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Electronic and optical properties of pyrrole and thiophene oligomers: A density functional theory study
Author(s) -
Chen Juan,
Zhu Xingfeng,
Luo Chenglin,
Dai Yafei
Publication year - 2017
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25453
Subject(s) - polarizability , oligomer , thiophene , density functional theory , chemistry , charge density , pyrrole , hyperpolarizability , dipole , computational chemistry , crystallography , molecule , polymer chemistry , organic chemistry , physics , quantum mechanics
The conductive mechanism of pyrrole (Py) and thiophene (Th) oligomers is investigated in the framework of density functional theory. Geometric constructions and electronic structures of neutral n ‐Py/ n ‐Th and oxidized n ‐Py m + / n ‐Th m + oligomers (6 ≤ n ≤ 48, 2 ≤ m ≤ 18) are reported as a function of oligomer length. The charges in the oxidized oligomers have a localized distribution along the oxidized n ‐Py m + / n ‐Th m + oligomers, and each set of two positive charges is localized in one area. Therefore, the charge carriers in oxidized n ‐Py m + / n ‐Th m + oligomers are bipolarons. Furthermore, the nonlinear optical properties of the n ‐Py/ n ‐Th oligomers are investigated, for which the static polarizability α, the first polarizability β, and the second polarizability γ are calculated. When the ratio of m / n is 1/3, the static polarizability <α> and the polarizability anisotropy Δα are maximized. In addition, neutral n ‐Py/ n ‐Th oligomers have maximum <γ> values. The values of β were determined mainly by the dipole of the molecule, while the values of γ were closely related to the aromaticity of the oligomer. The stronger the aromaticity, the bigger the γ value. All calculations indicate that the polarizability and absorption spectrum can be tuned by controlling the oxidation level, making these oligomers applicable as good nonlinear optical materials.