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

Abstract

Three stair-step [Cu₄I₄] cluster-based complexes [Cu₄I₄(L1)₂] (1), [Cu₄I₄(L2)]_n (2) and [Cu₄I₄(L3)]_n·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.