1. Department of Chemistry, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh
2. Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
3. Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, U.K.
4. Department of Chemistry I.F.M., University of Turin, via P. Giuria 7, 10125 Turin, Italy