A coordination polymer of CdCl2 with the novel zwitterionic dicarboxylate ligand 2,2'-(2-methylbenzimidazolium-1,3-diyl)diacetate (pda).

The title compound, poly[chlorido[mu(4)-2,2'-(2-methylbenzimidazolium-1,3-diyl)diacetato]cadmium(II)], [Cd(C(12)H(11)N(2)O(4))Cl](n), is an undulating two-dimensional polymer consisting of a paddlewheel Cd(2)(CO(2))(4) cluster which lies on an inversion centre. These paddlewheel clusters act as four-connected square building units interlinked via bridging zwitterionic dicarboxylate ligands into a corrugated layer which is consolidated by pi-pi interactions between benzene rings of benzimidazole groups. Neighbouring layers are further assembled via interlayer pi-pi interactions into a three-dimensional supramolecular structure. The key feature of this study is the synthesis of a paddlewheel-based polymer constructed with a novel multifunctional zwitterionic dicarboxylate ligand.