1. Contribution from the Department of Chemistry, University of Colorado at Denver, Campus Box 194, P.O. Box 173364, Denver, Colorado 80217-3364, Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, and Department of Chemistry, Faculty of Science, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan