1. Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1‐1‐1 Tennodai, Tsukuba, Ibaraki 305‐8577, Japan, Fax: +81‐29‐853‐4426
2. Department of Chemistry, Faculty of Science, Kyushu University, 6‐10‐1 Hakozaki, Higashi‐ku, Fukuoka 812‐8581, Japan, Fax: +81‐92‐642‐2507
3. Rigaku Corporation, 3‐9‐12 Mastubata‐cho, Akishima, Tokyo 196‐8666, Japan
4. Current address: JASRI, Kouto, Sayo‐cho, Sayo‐gun, Hyogo 679‐5198, Japan
5. RIKEN Spring‐8 Center, Kouto, Sayo‐cho, Sayo‐gun, Hyogo 679‐5198, Japan