1. Department of Chemistry The University of Tokyo JST ERATO, Isobe Degenerate π-Integration Project Hongo, Bunkyo-ku Tokyo 113-0033 Japan
2. Present address: Institute of Molecular Plus Tianjin University No. 11 Building, No. 92 Weijin Road, Nankai District Tianjin 300072 P. R. China
3. Department of Chemistry Tohoku University Aoba-ku Sendai 980-8578 Japan