Zinc Coordination Polymers Containing the m-(2-thiazolyl)benzoic Acid Spacer: Synthesis, Characterization and Luminescent Properties in Aqueous Solutions

Four 1D coordination polymers have been prepared, starting from ZnII salts and the organic linker m-(2-thiazolyl)benzoic acid (HL), also combined with auxiliary ligands: [Zn2(L)4(H2O)·2(MeCN)]1 (1), [Zn2(L)3(NO3)(bipy)]1 (2; bipy = 4,4'-dipyridyl), [Zn2(L)4(bipy)]1 (3), [Zn2(L)4(PyEtPy)]1 [4; PyEtPy = 1,2-bis(4-pyridyl) ethane]. In all species, the Zn2(carboxylate)4 "paddle-wheel" dimer is the constituting inorganic node, where the carboxylate groups from L- are bridging two adjacent metal centers. The square pyramidal metal coordination environment is completed by aquo ligands and the N(thiazole) atoms (in 1) or by the N donors from auxiliary bridging spacers like bipy (in 2 and 3) or PyEtPy (in 4). The luminescent properties in aqueous solutions of 3 and 4 have been examined. The N and S donors dangling from the thiazole rings in these polymers can engage into further supramolecular interactions with (acidic) metal cations, inducing a luminescence quenching after complexation. The interaction of 3 and 4 with HgII (in the form of its chloride salt HgCl2) has been analyzed as a representative example of this behaviour.