1. Division of Material Science, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan
2. Molecular Device Laboratory, Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan
3. Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku Sendai 980-77, Japan
4. Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409