1. Contribution from the Grenoble High Magnetic Field LaboratoryCNRS, 38042 Grenoble, France, Department of Chemistry & INSTM (UdR Firenze), University of Florence, Sesto Fiorentino, 50019, Italy, and Department of Chemistry & INSTM (UdR Modena), University of Modena and Reggio Emilia, Modena, 41100, Italy