1. Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6; Department of Chemistry and Chemical Informatics, Faculty of Education, University of Szeged, Szeged, Boldogasszony sgt. 6, Hungary 6725; and Institute of Biocomputations and Physics of Complex Systems, Department of Theoretical Physics, University of Zaragoza, Zaragoza, Spain 50009