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

Coordination polymers constructed from conjugated organic ligands and metal ions with a d electronic configuration exhibit intriguing properties for chemical sensing and photochemistry. A Zn-based coordination polymer, namely poly[aqua(μ-biphenyl-3,3',5,5'-tetracarboxylato)(μ-4,4'-bipyridine)dizinc(II)], [Zn(CHO)(CHN)(HO)] or [Zn(m,m-bpta)(4,4'-bipy)(HO)], was synthesized from a mixture of biphenyl-3,3',5,5'-tetracarboxylic acid [H(m,m-bpta)], 4,4'-bipyridine (4,4'-bipy) and Zn(NO)·6HO 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 μ-coordination mode. The Zn ions adopt square-pyramidal geometries and are bridged by two syn-syn carboxylate groups to form [Zn(COO)] secondary buildding units (SBUs). The SBUs are crosslinked by (m,m-bpta) 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 {4.6.8}{4.6} 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 Fe ions.