Five Cu(I) and Zn(II) clusters and coordination polymers of 2-pyridyl-1,2,3-triazoles: synthesis, structures and luminescence properties

Three stair-step[Cu4I4] cluster-based complexes [Cu4I4(L1)(2)] (1), [Cu4I4(L-2)](n) (2) and [Cu4I4(L3)](n)center dot 2n(CH3CN) (3) and two linear Zn(II) coordination polymers [ZnCl2(L1)](n) (4) and [ZnCl2(L3)](n) (5) with 2-pyridyl-triazole ligands (L1 = 2-((4-propyl-1H-1,2,3-triazol-1-yl)methyl) pyridine, L2 = 1,3-bis(1-(pyridin-2-ylmethyl)-1H-1,2,3-triazol-4-yl) propane and L3 = 1,4-bis(1-(pyridin-2-ylmethyl)-1H-1,2,3-triazol-4-yl)butane) have been synthesized and characterized by single-crystal X-ray diffraction (XRD), powder XRD, thermogravimetric analysis and photoluminescence spectroscopy. Complex 1 possesses a stair-step [Cu4I4] cluster structure. Complexes 2 and 3 are 1-D polymeric forms of [Cu4I4] clusters. Complexes 4 and 5 are 1-D Zn(II) polymeric structures bridged by L1 and L3 spacers, respectively. In 1-3, ligands L1-L3 adopt a bidentate/monodentate dual coordination mode through the assistance of the triazole and pyridyl nitrogen donors. Ligand L1 exhibits an unusual open-bridging mode in complex 4, employing N-py and 3'-N-tri donors. By comparison, ligand L3 bridges two metal centers in complex 5 using 3,3'-N-tri donors. The structural (4-pyridyl- and 2-pyridyl-triazole) and H-bonding interaction effects on the coordination structures are described and discussed. All five complexes exhibit solid-state photoluminescence with maximum emission in the region of 440-490 nm.