1. Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
2. College of Chemistry and Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, Xiangtan University, Xiangtan 411105, P. R. China
3. Departement für Chemie, Universität Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland