1. Department of Chemistry, Columbia University, New York, New York 10027, United States
2. Institute of Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
3. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
4. Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States