1. Contribution from the Department of Chemistry, University of Massachusetts at Boston, 100 Morrissey Blvd, Boston, Massachusetts, 02125-3393, Institute for Chemical Reaction Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-77, Japan, and Radio Isotope Center, Fukushima Medical College, 1 Hikarigaoka, Fukushima-shi, 960-12, Japan