We use native vibrational modes of the model singlet fission chromophore 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn) to examine the origins of singlet fission in solution between molecules that are not tethered by a covalent linkage. We use the C-H stretch modes of TIPS side groups of TIPS-Pn to demonstrate that singlet fission does not occur by diffusive encounter of independent molecules in solution. Instead, TIPS-Pn molecules aggregate in solution through their TIPS side groups. This aggregation breaks the symmetry of the TIPS-Pn molecules and enables the formation of triplets to be probed through the formally symmetry forbidden symmetric alkyne stretch mode of the TIPS side groups. The alkyne stretch modes of TIPS-Pn are sensitive to the electronic excited states present during the singlet fission reaction and provide unique signatures of the formation of triplets following the initial separation of triplet pair intermediates. These findings highlight the opportunity to leverage structural information from vibrational modes to better understand intermolecular interactions that lead to singlet fission.
|Journal||Journal of Chemical Physics|
|State||Published - Oct 21 2019|
Bibliographical noteFunding Information:
C.G., G.S.D., and J.B.A. thank the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences for support of this research through Grant No. DE-SC0019349. K.T.M. is grateful for support from the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1255832. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. I.D. acknowledges support from the Soltis faculty support award and the Ralph E. Powe junior faculty award from Oak Ridge Associated Universities. J.E.A. thanks the National Science Foundation (Grant No. CMMI-1255494) for supporting semiconductor synthesis.
© 2019 Author(s).
ASJC Scopus subject areas
- Physics and Astronomy (all)
- Physical and Theoretical Chemistry