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

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, NO2 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·H2O, 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 μB. 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⊥g⊥ = 2.06–2.07, and A⊥(N)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.

Graphical abstractSyntheses, properties and structures of a series of copper(II) complexes having the formula [CuL(OAc)] (HL = n-R-2-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol (R = H, Br, NO2 and OMe when n = 4 and R = OMe when n = 5)) are reported. The metal center in these complexes is in irregular N2O3 coordination sphere assembled by the N,N,O-donor L− and the bidentate acetate. One of the complexes (R = Br) forms dimeric units due to a pair of reciprocal Cu⋯Br interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide