1. Department of Chemical Sciences, University of Padua, via Marzolo 1, 35131 Padua, Italy, Clinical and Experimental Hematology Research Unit, C.R.O. Research Area, I.R.C.C.S., via Pedemontana Occ.le 12, I-33081 Aviano (PN), Italy, and Institute of Inorganic and Surfaces Chemistry, C.N.R. Research Area, corso Stati Uniti 4, 35127 Padua, Italy