1. Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K.
2. Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, U.K.
3. Technische Universität Berlin, Institut
für Chemie, Sekr. C7, Strasse des 17. Juni 135,
10623 Berlin, Germany
4. School of Chemistry and Biochemistry, University of Western Australia, 35 Stirling Highway, Crawley,
Perth 6009, Australia