1. Department of Chemistry, Faculty of Science, Okayama University of Science, Ridaicho, Okayama 700-0005, Japan, Advanced Materials Institute and Department of Chemistry, Faculty of Science, Fukuoka University, Nanakuma, Jyonan-ku, Fukuoka 814-0180, Japan, and Laboratoire Léon Brillouin, CEA-CNRS Saclay, 91191 Gif-sur-Yvette Cedex, France