title: Diradical Character Tuning for the Third-Order Nonlinear Optical Properties of Quinoidal Oligothiophenes by Introducing Thiophene-S,S-dioxide Rings.
abstract: To create a design guideline for efficient third-order nonlinear optical (NLO) molecules, the chain-length (n) dependences of the diradical character y and the longitudinal second hyperpolarizability γ of quinoidal oligothiophenes (QTs), from monomers to octamers, involving thiophene-S,S-dioxide rings are investigated by using the density functional theory method. It turns out that the diradical character of the modified QTs is reduced as compared to those of the pristine QTs. By introducing an appropriate number of oxidized rings into the QT framework, intermediate y values can be achieved even in the systems with large values of n, in which the pristine QTs are predicted to have pure diradical character. Such intermediate diradical oligomers are shown to exhibit enhanced γ values as compared to the pristine QTs with the same value for n. From the calculation results, the introduction of the optimal number of thiophene-S,S-dioxide rings is predicted to be an efficient chemical modification for optimizing the third-order NLO properties of open-shell QTs through tuning the diradical characters.
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan. rkishi@cheng.es.osaka-u.ac.jp.
authors.forename: Ryohei
authors.initials: R
authors.lastname: Kishi
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Shoki
authors.initials: S
authors.lastname: Ochi
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Shioh
authors.initials: S
authors.lastname: Izumi
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Makino
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Nagami
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Jun-ya
authors.initials: JY
authors.lastname: Fujiyoshi
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Matsushita
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Michika
authors.initials: M
authors.lastname: Saito
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka, 560-8531, Japan. mnaka@cheng.es.osaka-u.ac.jp.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakano
keywords: density functional calculations; diradicals; oligthiophenes; open-shell singlet states; optical properties