Co(II), Ni(II) and Cu(II) mononuclear and polynuclear complexes influenced by the aliphatic spacer length of their O2N2O2 Schiff bases

M(H2Ln)(H2O)x and [M2(Ln)(H2O)x]n have been obtained by the electrochemical reaction of Co, Ni and Cu anodes with the O2N2O2 symmetrical ligands: N,N′-bis(3-hydroxysalicylidene)-1,2-diaminopropane, H4L1, N,N′-bis(3-hydroxysalicylidene)-1,3-diaminopropane, H4L2, and N,N′-bis(3-hydroxysalicylidene)-1,4-diaminobutane, H4L3. 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 H4L2 and H4L3. However, when the aliphatic spacer is shorter, as occurs in Ni(H2L1), 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 [Co2(L3)(H2O)4]n.