Carboxylate-bridged copper(II) complexes: synthesis, crystal structures, and superoxide dismutase activity

Abstract

Two copper(II) complexes, [Cu₂(μ-benzoato)(L¹)₂]NO₃·2H₂O (1) and [Cu₂(μ-succinato)(L²)₂(H₂O)]ClO₄ (2), have been synthesized, where L¹ = N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzoylhydrazone and L² = N′-[(E)-pyridin-2-ylmethylidene]benzoylhydrazone. These complexes were characterized including by single-crystal X-ray diffraction studies. The copper is five-coordinate in 1 while in 2 one copper is five-coordinate and the other is six-coordinate. Electrochemical behavior of these complexes was measured by cyclic voltammetry. The conproportionation equilibrium constants (K_con) for both complexes have been estimated. The superoxide dismutase (SOD) activities of 1 and 2 were measured by nitro blue tetrazolium assay. Complex 1 has better SOD activity than 2.

Keywords:

• Carboxylate-bridged copper(II)
• Crystal structure
• EPR spectra
• SOD activity

Acknowledgements

Our grateful thanks to School of Chemistry, University of Hyderabad, Hyderabad for Single Crystal X-ray data collection, RSIC (SAIF) IIT, Bombay for EPR measurements and SAIF, Central Drug Research Institute, Lucknow for providing elemental and IR spectral analysis. Financial assistance from CSIR, New Delhi [Scheme No. 01 (2451)/11/EMR-II] and MPCST, Bhopal [Project No. 5986/CST/R&D/2012] is also thankfully acknowledged.