1. Department of Chemistry The University of Tokyo, Hongo Tokyo 113-0033 Japan
2. JST ERATO Isobe Degenerate π-Integration Project, Hongo Tokyo 113-0033 Japan
3. Advanced Institute for Materials Research Tohoku University Aoba-ku Sendai 980-8578 Japan
4. Present address: National Institute of Technology Sasebo College, Okishin-cho Sasebo 857-1193 Japan
5. Present address: Manipal Centre for Natural Sciences, Madhav Nagar Manipal 576104 Karnataka India