1. Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei, Taiwan 106, R.O.C.; Department of Chemistry, National Kaohsiung Normal University, Kaohsiung, Taiwan, R.O.C.; Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, R.O.C.; Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona, 85287-1604; and Japan Advanced Institute of Science and Technology, Tatsunokuchi, Ishikawa 923-12, Japan