1. Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki-Aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan, X-ray Research Laboratory, Rigaku Co. Ltd., 3-9-12 Matsubara-cho, Akishima, Tokyo 196-8666, Japan, Department of Physics, Graduate School of Science, Tohoku University, 6-3 Aramaki-Aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan, and Department of Chemistry, Texas A&M University, PO Box 30012, College Station, Texas 77842-3012