Narrow-energy gap conjugated polymers based on benzobisthiadiazole and thiadiazoloquinoxaline: DFT and TDDFT study
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ORIGINAL PAPER
Narrow-energy gap conjugated polymers based on benzobisthiadiazole and thiadiazoloquinoxaline: DFT and TDDFT study Pervin Ünal Civcir 1
&
Ezgi Özen 1
&
Can Karadeniz 2
Received: 16 July 2020 / Accepted: 13 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Herein, the HOMO–LUMO energy gaps (Eg) and UV spectra of benzo[1,2-c:4,5-c’]bis([1,2,5]thiadiazole (BBT) and [1,2,5]thiadiazolo[3,4-g]quinoxaline (TQ)-based donor–acceptor–donor type-conjugated polymers were computed by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-31G(d,p) level. The donor groups consist of thiophene (TH), 3,4-ethylenedioxythiophene (EDOT), and 3,4-propylene dioxythiophene (ProDOT) units and the bisthiadiazole and thiadiazoloquinoxaline were chosen as electron acceptor groups. To examine the effects of the alkyl side chain on the molecular structure and Eg of the polymer, methyl groups were added at the 3,4-, 2,3-, and 3,3-positions of TH, EDOT, and ProDOT donor groups, respectively. Our calculated HOMO-LUMO energy gaps are in the range of 0.05 to 1.37 eV. The calculation results show that the energy gaps are in line with the available experimental values. The novel BBT and TQ derivatives with improved optical and electronic properties may find use in electronic applications.
Keywords TDTFT . Benzobisthiadiazole . Thiadiazoloquinoxaline . Thiophene . EDOT . ProDOT
Introduction Highlights • A series of donor–acceptor–donor type polymers based on benzobisthiadiazole and thiadiazoloquinoxaline are modeled • Modeled polymers have remarkably low HOMO-LUMO energy gap values, which are range from 0.05 to 1.37 eV. • The novel ProDOT and all methyl derivatives of the studied oligomers with improved optical and electronic properties may be used in the electronic applications. • DFT calculations give good results for the HOMO-LUMO gaps of this type of polymers Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00894-020-04541-y) contains supplementary material, which is available to authorized users. * Pervin Ünal Civcir [email protected] Ezgi Özen [email protected] 1
Department of Chemistry, Faculty of Science, Ankara University, 06100 Ankara, Turkey
2
İstanbul, Turkey
The most commonly used method to synthesize and design new organic conductive polymers with a low band gap is the usage of the molecules with donor–acceptor–donor (D-A-D) repeat units. Thiophene (TH), 3,4-ethylenedioxythiophene (EDOT), and 3,4-propylenedioxythiophene (ProDOT) as donor groups and benzothiadiazole (BTD), benzobisthiadiazole (BBT), and thiadiazolo[3,4-g]quinoxaline (TQ) as acceptor groups are the most common examples of the D-A-D type of polymer. Recent reports show that some low band gap polymers with BBT and TQ moieties are synthesized and some of them present very good results in electronic applications. Their applications are light-emitting devices (LED), organic field-effect transisto
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