Jahn-Teller distortion in 2-pyridyl-(1,2,3)-triazolecontaining copper(II) compounds

The syntheses, characterization and experimental solid state X-ray structures of five low-spin paramagnetic 2-pyridyl-(1,2,3)-triazole-copper compounds, [Cu(L-n)(2)Cl-2], are presented in this study, for the following five L-n ligands: L-1 = 2-(1-(p-tolyl)-1H-(1,2,3-triazol-4-yl) pyridine), L-2 = 2-(1-(4chlorophenyl)-1H-(1,2,3-triazol-4-yl) pyridine), L-3 = 4-(4-(pyridin-2-yl)-1H-(1,2,3-triazol-4-yl)benzonitril), L-4 = 2-(1-phenyl-1H-(1,2,3-triazol-4-yl) pyridine) and L-5 = 2-(1-(4-(trifluoromethyl)phenyl)-1H-(1,2,3triazol-4-yl) pyridine). These five [Cu(L-n)(2)Cl-2] complexes each contain two bidentate 2-pyridyl-(1,2,3)triazole (L-n) 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(L-n)(2)Cl-2] 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.