1. State Key Laboratory of Supramolecular Structure and Materials and College of Chemistry, Jilin University, Changchun 130012, P.R. China, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China, and Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, P.R. China