Copper(II) complexes with 2-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol and its substituted derivatives: Syntheses, physical properties and structures

Abstract

Five new complexes of copper(II) having the general formula [CuL(OAc)], where HL and OAc − represent the N,N,O-donor 4- R-2-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol ( R = H, Br, NO 2 and OMe) or 5-methoxy-2-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol and acetate, respectively have been reported. The complexes have been synthesized in 52–80% yields by reacting one mole equivalent each of Cu(OAc) 2·H 2O, 2-(2-aminoethyl)pyridine and the appropriate substituted salicylaldehyde in methanol. The solid state effective magnetic moments of the complexes at 298 K are within 1.79–1.97 μ B. In solution, all the complexes are electrically non-conducting. The electronic spectra of these species display a weak ligand-field band within 640–615 nm and several strong charge transfer bands in the range 410–235 nm. The complexes are EPR active. The frozen (120 K) solution spectral parameters are g || = 2.22–2.23, A || = 189–191 × 10 −4 cm −1, g ⊥ = 2.06–2.07, and A ⊥ ( N ) = 10–16 × 10 −4 cm −1. X-ray structures show that the ligand L − coordinates the metal center through the phenolate-O, the imine-N and the pyridine-N and forms two six-membered chelate rings. The acetate is bidentate but asymmetric with respect to the Cu–O as well as C–O bond lengths. Only the complex where R = Br dimerises due to two reciprocal Cu⋯Br interactions.