1. School of Chemistry and Chemical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, P. R. China
2. Department of Chemistry, College of Sciences, King Saud University, Riyadh 11451, Saudi Arabia
3. Department of Science, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa, Yamagata 990-8560, Japan