1. Department of Chemistry and Department of Energetic, University of Florence, Via Maragliano 75/77, 50144 Florence, Italy, Research and Development Division, Bracco SpA, Via Folli 50, 20134 Milano, Italy, Institute of Chemical Sciences, University of Urbino, Piazza Rinascimento 6, 61029 Urbino, Italy, and Department of Chemistry, University of Calabria, Arcavata di Rende, Italy