkamp, K. Klingan, M. Gleich, D.Gonzales, FB Physik, Freie Universität Berlin, Berlin, GERMANY|M. Risch, Electrochem energy Lab, MIT, Boston,Massachusetts, UNITED STATES|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: In the light of global climate change, the development of new systems for efficient production of non-fossil fuels from abundant resources (water, carbon dioxide, light energy,..) is highly desirable. Any attractive systemfor 'ab-initio' fuel production comprises water oxidation. The desirable catalysts are based on (i) abundant elements,and (ii) can operate under benign conditions (room temperature, avoidance of extreme pH values) (1). The biologicalcatalyst of photosynthesis, the protein-bound Mn4Ca(µ-O)5 cluster of photosystem II, fulfills these requirements.However, mimicking the biological paragon in form of molecular manganese complexes has not lead to atechnological breakthrough. In 2008, Kanan and Nocera described a cobalt-based catalyst system for water oxidationin the neutral pH regime (2). Since then, numerous researchers have focused on the development of new water-oxidation catalyst based on first-row transition metals. In this presentation, oxides based on Co, Ni, and Mn arecompared and common properties are discussed. These oxides share common structural motifs (3-6) and can be bi-functional (7). They perform well in water oxidation if present in form of a non-crystalline, hydrated material. Theseoxides are redox-active meaning that the metal ions undergo oxidation-state and structural changes when exposed tovarious (electrode) potentials in the vicinity of the water-oxidation equilibrium potential. Oxidation state changes canbe described in terms of proton-coupled electron transfer reactions involving short-range and long-distance protontransfer. A conceptual approach is outlined for description of the mode of water oxidation in these heterogeneouscatalysts. Surprising structural and functional similarities to the biological catalyst are discussed.1.Dau, H et al. (2010) ChemCatChem 2, 724-7612.Kanan, M. W et al. (2008) Science 321, 1072-10753.Risch, M. et al. (2012) ChemSusChem 5, 542-5494.Zaharieva, I. et al. (2012) Energy Environ. Sci. 5, 7081-70895.Wiechen, M. et al.(2012) Chemical Science 3, 2330-23396.Zaharieva, I. et al.(2011) Energy Environ. Sci. 4, 2400-24087.Cobo, S. et al. (2012) Nature Materials 11, 802-807.(No Image Selected)

Found 3 Abstracts CONTROL ID: 1711634TITLE: Artificial Photosynthesis for Production of Hydrogen Peroxide as a Solar fuelAUTHORS/INSTITUTIONS: S. Fukuzumi, Osaka University, Suita, JAPAN|S. Fukuzumi, Ewan Womans University,Seoul, KOREA, REPUBLIC OF|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: Photosynthesis consists of several steps: light harvesting and charge-separation steps in thephotosynthetic reaction center and catalytic steps for water oxidation and reduction, and also a catalytic step for CO2fixation. This lecture presents our recent development on each step of bioinspired artificial photosynthesis withcatalytic steps for water reduction and oxidation as well as CO2 fixation. A rational design of the photosyntheticreaction center models has been made based on the Marcus theory of electron transfer. A variety of photosyntheticreaction center efficient models composed of electron donors and acceptors linked by covalent bonding have beendeveloped including multi-component systems.[1,2] The combination of light harvesting and charge-separation stepshas also been achieved by the rational design of supramolecular electron donor-acceptor ensembles, providing avariety of applications including efficient photocatalytic systems for the solar energy conversion and construction oforganic solar cells.[3]The efficient charge-separation step has been successfully combined with the catalytic waterreduction step to attain the most efficient photocatalytic hydrogen evolution system by developing the structural andfunctional model of hydrogenases.[4,5] The hydrogen storage system is also presented by the catalytic fixation of CO2with H2 as a form of formic acid,[6] together with interconversion between H2 and H2 storage compounds.[7] Thephotocatalytic water oxidation to produce hydrogen peroxide as an environmentally benign fuel will also be reportedtogether with the development of hydrogen peroxide fuel cells.[8](1)S. Fukuzumi et al. , 10, 2283 (2008).(2)S. Fukuzumi, et al. Proc. Natl. Acad. Sci. USA, 109, 15572 (2012). (3)S.Fukuzumi et al. Chem. Commun., 48, 9808 (2012).(4)S. Fukuzumi, et al.J. Mater. Chem., 22, 24284 (2012).(5)Y.Yamada, et al. J. Am. Chem. Soc., 133, 16136–16145 (2011).(6)Y. Maenaka, et al. Energy Environ. Sci., 5,7360–7367 (2012).(7)Y. Maenaka, et al. J. Am. Chem. Soc., 134, 9417–9427 (2012).(8)D. Hong, et al. J. Am. Chem. Soc., 134, 19572-19575 (2012).(No Image Selected)

CONTROL ID: 1718356TITLE: The High-Valent Iron-Oxo Reactivity Landscape AUTHORS/INSTITUTIONS: L. Que, Chemistry, University of Minnesota, Minneapolis, Minnesota, UNITED STATES|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: Biological oxidation reactions are often catalyzed by metalloenzymes via high-valent iron centers thatare generated through dioxygen activation. Examples include the Fe(IV)=O oxidants associated with TauD and relatedmononuclear nonheme iron oxygenases and the Fe(IV)2(μ-O)2 intermediate Q of methane monooxygenase. Ourrecent efforts have focused on generating synthetic analogs of such reactive species, usually at lower temperature inorder to stabilize them, and then using a variety of spectroscopic methods to characterize their geometry and ligandenvironment, as well as the oxidation and spin state of the iron center. These variables are likely to be factors thatcontrol their reactivity towards C–H and C=C bonds. Insights into how these factors affect the reactivity of the high-valent Fe=O unit should enhance our understanding of the enzymatic mechanisms as well as contribute to the designof better bio-inspired oxidation catalysts. Some of our latest results will be discussed. (No Image Selected)

CONTROL ID: 1721876TITLE: Functional Models of Fe(d) in the [FeFe] Hydrogenase Active SiteAUTHORS/INSTITUTIONS: S. Ott, Uppsala University, Uppsala, SWEDEN|CURRENT CATEGORY: Bioinspired CatalysisABSTRACT BODY: Abstract Body: The dinuclear active sites of [FeFe] hydrogenase enzymes catalyze the interconversion of protons tohydrogen at high rates and low overpotentials. Their bioinorganic model complexes still do not live up to the enzyme’sperformance, despite of having been in the center of attention for more than a decade. In this presentation, we discussa new approach to mimic the protein environment that facilitates the high reactivity of the [FeFe] hydrogenase activesite. Mononuclear iron complexes with structural features of the “catalytic” Fe center of the active site, the so-calleddistal Fe(d), will be presented, and their performance as proton reduction catalysts will be examined. The mechanismfor electrochemical proton reduction catalyzed by a mononuclear iron complex will be discussed in detail.(No Image Selected)