A novel two-dimensional Cd(II) coordination polymer: poly[aqua[μ₄-2-(4-carboxylatobenzoyl)benzoato]cadmium(II)].

The title Cd(II) coordination framework, [Cd(C15H8O5)(H2O)]n or [Cd(bpdc)(H2O)]n [H2bpdc is 2-(4-carboxybenzoyl)benzoic acid], has been prepared and characterized using IR spectroscopy, elemental analysis, thermal analysis and single-crystal X-ray diffraction. Each Cd(II) centre is six-coordinated by two O atoms from one 2-(4-carboxylatobenzoyl)benzoate (bpdc(2-)) ligand in chelating mode, three O-donor atoms from three other bpdc(2-) anions and one O atom from a coordinated water molecule in an octahedral coordination environment. Two crystallographically equivalent Cd(II) cations are bridged by one O atom of the 2-carboxylate group of one bpdc(2-) ligand and by both O atoms of the 4-carboxylate group of a second bpdc(2-) ligand to form a binuclear [(Cd)2(O)(OCO)] secondary building unit. Adjacent secondary building units are interlinked to form a one-dimensional [Cd(OCO)2]n chain. The bpdc(2-) ligands link these rod-shaped chains to give rise to a complex two-dimensional [Cd(bpdc)]n framework with a 4,4-connected binodal net topology of point symbol {4(3).6(2).8}. The compound exhibits a strong fluorescence emission and typical ferroelectric behaviour in the solid state at room temperature.