TY - JOUR
T1 - Geometries and Terahertz Motions Driving Quintet Multiexcitons and Ultimate Triplet-Triplet Dissociations via the Intramolecular Singlet Fissions
AU - Kobori, Yasuhiro
AU - Fuki, Masaaki
AU - Nakamura, Shunta
AU - Hasobe, Taku
N1 - Funding Information:
The work was supported by a Grant-in-Aid for Scientific Research (Nos. JP 19H00888, 17K19105, 20K21174 to Y.K., and 18H01957 to T.H.) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Y.K. appreciates fruitful discussions with Prof. Kazuyuki Ishii (The University of Tokyo) and with Prof. Tomoaki Yago (Saitama University) on the importance of the H interaction included in the spectrum computations. This work was carried out by the joint research program of Molecular Photoscience Research Center, Kobe University. TTss
Publisher Copyright:
© 2020 American Chemical Society.
PY - 2020/10/22
Y1 - 2020/10/22
N2 - Importance of vibronic effects has been highlighted for the singlet-fission (SF) that converts one high-energy singlet exciton into doubled triplet excitons, as strongly coupled multiexcitons. However, molecular mechanisms of spin conversion processes and ultimate decouplings in the multiexcitons are poorly understood. We have analyzed geometries and exchange couplings (singlet-quintet energy gaps: 6J) of the photoinduced multiexcitons in the pentacene dimers bridged by a phenylene at ortho and meta positions [denoted as o-(Pc)2 and m-(Pc)2] by simulations of the time-resolved electron paramagnetic resonance spectra. We clarified that terahertz molecular conformation dynamics play roles on the spin conversion from the singlet strongly coupled multiexcitons 1(TT) to the quintet multiexcitons 5(TT) and on the intramolecular decouplings in the 6J to form spin correlated triplet pairs (T+T). The strongly coupled 5(TT) multiexcitons are revealed to possess entirely planar conformations stabilized by mutually delocalized spin distributions, while the intramolecular decoupled spin-correlated triplet pairs generated at 1 μs are also stabilized by distorted conformations resulting in two separately localized biradical characters.
AB - Importance of vibronic effects has been highlighted for the singlet-fission (SF) that converts one high-energy singlet exciton into doubled triplet excitons, as strongly coupled multiexcitons. However, molecular mechanisms of spin conversion processes and ultimate decouplings in the multiexcitons are poorly understood. We have analyzed geometries and exchange couplings (singlet-quintet energy gaps: 6J) of the photoinduced multiexcitons in the pentacene dimers bridged by a phenylene at ortho and meta positions [denoted as o-(Pc)2 and m-(Pc)2] by simulations of the time-resolved electron paramagnetic resonance spectra. We clarified that terahertz molecular conformation dynamics play roles on the spin conversion from the singlet strongly coupled multiexcitons 1(TT) to the quintet multiexcitons 5(TT) and on the intramolecular decouplings in the 6J to form spin correlated triplet pairs (T+T). The strongly coupled 5(TT) multiexcitons are revealed to possess entirely planar conformations stabilized by mutually delocalized spin distributions, while the intramolecular decoupled spin-correlated triplet pairs generated at 1 μs are also stabilized by distorted conformations resulting in two separately localized biradical characters.
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U2 - 10.1021/acs.jpcb.0c07984
DO - 10.1021/acs.jpcb.0c07984
M3 - Article
C2 - 32981315
AN - SCOPUS:85094221684
SN - 1520-6106
VL - 124
SP - 9411
EP - 9419
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 42
ER -