Synthesis, structure, and luminescence properties of zinc(II) and cadmium(II) complexes containing the flexible ligand of 3,3′-thiodipropionic acid

Two coordination polymers with mixed-ligands, [ZnL(2,2'-bipy)H2O](n) (1) and [CdL(2,2'-bipy)](n) (2), (L=3,3'-thiodipropionic acid; 2, 2'-bipy=2, 2'-bipyridine) have been synthesized and structurally characterized. Crystal structures reveal that the synthesized complexes consist of a one-dimensional single-chain and a one-dimensional double-chain, respectively. A prominent feature of complex 1 is the formation of a vagarious double-chain by two neighboring single-chains interleaving with each other. It is interesting for complex 2 to assemble the double chain into a 2D ordered supramolecular structure via pi center dot center dot center dot pi stacking interactions. Moreover, elemental analysis, IR, and luminescent spectra of complexes 1-2 were also determined. At room temperature, complex I exhibits an intense emission at 360 nm upon 328 nm excitation, while complex 2 exhibits an intense emission at 472 nm upon 457 nm excitation, which can probably be assigned to the intraligand (pi - pi*) fluorescent emission.