1. Department of Chemistry, University College of Science and Technology, University of Calcutta, 92, A. P. C. Road, 700 009 Kolkata, India
2. Centro di Studio per la Strutturistica Diffratometrica del CNR, 43100 Parma, Italy
3. R.S.I.C, Bose Institute, 700 009 Kolkata, India
4. Department of Chemistry, Washington State University, Pullman, WA 99164, USA
5. Instituto de Ciencia Molecular, Universidad de Valencia, Dr. Moliner 50, 46100 Burjasot (Valencia), Spain