1. Departamento de Quı́mica, Universidad de Guanajuato, Col. Noria Alta S/N, Guanajuato, Gto.
36050, Mexico
2. Departamento de Quı́mica Fı́sica, Universidad del Paı́s Vasco/EHU, Aptdo 644, 48080, Bilbao, Spain
3. Department of Chemistry, The University of Texas at El Paso, 500 West University Avenue, El
Paso, Texas 79968, United States