1. a Department of Chemistry , University College of Science, University of Calcutta , 92, A.P.C. Road, Kolkata-700 009, India
2. b Bolpur College , Pin-731204, Bolpur, Birbhum, West Bengal, India
3. c IMEM-CNR , Parceo Area delle scienze 37a, I-43100 Fontanini, Parma, Italy