A Novel Three-Dimensional Network Containing Mn(II) Ions andTricyanomethanide with Rare 46.64 Topology

Hao-Ling Sun,† Bao-Qing Ma,† Song Gao,*,† and Stuart R. Batten*,‡

College of Chemistry and Molecular Engineering, State Key Laboratory of Rare Earth MaterialsChemistry and Applications, PKU-HKU Joint Laboratory on Rare Earth Materials andBioinorganic Chemistry, Peking University, Beijing 100871, China and School of Chemistry,P.O. Box 23, Monash University, Clayton, Victoria 3800, Australia

Received March 6, 2005

ABSTRACT: A novel three-dimensional network Mn(tcm)2(bpeado) (1) (tcm ) tricyanomethanide, bpeado ) 1,2-bis(4-pyridyl)ethane-N,N′-dioxide) consisting of 5-connected Mn(II) ions with a rare 46.64 topology has been synthesized; twosuch nets interlock to generate a 2-fold interpenetrated structure. Variable temperature magnetic susceptibility studieshave shown that this compound displays weak antiferromagnetic coupling because of the long bpeado and tcm pathways.Consequently, no magnetic ordering was found.

Coordination networks are of great interest both for theirpotential applications in the field of materials1 and for theirintriguing architectures and topologies.2 The most usualand efficient strategy for synthesizing coordination net-works is based on a “building block” approach, and thetopology of the final structure is greatly dependent on thegeometry of the nodes (connection centers) and/or theflexibility of the “building blocks”. The tricyanomethanide[tcm, C(CN)3

-] ligand is a versatile “building block” forconstructing high-dimensional coordination polymers be-cause it has three potentially coordinating nitrogen atomsand several coordination modes observed, including mono-dentate, bidentate (µ1,5), tridentate (µ1,5,7), and tetradentate(µ1,1,5,7). The binary systems display either 2-fold interpen-etrated rutile networks for M(tcm)2 [M ) Cr(II), Mn(II),Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II)]3 ordoubly interpenetrated (6,3) sheets for Ag(tcm),4 in whichtcm serves as a µ1,5,7 tridentate bridge. In addition to thebinary systems, the introduction of co-ligands, such ascoordination solvent and ditopic ones, leads to a dramaticmodification in the structural motifs.5 Among such systems,particularly noteworthy are those containing Cu(I), Ag(I),or Cd(II) metal ions and bridging ligands, such as hexa-methylenetetramine, 4,4′-bipyridine (4,4′-bpy), 1,2-bis(4-pyridyl)ethane or pyrazine, which display interestingstructures with a variety of topologies including doublyinterpenetrated (4,4) sheets, 3D rutile networks, or 3Dnetworks with mixed 3- and 5-connecting centers.6 Bycontrast, the combination of the M-tcm binary system [M) Mn(II), Fe(II), Co(II), Ni(II), Cu(II)] with various co-ligands usually results in (4,4) sheets or one-dimensional(1D) chains bridged by µ1,5-tcm.7 Herein we reported a novel3D framework with a rare 46.64 topology containing 5-con-nected Mn(II) ions, tcm and 1,2-bis(4-pyridyl)ethane-N,N′-dioxide (bpeado) co-ligands, which was chosen based on thefollowing considerations: (a) the flexible angular connectionmodes of bpeado compared with that of 1,2-bis(4-pyridyl)-ethane;8 (b) the successful combination of heterocyclicN-oxide with dca reported in our previous work.9,10

Compound Mn(tcm)2(bpeado) (1) was prepared by mixingMnCl2‚6H2O, bpeado, and tcm in aqueous solution understirring.11 X-ray diffraction analysis revealed that 1 consistsof a 3D network containing both bpeado and tcm bridges.12

As shown in Figure 1, the structure of 1 contains octahedral

Mn atoms which lie on general positions and are coordi-nated to four tcm anions [Mn-N ) 2.228(2), 2.232(2),2.236(2), and 2.275(2) Å] and two cis disposed bpeadoligands [Mn-O ) 2.125(1) and 2.114(1) Å]. The tcm anionsbridge in a bidentate (µ1,5) fashion, connecting the Mnatoms into ladder-like motifs in which single tcm bridgesform the sides of the ladders, and double tcm bridges formthe rungs (Figure 1), which is similar to that found in a1D Cu-tcm complex.13 These ladders are then cross-linkedby the bridging cis bpeado ligands to generate a three-dimensional (3D) 5-connected network with 46.64 topology(Figure 2). Two such nets interpenetrate such that theladders are not penetrated. Rather, the four-memberedrings generated by the cross-linking of the ladders in thetwo nets are catenated (Figure 3). The Mn‚‚‚Mn separationis 7.435 Å across the single tcm bridges, 7.644 Å acrossthe double tcm bridges, and 14.93 Å across the bpeadobridges. The Mn‚‚‚Mn separations through tcm are shorter

* To whom correspondence should be addressed. E-mail: gaosong@pku.edu.cn (S.G.) and stuart.batten@sci.monash.edu.au (S.R.B.).

† Peking University.‡ Monash University.

Figure 1. Local coordination geometry and 1D ladder substruc-ture in the structure of 1. Metal atoms are depicted in pink, whilethe ligand atoms are depicted in green (carbon), blue (nitrogen),and red (oxygen); a lighter shade is used for the bpeado ligandscompared to the tcm anions.

