Monovalent copper complexes of N-aryl-pyridine-2-aldimine. Synthesis, characterization and structure

Abstract

A direct synthetic route, based on silver(I) assisted metal exchange reaction, to cationic bis-ligand complexes of copper(I) involving N-aryl-pyridine-2-aldimines (L, 1) has been studied. These complexes are obtained as their perchlorates, [Cu(L)₂]ClO₄ (2). They have been characterized with the help of spectroscopy and X-ray crystallography. The X-ray structure of [Cu(L²)₂]ClO₄, where L² is N-p-tolyl-pyridine-2-aldimine is reported. There are two crystallographically independent molecules in the asymmetric unit. The ligand L² coordinates in a bidentate manner providing a highly distorted tetrahedral geometry about copper. The complexes show highly resolved symmetrical ¹H NMR spectra. Intense MLCT absorptions are observed in the visible range. In methanol the CuL₂²⁺/CuL₂⁺ couple has E_½ ca, 0.35 V vs SCE at 298 K. The moderately high positive potential is brought about by the distortion in the geometry of CuL₂²⁺.