1. a Department of Chemistry and Chemical Informatics, Faculty of Education , University of Szeged , H-6701 Szeged, P.O. Box 396, Hungary
2. b Department of Organic Chemistry , University of Szeged , H-6720 Szeged, Do´m te´r 8, Hungary
3. c Department of Chemistry , University of Toronto , 80 St. George St., Toronto, ON Canada, M5S 3H6