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than those found in Mn(tcm)2,14 and the Mn‚‚‚Mn separa-tions through bpeado are longer than that found in theM(dca)2(bpeado) (dca ) dicyanamide) complexes.10

Structures containing 5-connected metal centers are veryrare,15 and the coordination polymer Cu(4,4′-bpy)1.5Cr2O7‚H2O is the only one reported example containing 5-con-nected metal centers with 46.64 topology.16 However, thereis also some difference between these two structures. In 1,there are six bridges around the metal centers; however,only five bridges were found in the previously reportedcompound. The difference comes from the different natureof the bridging ligands around the metal centers. The sterichindrance of three 4,4′-bipyridine bridges around theCu(II) ions means only two other Cr2O7 bridges arepossible. Compared with 4,4′-bipyridine, however, theextended oxygen atoms and the unique angular coordina-tion mode of bpeado decreases the steric hindrance ef-ficiently and makes it possible for the Mn(II) to adoptanother four tcm bridges.

The variable-temperature magnetic susceptibility øMfor a collection of crystals of 1 in the temperature range of1.9-300 K was measured in a field of 1000 Oe, and theresults are shown in Figure 4. The value of øMT at room

temperature, 4.26 cm3 mol-1 K, is in good agreement withthe spin-only value (4.38 cm3 mol-1 K) expected for anuncoupled Mn(II) system. The øMT value remains nearlyconstant to about 30 K then decreases rapidly to 1.38 cm3

mol-1 K at 1.9 K, which is similar to that found inMn(tcm)2.14 The magnetic susceptibilities of 1 can be fittedwell by the Curie-Weiss law ø ) C/(T - θ), with θ ) - 2.7K, C ) 4.31 cm3 mol-1 K for 1. The small negative θ valuesuggests a very weak antiferromagnetic interaction medi-ated by Mn-NtC-C-CtN-Mn pathways.

In conclusion, a novel three-dimensional network con-sisting of 5-connected Mn(II) ions with a rare 46.64 topologyhas been synthesized. Magnetic studies reveal that thiscompound is paramagnetic with weak antiferromagneticcoupling between the metal centers.

Acknowledgment. Financially supported by the Na-tional Natural Science Foundation of China (No. 20125104,20221101, 20490210), the National Key Project for Fun-damental Research (2003CCA00800), and the AustralianResearch Council.

Supporting Information Available: CIF files for the com-pound 1. This material is available free of charge via the Internetat http://pubs.acs.org.

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1999, 402, 276. (b) Noro, S.; Kitagawa, S.; Kondo, M.; Seki,K. Angew. Chem., Int. Ed. 2000, 39, 2081. (c) Zaworotko,M. J. Angew. Chem., Int. Ed. 2000, 39, 2113. (d) Kou, H. Z.;Gao, S.; Zhang, J.; Wen, G. H.; Su, G.; Zheng, R. K.; Zhang,X. X. J. Am. Chem. Soc. 2001, 123, 11809. (e) Ma, B. Q.;Sun, H. L.; Gao, S.; Su, G. Chem. Mater. 2001, 13, 1946. (f)Yeung, W. F.; Man, W. L.; Wong, W. T.; Lau, T. C.; Gao, S.Angew. Chem., Int. Ed. 2001, 40, 3031.

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Figure 2. Schematic representation of the 3D 5-connected 46.64

network structure of 1. Only metal atoms are shown, with the tcmlinks represented by the orange bonds, and the bpeado links, whichbridge the Mn(tcm)2 ladders, represented by the green bonds.

Figure 3. The two interpenetrating 3D nets in the structure of1; again only the Mn atoms are shown, and the tcm and bpeadolinks in each net are represented by different colored bonds.

Figure 4. Temperature dependence of øMT and 1/øM for 1. Thered line shows the best-fit curve according to the Curie-Weiss fitlaw.

1332 Crystal Growth & Design, Vol. 5, No. 4, 2005 Communications

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(11) Synthesis of 1: This was carried out by the mixing of0.25 mmol (50 mg) of MnCl2‚6H2O and 0.25 mmol (54mg) of bpeado in 15 mL of water. Ktcm (0.5 mmol, 65 mg)was added under stirring. The resulting yellow solutionwas filtered and allowed to stand at room temperature.Suitable yellow block single crystals were obtained in abouttwo weeks. The crystals were collected, washed with water,and dried in air (yield 90%). Elemental anal. Calcd for

C20H12MnN8O2: C, 53.23; H, 2.68; N, 24.83%. Found: C,53.13; H, 2.90; N, 25.09%. IR (cm-1): 2239 w, 2191 s, 2180s, 2168 s.

(12) Crystal data: compound 1: C20H12MnN8O2, M ) 451.32,monoclinic, space group P21/c, a ) 11.5319(3), b ) 24.2933-(5), c ) 7.4351(1) Å, â ) 95.1658(8)°, U ) 2074.47(7) Å3, Z) 4, Dc ) 1.445 Mg/m3, µ(Mo KR) ) 0.671 mm-1, F(000) )916, GOF ) 0.923. A total of 38 271 reflections werecollected and 4727 are unique (Rint ) 0.0840). R1 and wR2are 0.0335 and 0.0656, respectively, for 280 parameters and2859 reflections [I > 2σ(I)]. The data were collected on aNonius Kappa CCD with Mo KR radiation (λ ) 0.71073 Å)at 293 K. The structures were solved by direct methods andrefined by a full matrix least squares technique based onF2 using the SHELXL 97 program.

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(16) Pan, L.; Ching, N.; Huang, X. Y.; Li, J. Chem. Commun.2001, 1064.

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