1. Academy of Chinese Medicine Sciences, Henan University of Chinese Medicine, Zhengzhou, 450046, P. R. China
2. College of Chemistry and Chemical Engineering, Yan'an University, Yan'an, 716000, P. R. China
3. Lab of Theoretical Molecular Magnetism (LTMM), College of Chemistry and Materials Science, Northwest University, Xi'an, 710127, P. R. China