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Title: 1,3-Diphenylisobenzofuran: a Model Chromophore for Singlet Fission

Abstract

In this review we first provide an introductory description of the singlet fission phenomenon and then describe the ground and electronically excited states of the parent 1,3-diphenylisobenzofuran chromophore (1) and about a dozen of its derivatives. A discussion of singlet fission in thin polycrystalline layers of these materials follows. The highest quantum yield of triplet formation by singlet fission, 200% at 80 K, is found in one of the two known crystal modification of the parent. In the other modification and in many derivatives, excimer formation competes successfully and triplet yields are low. A description of solution photophysics of covalent dimers is described in the next section. Triplet yields are very low, but interesting phenomena are uncovered. One is an observation of a separated-charges (charge-transfer) intermediate in highly polar solvents. The other is an observation of excitation isomerism in both singlet and triplet states, where in one isomer the excitation is delocalized over both halves of the covalent dimer, whereas in the other it is localized on one of the halves. Finally, in the last section we present the operation of a simple device illustrating the use of triplets generated by singlet fission for charge separation.

Authors:
ORCiD logo [1]; ORCiD logo [2]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Univ. of Colorado, Boulder, CO (United States). Dept. of Chemistry and Biochemistry; Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic). Inst. of Organic Chemistry and Biochemistry
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1394736
Report Number(s):
NREL/JA-5900-68011
Journal ID: ISSN 2365-0869
Grant/Contract Number:
AC36-08GO28308; SC0007004; GA15-19143S
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Topics in Current Chemistry
Additional Journal Information:
Journal Volume: 375; Journal Issue: 5; Journal ID: ISSN 2365-0869
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; 1,3-diphenylisobenzofuran; photophysics; solar energy; singlet fission; covalent dimers

Citation Formats

Johnson, Justin C., and Michl, Josef. 1,3-Diphenylisobenzofuran: a Model Chromophore for Singlet Fission. United States: N. p., 2017. Web. doi:10.1007/s41061-017-0162-3.
Johnson, Justin C., & Michl, Josef. 1,3-Diphenylisobenzofuran: a Model Chromophore for Singlet Fission. United States. doi:10.1007/s41061-017-0162-3.
Johnson, Justin C., and Michl, Josef. 2017. "1,3-Diphenylisobenzofuran: a Model Chromophore for Singlet Fission". United States. doi:10.1007/s41061-017-0162-3.
@article{osti_1394736,
title = {1,3-Diphenylisobenzofuran: a Model Chromophore for Singlet Fission},
author = {Johnson, Justin C. and Michl, Josef},
abstractNote = {In this review we first provide an introductory description of the singlet fission phenomenon and then describe the ground and electronically excited states of the parent 1,3-diphenylisobenzofuran chromophore (1) and about a dozen of its derivatives. A discussion of singlet fission in thin polycrystalline layers of these materials follows. The highest quantum yield of triplet formation by singlet fission, 200% at 80 K, is found in one of the two known crystal modification of the parent. In the other modification and in many derivatives, excimer formation competes successfully and triplet yields are low. A description of solution photophysics of covalent dimers is described in the next section. Triplet yields are very low, but interesting phenomena are uncovered. One is an observation of a separated-charges (charge-transfer) intermediate in highly polar solvents. The other is an observation of excitation isomerism in both singlet and triplet states, where in one isomer the excitation is delocalized over both halves of the covalent dimer, whereas in the other it is localized on one of the halves. Finally, in the last section we present the operation of a simple device illustrating the use of triplets generated by singlet fission for charge separation.},
doi = {10.1007/s41061-017-0162-3},
journal = {Topics in Current Chemistry},
number = 5,
volume = 375,
place = {United States},
year = 2017,
month = 9
}

Journal Article:
Free Publicly Available Full Text
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  • Single crystal molecular structure and solution photophysical properties are reported for 1,3-diphenylisobenzofuran (1), of interest as a model compound in studies of singlet fission. For the ground state of 1 and of its radical cation (1{sup +{sm_bullet}}) and anion (1{sup -{sm_bullet}}), we report the UV-visible absorption spectra, and for neutral 1, also the magnetic circular dichroism (MCD) and the decomposition of the absorption spectrum into purely polarized components, deduced from fluorescence polarization. These results were used to identify a series of singlet excited states. For the first excited singlet and triplet states of 1, the transient visible absorption spectra, S{submore » 1} {yields} S{sub x} and sensitized T{sub 1} {yields} T{sub x}, and single exponential lifetimes, {tau}{sub F} = {approx} 5.3 ns and {tau}{sub T} = {approx}200 {mu}s, are reported. The spectra and lifetimes of S{sub 1} {yields} S{sub 0} fluorescence and sensitized T{sub 1} {yields} T{sub x} absorption of 1 were obtained in a series of solvents, as was the fluorescence quantum yield, {Phi}{sub F} = 0.95-0.99. No phosphorescence has been detected. The first triplet excitation energy of solid 1 (11,400 cm{sup -1}) was obtained by electron energy loss spectroscopy, in agreement with previously reported solution values. The fluorescence excitation spectrum suggests an onset of a nonradiative channel at {approx} 37,000 cm{sup -1}. Excitation energies and relative transition intensities are in agreement with those of ab initio (CC2) calculations after an empirical 3000 cm{sup -1} adjustment of the initial state energy to correct differentially for a better quality description of the initial relative to the terminal state of an absorption transition. The interpretation of the MCD spectrum used the semiempirical PPP method, whose results for the S{sub 0} {yields} S{sub x} spectrum require no empirical adjustment and are otherwise nearly identical with the CC2 results in all respects including the detailed nature of the electronic excitation. The ground state geometry of 1 was also calculated by the MP2, B3LYP, and CAS methods. The calculations provided a prediction of changes of molecular geometry upon excitation or ionization and permitted an interpretation of the spectra in terms of molecular orbitals involved. Computations suggest that 1 can exist as two nearly isoenergetic conformers of C{sub 2} or C{sub s} symmetry. Linear dichroism measurements in stretched polyethylene provide evidence for their existence and show that they orient to different degrees, permitting a separation of their spectra in the region of the purely polarized first absorption band. Their excitation energies are nearly identical, but the Franck-Condon envelopes of their first transition differ to a surprising degree.« less