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-tert-butyl-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, ¹H NMR, ¹³C NMR, magnetic susceptibility measurements, elemental analysis, molar conductance (Λ_M), 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 Cu(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(L₄)>Cu(L₃)>Cu(L₂)>Cu(L₁).