1. Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo‐ku, Kyoto 615‐8510, Japan, Fax: (+81) 75‐383‐2732
2. School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), Asahidai, Tatsunokuchi, Ishikawa 923‐1292, Japan