Co(II), Ni(II) and Cu(II) mononuclear and polynuclear complexes influenced by the aliphatic spacer length of their O 2N 2O 2 Schiff bases

Abstract

M(H 2L n )(H 2O) x and [M 2(L n )(H 2O) x ] n have been obtained by the electrochemical reaction of Co, Ni and Cu anodes with the O 2N 2O 2 symmetrical ligands: N, N′-bis(3-hydroxysalicylidene)-1,2-diaminopropane, H 4L 1, N, N′-bis(3-hydroxysalicylidene)-1,3-diaminopropane, H 4L 2, and N, N′-bis(3-hydroxysalicylidene)-1,4-diaminobutane, H 4L 3. The preferential attainment of mono- or polynuclear compounds seems to be conditioned by the aliphatic spacer length, among other factors. Spectroscopic and magnetic data suggest a distorted tetrahedral array in mono- and polynuclear nickel complexes with H 4L 2 and H 4L 3. However, when the aliphatic spacer is shorter, as occurs in Ni(H 2L 1), physicochemical data are consistent with a square planar geometry. The EPR data for polynuclear copper complexes display the characteristics of quasi-axial symmetry and show spin–spin interactions. Magnetic and electronic data point to high-spin distorted octahedral environments for Co(II) ions in [Co 2(L 3)(H 2O) 4] n .