摘要:
IntroductionAssembling extended structure compounds by selecting organic spacers (e.g.4,4′bipyridine, pyrazine, dicarboxylic acids,etc.) and inorganic metal ion species of suitable chemical structure and coordination geometry, respectively, may yield a series of novel networks with various sizes and shapes of void space or cavity.1Such types of materials are being investigated intensively because of their multidimensional applications in the field of catalysis,2anonlinear optics,2belectrical conductivity,2cmolecular recognition2dand molecular sieves.2eAmong the different organic spacers, the squarate dianion (C4O42−) is an interesting cyclic compound with aromaticity andit can function as a bridging ligand with possible μ2, μ3 and μ4 between metal ions3(Scheme 1). The most fully investigated metal squarate is M(C4O4)(H2O)4[M⊕=⊕Mn(ii), Co(ii), Ni(ii), Fe(ii), Zn(ii) and Cu(ii)]4with two bridging C4O42−(μ2) ligands attranspositions, which form an infinite chain structure. Each metal ion is also bonded with four water molecules to form a distorted octahedral geometry. West and Niu5first reported another type of metal squarate with the formula M(C4O4)(H2O)2[M(ii)⊕=⊕Fe(ii),Co(ii), Ni(ii) and Zn(ii)]. Later three-dimensional cubic structures were found to have the formula M(C4O4)(H2O)2[M⊕=⊕Ni(ii)6and Fe(ii)4b], M(C4O4)(H2O)2(MeCO2H·H2O)1/3[M⊕=⊕Zn(ii), Ni(ii) and Mn(ii)]7and Co(C4O4)(H2O)2·0.33H2O4b, where C4O42−functions as a bridging ligand between four metal ions (μ4).Besides these two types of metal squarate, another type with the formula M(HC4O4)2(H2O)4[M⊕=⊕Fe(ii)4band Mn(ii)8] has been found, which is a two-dimensional sheet-like network built from (HC4O4)2and M(H2O)4units.Binding modes of the squarate dianion.In the course of our studies on polymeric coordination compounds9here we have chosen cadmium(ii) as the metal ion due to its d10configuration, which permits a wide variety of geometries and coordination numbers, with the squarate dianion as an effective building block in order to synthesize an uncharged polymeric network. Here, we report a bridging μ4 squarate coordination polymer of cadmium(ii), exhibiting a 3D channel network, and solid state thermal studies, which show that the cadmium squarate framework is remarkably stable after dehydration.
ISSN:1466-8033
DOI:10.1039/b105080j
出版商:RSC
年代:2001
数据来源: RSC