1. Department of Chemistry, University of Rome “La Sapienza”, P.le A. Moro 5, 00185 Rome, Italy, and Department “Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive”, University of Rome “La Sapienza”, P.le A. Moro 5, 00185 Rome, Italy, and Department of Physics, University of Rome “Roma Tre”, Via della Vasca Navale 84, 00146 Rome, Italy