1. Contribution from SIRCOB, UMR CNRS 8086, Bât. Lavoisier, University of Versailles, F-78035 Versailles, France, Institute of Biomolecular Chemistry, CNR, Department of Chemistry, University of Padova, I-35131 Padova, Italy, and Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607-7061