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

Abstract

Two novel zinc coordination polymers [Zn 2(H 2O)L(MoO 4)] n ( 1) and [Zn 4(PO 4) 2L′(H 2O)] n ( 2) (H 2L=2,2′-bipyridine-6.6′-dicarboxylic acid, H 2L′=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 [Zn 2L(H 2O)] 2+ units and MoO 4 2– groups whereas 2 displays an interesting 3-D framework constructed by tetranuclear zinc clusters, L′ 2− ligands and PO 4 3– 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 π–π⁎ transitions of H 2L and H 2L′ ligands and the ligand-to-metal-charge-transfer transitions.