1. Dpto. Química Física y Analítica, Universidad de Oviedo, C/Julián Clavería, 8, 33006 (Oviedo) Asturias, Spain, 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, and Department of Physical Chemistry, Palacky University, 771 42 Olomouc, Czech Republic