Synthesis, crystal structures, and properties of three helical coordination polymers with quinolinecarboxylate ligand

Three mixed-ligand complexes [M(L)(Phen)(H2O)](n)center dot nH(2)O [M = Ni (1), Co (2), Zn (3)], (L = 2-methylquinoline-3,4-dicarboxylate dianion; phen 1,10-phenanthroline) have been synthesized by the reaction of MCl2 with 2-methylquinoline-3,4-dicarboxylate acid, sodium hydroxide, and 1,10-phenanthroline under hydrothermal conditions and were characterized by single-crystal X-ray diffraction. Complexes 1-3 crystallize isomorphously in the orthorhombic space group Pbca and feature 1-D helical chains. These helical chains are linked to form a 2-D layer through pi-pi stacking interactions, which are further linked by hydrogen bonds to form a 3-D network. Solid-state properties such as thermal stability and fluorescence emission of the polymeric Zn complex 3 have also been investigated.