1. Department of Applied Chemistry, Anhui University of Technology, Ma'anshan, Anhui 243002, P. R. China, Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China, Institut für Anorganische Chemie, Universität Karlsruhe (TH), 76128 Karlsruhe, Germany, and Department of Physics, Harbin Institute of Technology, Harbin 150001, P. R. China