1. Department of Chemistry and Biochemistry San Diego State University 5500 Campanile Drive San Diego CA 92182‐1030 USA
2. College of Chemistry & Chemical Engineering Northeast Petroleum University Daqing 163318 P. R. China
3. Key Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education Department of Chemistry Tsinghua University Beijing 100084 P. R. China