1. Department of Chemistry, University College of Science, University of Calcutta, 92 A. P. C. Road, Kolkata 700009, India
2. School of Chemistry, The University of Reading, P. O. Box 224, Whiteknights, Reading RG6 6AD, UK
3. Departament de Química, Universitat de les Illes Balears, Crta. de Valldemossa km 7.5, 07122 Palma (Baleares), Spain