1. Department of Chemistry and Center for Laser and Photonics Research, Oklahoma State University, Stillwater, Oklahoma 74078; Facultad de Quñmica, Universidad Nacional Autónoma de Mexico, Coyoacan, Mexico D.F., 04510 Mexico; Facultad de Quñmica, University of Guanajuato, Noria Alta s/n, Guanajuato GTO, 36050 Mexico; and Instituto de Investigacion en Materiales, Universidad Nacional Autónoma de Mexico, Coyoacan, Mexico D.F., 04510 Mexico