1. Department of Chemistry, University of Sassari, Via Vienna 2, 07100 Sassari, Italy, Fax: +39‐79‐212069
2. Department of Inorganic and Analytical Chemistry, University of Debrecen, 4010 Debrecen, Hungary
3. Istituto C.N.R. di Chimica Biomolecolare Trav. La Crucca 3, 07040 Li Punti, Sassari, Italy