1. Department of Chemistry “G. Ciamician”, University of Bologna, Via Selmi 2, I-40126 Bologna, Italy, Department of Chemical Sciences, University of Catania, Viale A. Doria 6, I-95125 Catania, Italy, and Department of Clinical Medicine, Prevention and Biotechnology, University of Milano-Bicocca, Via Cadore 48, I-20052 Monza, Italy