1. Laboratoire Francis Perrin, CEA/DSM/IRAMIS/SPAM - CNRS URA 2453, CEA/Saclay, 91191 Gif-sur-Yvette, France, Dpto. Química Física y Analítica, Universidad de Oviedo, C/ Julián Clavería, 8, 33006(Oviedo) Asturias, Spain, and Center for Biomolecules and Complex Molecular Systems, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 16610 Prague 6, Czech Republic