Homoleptic coordination polymers and complexes of transition metals with 2-(1,2,4-1H-triazol-3-yl) pyridine and tuning towards white-light emission

Abstract

Twelve coordination compounds ranging from polymers to complexes based on divalent ions of the 3d-transition metals Mn to Zn, and Cd together with the ligand 2-(1,2,4-1H-triazol-3-yl)pyridine (Hpt) were synthesised and fully characterised. The main products are homoleptic, one-dimensional coordination polymers ¹_∞[M(pt)₂] (M = Mn–Zn, and Cd, pt = 3-(pyridin-2-yl)-1,2,4-triazolate), ¹_∞[Cu(pt)₂]·0.5Py, besides complexes [MX₂(Hpt)₂] from MnCl₂, FeCl₂, CoCl₂, CoBr₂, ZnCl₂, and Hpt = 2-(1,2,4-1H-triazol-3-yl)pyridine. In addition to these series, single crystalline by-products of the reactions were identified and their structures determined. The obtained products were investigated with single-crystal (SCXRD) and powder X-ray diffraction (PXRD), including temperature-dependent PXRD, physisorption experiments, UV-Vis, IR, and photoluminescence spectroscopy (PL), simultaneous thermal analysis, and elemental analysis. Based on ¹_∞[Zn(pt)₂], it was possible to generate a white light-emitting compound by addition of Eu³⁺ and Tb³⁺. It follows the RGB concept with blue ligand-based emission of the coordination polymer and red/green emission of lanthanide ions and shows excitation dependent tuneable character of emission colour from blue to practically perfect white.