1. Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bd. Regina Elisabeta, No. 4-12, Bucharest, Romania, Institute of Physical Chemistry “I. G. Murgulescu”, Splaiul Independentei, No. 202, 77208 Bucharest, Romania, and Department of Organic Chemistry, Faculty of Chemistry, University of Bucharest, Sos. Panduri, No. 90-92, Bucharest, Romania