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 RG 66AD, UK
3. Department of Engineering Science, The University of Electro‐Communications, Chofu, Tokyo 182‐8585, Japan