Affiliation: | 1. State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P.?R. China;2. College of Chemistry & Materials Science, Shaanxi Normal University, Xian 710062, P.?R. China, (phone: +86‐931‐8912592;3. fax: +86‐931‐8912582) |