Synthesis, Spectral, and Cyclic Voltammetric Studies of Tetraaza Copper(II), Oxovanadium(IV), and Zinc(II) Complexes Derived from 1,2‐(Diimino‐4′‐antipyrinyl)‐1,2‐diphenylethane and para‐Substituted Anilines

Abstract

Tetraaza acyclic Schiff bases, prepared from 1,2‐(diimino‐4′‐antipyrinyl)‐1,2‐diphenylethane and p‐substituted anilines, act as tetradentate ligands and form solid cationic solid complexes with Cu(II), Zn(II), and VO(IV) salts in ethanol. Microanalytical data, magnetic susceptibility measurements, IR, UV‐VIS, mass, ¹H and ¹³C NMR, and ESR spectral techniques were used to characterize the structures of synthesized compounds. IR and UV‐VIS spectra of the complexes suggest that all the copper complexes exhibit square–planar geometry while the oxovanadium complexes are of square–pyramidal geometry. Mass, ¹H and ¹³C NMR spectra of the Schiff bases and their complexes suggest that the general formula of the complexes is [ML]Y (where L = L¹, L² or L³, Y = Cl₂ or SO₄). Electrolytic behaviour of the chelates was assessed from their higher conductance data. Monomeric nature of the chelates was confirmed from their magnetic susceptibility values. Redox studies by cyclic voltammetry of copper complexes in MeCN suggest the existence of unusual oxidation states such as Cu(III), Cu(I), and Cu(0) which are stabilized by the ligand systems. The cyclic voltammogram of the oxovanadium complexes in MeCN shows two quasi‐reversible peak for the VO(IV)/VO(V) and VO(IV)/VO(III) couples. The X‐band ESR spectra of copper and oxovanadium complexes in DMSO solution at 300 and 77 K were recorded and their salient features are discussed.

Keywords:

• Tetraaza complexes
• Schiff base
• Oxovanadium complex
• p‐Substituted aniline complexes

Acknowledgments

The authors express their sincere thanks to the Managing Board, Principal and Head of the Department of Chemistry of Virudhunagar Hindu Nadars' Senthil Kumar Nadar College for providing research facilities. One of the authors (AK) thanks the Council of Scientific and Industrial Research, New Delhi for senior research fellowship award and he also thanks the Managing Board and Principal of SNS College of Technology for their encouragements.