1. Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata-7000 032, India, Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, 1-8-4 Kanda Surugadai, Chiyoda-ku, Tokyo 101-8308, Japan, and Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan