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Title: Chain Length Dependence of Energies of Electron and Triplet Polarons in Oligofluorenes

Bimolecular equilibria measured the one-electron reduction potentials and triplet free energies (ΔG° T) of oligo(9,9-dihexyl)fluorenes and a polymer with lengths of n = 1–10 and 57 repeat units. We can accurately measure one-electron potentials electrochemically only for the shorter oligomers. Starting at n = 1 the free energies change rapidly with increasing length and become constant for lengths longer than the delocalization length. Both the reduction potentials and triplet energies can be understood as the sum of a free energy for a fixed polaron and a positional entropy. Furthermore, the positional entropy increases gradually with length beyond the delocalization length due to the possible occupation sites of the charge or the triplet exciton. Our results reinforce the view that charges and triplet excitons in conjugated chains exist as polarons and find that positional entropy can replace a popular empirical model of the energetics.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ; ORCiD logo [4] ; ORCiD logo [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Dept.
  2. Thammasat Univ., Pathum Thani (Thailand). Sirindhorn International Inst. of Technology
  3. Kyoto Inst. of Technology, Sakyo-ku (Japan). Faculty of Materials Science and Engineering
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). Center of Functional Nanomaterials
Publication Date:
Report Number(s):
BNL-113668-2017-JA
Journal ID: ISSN 1932-7447; R&D Project: CO004; KC0304030
Grant/Contract Number:
SC00112704; AC02-98-CH10886
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 121; Journal Issue: 11; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1349560

Chen, Hung Cheng, Sreearunothai, Paiboon, Cook, Andrew R., Asaoka, Sadayuki, Wu, Qin, and Miller, John R.. Chain Length Dependence of Energies of Electron and Triplet Polarons in Oligofluorenes. United States: N. p., Web. doi:10.1021/acs.jpcc.7b00099.
Chen, Hung Cheng, Sreearunothai, Paiboon, Cook, Andrew R., Asaoka, Sadayuki, Wu, Qin, & Miller, John R.. Chain Length Dependence of Energies of Electron and Triplet Polarons in Oligofluorenes. United States. doi:10.1021/acs.jpcc.7b00099.
Chen, Hung Cheng, Sreearunothai, Paiboon, Cook, Andrew R., Asaoka, Sadayuki, Wu, Qin, and Miller, John R.. 2017. "Chain Length Dependence of Energies of Electron and Triplet Polarons in Oligofluorenes". United States. doi:10.1021/acs.jpcc.7b00099. https://www.osti.gov/servlets/purl/1349560.
@article{osti_1349560,
title = {Chain Length Dependence of Energies of Electron and Triplet Polarons in Oligofluorenes},
author = {Chen, Hung Cheng and Sreearunothai, Paiboon and Cook, Andrew R. and Asaoka, Sadayuki and Wu, Qin and Miller, John R.},
abstractNote = {Bimolecular equilibria measured the one-electron reduction potentials and triplet free energies (ΔG°T) of oligo(9,9-dihexyl)fluorenes and a polymer with lengths of n = 1–10 and 57 repeat units. We can accurately measure one-electron potentials electrochemically only for the shorter oligomers. Starting at n = 1 the free energies change rapidly with increasing length and become constant for lengths longer than the delocalization length. Both the reduction potentials and triplet energies can be understood as the sum of a free energy for a fixed polaron and a positional entropy. Furthermore, the positional entropy increases gradually with length beyond the delocalization length due to the possible occupation sites of the charge or the triplet exciton. Our results reinforce the view that charges and triplet excitons in conjugated chains exist as polarons and find that positional entropy can replace a popular empirical model of the energetics.},
doi = {10.1021/acs.jpcc.7b00099},
journal = {Journal of Physical Chemistry. C},
number = 11,
volume = 121,
place = {United States},
year = {2017},
month = {3}
}