Jahn–Teller distortion in 2-pyridyl-(1,2,3)-triazole-containing copper(ii) compounds

Abstract

The syntheses, characterization and experimental solid state X-ray structures of five low-spin paramagnetic 2-pyridyl-(1,2,3)-triazole-copper compounds, [Cu(Lⁿ)₂Cl₂], are presented in this study, for the following five Lⁿ ligands: L¹ = 2-(1-(p-tolyl)-1H-(1,2,3-triazol-4-yl)pyridine), L² = 2-(1-(4-chlorophenyl)-1H-(1,2,3-triazol-4-yl)pyridine), L³ = 4-(4-(pyridin-2-yl)-1H-(1,2,3-triazol-4-yl)benzonitril), L⁴ = 2-(1-phenyl-1H-(1,2,3-triazol-4-yl)pyridine) and L⁵ = 2-(1-(4-(trifluoromethyl)phenyl)-1H-(1,2,3-triazol-4-yl)pyridine). These five [Cu(Lⁿ)₂Cl₂] complexes each contain two bidentate 2-pyridyl-(1,2,3)-triazole (Lⁿ) and two chloride ions as ligands, with the Cu–N(pyridine) bonds, Cu–N(triazole) and Cu–Cl bonds trans to each other. All five [Cu(Lⁿ)₂Cl₂] compounds display elongation Jahn–Teller distortion, either along opposite Cu–N(triazole) bonds, or along opposite Cu–Cl bonds, as indicated by their obtained solid state crystal structures. Quantum chemistry calculations, using density functional theory, indicated however that elongation Jahn–Teller distortion is in fact possible along any two opposite bonds in these octahedral compounds with the elongation distortion along the opposite Cu–N(triazole) bonds being the most stable structure.