Mixed ligand Cu(II) complexes containing o-vanillin-l-tryptophan Schiff base and heterocyclic nitrogen bases: synthesis, structural characterization, and biological properties

Abstract

[Cu(L)] (1) and mixed ligand copper(II) complexes [Cu(L)(A)] (2 and 3), where L is the Schiff base derived from o-vanillin and l-tryptophan and A is pyridine (2) and imidazole (3), were synthesized and characterized using conventional and spectral techniques. 2 was structurally characterized using single crystal X-ray crystallography showing that Cu(II) is coordinated through N₂O₂ donors in a square plane. The EPR spectra of the complexes in frozen solution support a square-based structure. Electrochemical behavior of the complexes has been studied by cyclic voltammetry. The DNA-binding properties of L and 1–3 with calf thymus DNA were investigated by spectral and kinetic methods. For all the complexes, the maximum value of binding constant (0.38 × 10⁶) was achieved with 3 by spectroscopic titration. The ability of compounds to break pUC19 DNA was checked by gel electrophoresis. The ligand and copper complexes exert cytotoxicity against MCF-7 cell line.

Keywords:

• Copper(II) complex
• Amino acid Schiff base
• Crystal structure
• Spectroscopy
• DNA binding and cleavage

Acknowledgements

Council of Scientific and Industrial Research (CSIR), New Delhi, India [01(2736)/13/EMR-II] is gratefully acknowledged for financial support. One of the authors (C.B.) thanks CSIR for the fellowship. We thank Dr B.S. Lakshmi, Centre for Biotechnology, Anna University, Chennai for cytotoxicity studies. Authors thank SAIF, Mumbai for EPR spectra and STIC, Cochin for single crystal XRD and NMR spectra.