Structural Diversity and Properties of Coordination Polymers Built from a Rigid Octadentenate Carboxylic Acid

By using a rigid octadentenate carboxylate linker 5,5′,5″,5″′-silanetetrayltetraisophthalic acid (H8L), three new microporous coordination polymers, namely, [Cu4L­(H2O)4]·2DMF·10H2O (1), [Zn5L2(H2O)4]­[NH2(CH3)2]6·2DMF·4H2O (2), and [Cd3(H2L)2]­[NH2(CH3)2]6·4DMF·14H2O (3), were solvothermally synthesized and structurally characterized. Compound 1 is a 3D framework built from a square paddlewheel [Cu2(O2CR)4] and a 8-connected cube L ligand to give a (4,8)-connected scu structure. Compound 2 is a 3D 4-nodal (4,4,4,8)-connected network with small 1D channels built on three tetrahedral Zn units and a 8-connecting ligand L. Compound 3 possesses a 3D structure with a (4,4,6)-connected net built on two tetrahedral Cd units and a 6-connecting ligand H2L6–. All the three compounds consist of large solvent accessible voids, but only compound 1 possesses permanent porosity as confirmed by N2, H2, O2, CO2 and CH4 gas adsorption measurements. Compounds 2 and 3 exhibited strong blue fluorescent emissions with a peak at 414 and 412 nm, respectively, at RT upon excitation owing to a ligand-centered excited state.