1. Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, U.K.
2. Department
of Chemistry, University of Jyväskylä, P.O.Box 35, FI-40014 Jyväskylä, Finland
3. Departamento
de Química e Bioquímica, CQB, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisbon, Portugal