Two multi-dimensional frameworks constructed from zinc coordination polymers with pyridine carboxylic acids

Two novel zinc coordination polymers [Zn-2(H2O)L(MoO4)](n) (1) and [Zn-4(PO4)(2)L'(H2O)](n) (2) (H2L=2,2'-bipyridine-6.6'-dicarboxylic acid, H2L'=2,2'-bipyridine-4,4'-dicarboxylic acid) have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, UV spectra, single-crystal X-ray diffraction and thermogravimetric analyses. Structural analyses indicate that 1 represents a 2-D sheet structure built by dimeric [Zn2L(H2O)](2+) units and MoO42- groups whereas 2 displays an interesting 3-D framework constructed by tetranuclear zinc clusters, L'(2-) ligands and PO43- groups. Examination of UV spectra suggests that both 1 and 2 can stably exist in the pH range of 2.45-5.45 and 3.01-8.55 in aqueous solution, respectively. The room-temperature solid-state photoluminescence of 1 and 2 are derived from the intra-ligands pi-pi* transitions of H2L and H2L' ligands and the ligand-to-metal-charge-transfer transitions. (C) 2011 Elsevier Inc. All rights reserved.