1. Contribution from the La.M.M., Department of Chemistry and INSTM Research Unit, Università di Firenze, Via della Lastruccia 3, 50019, Sesto Fiorentino (FI), Italy, and Sciences Chimiques de Rennes, UMR 6226 CNRS-INSA Rennes, Equipe “Matériaux Inorganiques: Chimie Douce et Réactivité”, INSA Rennes, 20 Avenue des buttes de Coësmes, CS 14315, 35043 Rennes Cedex, France