1. Department of Chemistry, Korea University, Chung-nam 339-700, Korea, Fuel Cell Center, Korea Institute of Science and Technology, Hawolgok-dong 39-1, Seongbuk-gu, Seoul 136-791, Korea, Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, R. Ingardena 3, 30-060 Kraków, Poland, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA