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

Two novel zinc coordination polymers [Zn2(H2O)L(MoO4)]n (1) and [Zn4(PO4)2L′(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 π–π⁎ transitions of H2L and H2L′ ligands and the ligand-to-metal-charge-transfer transitions.

Graphical AbstractTwo new transition metal coordination polymers, namely, [Zn2(H2O)L1(MoO4)]n (1), [Zn4(PO4)2L2(H2O)]n (2) (H2L1=2,2′-bipyridine-6,6′-dicarboxylic acid, H2L2=2,2′-bipyridine-4,4′-dicarboxylic acid) have been hydrothermally synthesized. 1 represents a 2-D sheet structure while 2 represents 3-D network.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights►Two new transition metal coordination polymers have been hydrothermally synthesized. ► The two compounds have been characterized by elemental analyses, IR, UV spectra, single-crystal X-ray diffraction, thermogravimetric analyses and photoluminescence. ► Compound 1 represents a 2-D sheet structure while 2 represents 3-D network.