1. Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700009, India
2. Chittaranjan National Cancer Institute, 37 S. P. Mukherjee Road, Kolkata 700026, India
3. Department of Chemistry, Maharaja Manindra Chandra College, Kolkata 700003, India
4. Dipartimento di Scienze Chimiche, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy