title: Tuning Nonlinear Optical Properties by Altering the Diradical and Charge-Transfer Characteristics of Chichibabin's Hydrocarbon Derivatives.
abstract: Heteroatomic derivatives of Chichibabin's hydrocarbon are explored theoretically to highlight the relationship between the electronic structure and nonlinear optical (NLO) properties. The results show that the systems are divided into two classes: one that has intermediate electronic structure between two main contributing resonance structures, and a second with an electronic structure that is approximated by only one resonance structure. It is found that the former class of derivatives exhibits approximately one-order larger static second hyperpolarizability (γ) than the latter class, because of either their intermediate diradical or charge-transfer (CT) characteristics. The asymmetric systems are further scrutinized by using the static electric field model, which shows that the intermediate CT character is essential for the very large enhancement of γ in the asymmetric systems. These results not only clarify the structure-property relationships of open-shell singlet NLO compounds with redox switching properties, but also shed light on a new and unexplored class of closed-shell NLO systems generated by the introduction of intermediate CT nature into open-shell singlet systems.
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Fukuda
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 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, Toyonaka, Osaka, 560-8531, Japan.|Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Kitagawa
authors.affiliation: Laboratoire de Chimie Théorique, University of Namur, rue de Bruxelles, 61, 5000, Namur, Belgium.
authors.forename: Benoît
authors.initials: B
authors.lastname: Champagne
authors.affiliation: IFMRI, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka, 563-8577, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kamada
authors.affiliation: Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
authors.forename: Yohsuke
authors.initials: Y
authors.lastname: Yamamoto
authors.affiliation: Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.|Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakano
keywords: charge transfer; nonlinear optics; open-shell singlet; radicals; redox chemistry