1. Department of Chemical Industry and Chemistry, Weifang University, Weifang 261061, China, Fax: +86‐536‐8785283
2. Department of Chemistry, Graduate School of Science Tohoku University, Sendai 980‐8578, Japan
3. Department of Chemistry, Shandong University, Jinan 250100, China
4. Department of Physical Chemistry, Graduate School of Pharmaceutical Science Chiba University, Inage‐Yayoi, Chiba 263‐8522, Japan