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: [Zn-2(L)(4)(H2O).2(MeCN)](infinity) (1), [Zn-2(L)(3)(NO3)(bipy)](infinity) (2; bipy = 4,4'-dipyridyl), [Zn-2(L)(4)(bipy)](infinity)(3), [Zn-2(L)(4)(PyEtPy)](infinity)[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.