Preparation, characterisation and redox properties of four new tetradentate salicylaldimines with their Cu(II) complexes

Some new tetradentate salicylaldimine ligands of Schiff bases were synthesised by treating 3,5-di-tertbutyl-2-hydroxybenzaldehyde with 1,2-bis-(o-aminophenoxy)ethane, 1,4-bis-(o-aminophenoxy)butane, 1,4-bis(m-aminophenoxy)buthane and 1,4-bis-(p-aminophenoxy)butane. The compounds were characterised by IR, UV-vis, H-1 NMR, C-13 NMR, magnetic susceptibility measurements, elemental analysis, molar conductance (Am), thermogravimetric analysis (TGA) and cyclic voltammetry. The metal to ligand ratios of the Cu(II) complexes were found to be 1:1. The coordination of the novel tetradentate salicylaldimines appears to occur through the two azomethine nitrogens and two o-OH groups. Cyclic voltammetric studies showed that all of the C(II) complexes undergo quasi reversible one-electron transfer redox processes attributed the Cu(II)/Cu(I) couples in dimethylsufoxide. The electron donor affinity of copper(II) complexes increases in order Cu(L-4)>Cu(L-3)>Cu(L-2)>Cu(L-1).