[1] Univ Paris 11, CNRS, Inst Chim Mol & Mat Orsay, F-91405 Orsay, France
[2] CNRS INSA, UMR 6226, Equipe Mat Inorg Chim Douce & React, F-35043 Rennes, France
[3] Univ Paris 11, CNRS, UMR 8502, Lab Phys Solides, F-91405 Orsay, France
[4] Ecole Polytech Fed Lausanne, Lab Chim Supramol Lanthanides, BCH 1402, CH-1015 Lausanne, Switzerland