Synthesis, structure and selective luminescence sensing for iron(III) ions of a three-dimensional zinc(II) (4,6)-connected coordination network

Abstract

Coordination polymers constructed from conjugated organic ligands and metal ions with a d 10 electronic configuration exhibit intriguing properties for chemical sensing and photochemistry. A ZnII-based coordination polymer, namely poly[aqua(μ6-biphenyl-3,3′,5,5′-tetracarboxylato)(μ2-4,4′-bipyridine)dizinc(II)], [Zn2(C16H6O8)(C10H8N2)(H2O)2] n or [Zn2(m,m-bpta)(4,4′-bipy)(H2O)2] n , was synthesized from a mixture of biphenyl-3,3′,5,5′-tetracarboxylic acid [H4(m,m-bpta)], 4,4′-bipyridine (4,4′-bipy) and Zn(NO3)2·6H2O under solvothermal conditions. The title complex has been structurally characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction and powder X-ray diffraction analysis, and features a μ6-coordination mode. The ZnII ions adopt square-pyramidal geometries and are bridged by two syn–syn carboxylate groups to form [Zn2(COO)2] secondary buildding units (SBUs). The SBUs are crosslinked by (m,m-bpta)4− ligands to produce a two-dimensional grid-like layer that exhibits a stair-like structure along the a axis. Adjacent layers are linked by 4,4′-bipy ligands to form a three-dimensional network with a {44.610.8}{44.62} topology. In the solid state, the complex displays a strong photoluminescence and an excellent solvent stability. In addition, the luminescence sensing results indicate a highly selective and sensitive sensing for Fe3+ ions.