A Series of Cadmium(II) Coordination Polymers Synthesized at different pH Values

A new family of cadmium(II) coordination polymers, {[Cd(Hbic)2·(H2O)2]·2H2O}n (1), [Cd(Hbic)2]n (2), [Cd(Hbic)2·(H2O)]n (3), H2bic = 1H‐benzimidazole‐5‐carboxylic acid, has been hydrothermally prepared by the assembly of CdII with H2bic. A change in the pH values resulted in a series of compounds with different compositions and dimensionalities. Formed at the lowest pH, compound 1 has a two‐dimensional supramolecular structure, which contains 1D chains extended by hydrogen bonds. At a slightly higher pH, compound 2 is synthesized with a higher number of deprotonated carboxylate groups per cadmium atom. A further increase in the pH leads to 3D dinuclear compound 3 with yellow‐green emitting fluorescence. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)