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Title: Comparative Computational Study of Electronic Excitations of Neutral and Charged Small Oligothiophenes and Their Extrapolations Based on Simple Models

Abstract

This work reports electronic excitation energies of neutral and charged oligothiophenes (OT n) with repeat unit n = 2–6 computed by routinely used semiempirical and time-dependent density functional theory (TD-DFT) methods. More specifically, for OT n, OT n +, and OT n , we calculated vertical transition energies for electronic absorption spectroscopy employing the Zerner’s version of intermediate neglect differential overlap method for structures optimized by the PM6 semiempirical method and the TD-DFT method with three different functionals, B3LYP, BVP86, and M06-2X, for structures optimized by the ground-state DFT method employing the same functionals. We also calculated vertical transition energies for the emission spectroscopy from the lowest singlet excited states by employing the TD-DFT method for the structures optimized for the lowest singlet excited states. In addition to computational results in vacuum, solution phase data calculated at the level of polarizable continuum model are reported and compared with available experimental data. Most of the data are fitted reasonably well by two simple model functions, one based on a Frenkel exciton theory and the other based on the model of independent electrons in a box with sinusoidal modulation of potential. Despite similar levels of fitting performance, the two models produce distinctivelymore » different asymptotic values of excitation energies. Comparison of these with available experimental and computational data suggests that the values based on the exciton model, while seemingly overestimating, are closer to true values than those based on the other model. This assessment is confirmed by additional calculations for a larger oligomer. The fitting parameters offer new means to understand the relationship between electronic excitations of OTs and their sizes and suggest the feasibility of constructing simple coarse-grained exciton-bath models applicable for aggregates of OTs.« less

Authors:
 [1];  [2]; ORCiD logo [2]
  1. Queens College, City Univ. of New York, NY (United States). Dept. of Chemistry and Biochemistry
  2. Queens College, City Univ. of New York, NY (United States). Dept. of Chemistry and Biochemistry; City Univ. of New York, NY (United States). Graduate Center. Ph.D. Programs in Chemistry and Physics. Initiative for the Theoretical Sciences
Publication Date:
Research Org.:
Queens College, City Univ. of New York, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
OSTI Identifier:
1503369
Alternate Identifier(s):
OSTI ID: 1508799
Grant/Contract Number:  
SC0001393; CHE-1362926
Resource Type:
Published Article
Journal Name:
ACS Omega
Additional Journal Information:
Journal Volume: 4; Journal Issue: 3; Journal ID: ISSN 2470-1343
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; fluorescence; molecular structure; polythiophenes; potential energy; quantum mechanical methods; quantum transition; solvation; spectra; theory

Citation Formats

Kowalczyk, Marta, Chen, Ning, and Jang, Seogjoo J. Comparative Computational Study of Electronic Excitations of Neutral and Charged Small Oligothiophenes and Their Extrapolations Based on Simple Models. United States: N. p., 2019. Web. doi:10.1021/acsomega.8b02972.
Kowalczyk, Marta, Chen, Ning, & Jang, Seogjoo J. Comparative Computational Study of Electronic Excitations of Neutral and Charged Small Oligothiophenes and Their Extrapolations Based on Simple Models. United States. doi:10.1021/acsomega.8b02972.
Kowalczyk, Marta, Chen, Ning, and Jang, Seogjoo J. Mon . "Comparative Computational Study of Electronic Excitations of Neutral and Charged Small Oligothiophenes and Their Extrapolations Based on Simple Models". United States. doi:10.1021/acsomega.8b02972.
@article{osti_1503369,
title = {Comparative Computational Study of Electronic Excitations of Neutral and Charged Small Oligothiophenes and Their Extrapolations Based on Simple Models},
author = {Kowalczyk, Marta and Chen, Ning and Jang, Seogjoo J.},
abstractNote = {This work reports electronic excitation energies of neutral and charged oligothiophenes (OTn) with repeat unit n = 2–6 computed by routinely used semiempirical and time-dependent density functional theory (TD-DFT) methods. More specifically, for OTn, OTn+, and OTn–, we calculated vertical transition energies for electronic absorption spectroscopy employing the Zerner’s version of intermediate neglect differential overlap method for structures optimized by the PM6 semiempirical method and the TD-DFT method with three different functionals, B3LYP, BVP86, and M06-2X, for structures optimized by the ground-state DFT method employing the same functionals. We also calculated vertical transition energies for the emission spectroscopy from the lowest singlet excited states by employing the TD-DFT method for the structures optimized for the lowest singlet excited states. In addition to computational results in vacuum, solution phase data calculated at the level of polarizable continuum model are reported and compared with available experimental data. Most of the data are fitted reasonably well by two simple model functions, one based on a Frenkel exciton theory and the other based on the model of independent electrons in a box with sinusoidal modulation of potential. Despite similar levels of fitting performance, the two models produce distinctively different asymptotic values of excitation energies. Comparison of these with available experimental and computational data suggests that the values based on the exciton model, while seemingly overestimating, are closer to true values than those based on the other model. This assessment is confirmed by additional calculations for a larger oligomer. The fitting parameters offer new means to understand the relationship between electronic excitations of OTs and their sizes and suggest the feasibility of constructing simple coarse-grained exciton-bath models applicable for aggregates of OTs.},
doi = {10.1021/acsomega.8b02972},
journal = {ACS Omega},
number = 3,
volume = 4,
place = {United States},
year = {2019},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1021/acsomega.8b02972

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