1. Department of Chemical Sciences, Via S. Agostino 1, University of Camerino, I-62032 Camerino (MC), Italy, Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal, Department of Chemistry “G. Ciamician”, University of Bologna, Via Selmi 2, I-40126 Bologna, Italy, and Department of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova, Italy