title: Theoretical Study on the Second Hyperpolarizailities of Oligomeric Systems Composed of Carbon and Silicon π-Structures.
abstract: To explore the prospect of molecules involving silicon-silicon multiple bonds as nonlinear optical molecular systems, the relationship between the structure and the second hyperpolarizabilities γ of the oligomeric systems composed of carbon and silicon π-structures is investigated using the density functional theory method. It is found that these compounds indicate intramolecular charge transfer (ICT) from the silicon units to the carbon units together with nonzero diradical characters. The γ values of these compounds are shown to be 2-13 times as large as those of the carbon analogs. Although asymmetric carbon and silicon π-systems exhibit comparable enhancement to the corresponding symmetric systems, donor-π-donor structures exhibit remarkable enhancement of γ despite of their both-end short silicon π-chain moieties (donor units). Further analysis using the odd electron and γ densities clarifies that the intermediate diradical character also contributes to the enhancement of γ. These results predict that even short π-conjugated silicone moieties can cause remarkable enhancement of γ by introducing them into π-conjugated hydrocarbon structures.
authors.affiliation: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. hiroshi.matsui@cheng.es.osaka-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. takanori.nagami@cheng.es.osaka-u.ac.jp.
authors.forename: Takanori
authors.initials: T
authors.lastname: Nagami
authors.affiliation: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. shota.takamuku@cheng.es.osaka-u.ac.jp.
authors.forename: Shota
authors.initials: S
authors.lastname: Takamuku
authors.affiliation: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. soichi@cheng.es.osaka-u.ac.jp.
authors.forename: Soichi
authors.initials: S
authors.lastname: Ito
authors.affiliation: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. kitagawa@cheng.es.osaka-u.ac.jp.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Kitagawa
authors.affiliation: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. mnaka@cheng.es.osaka-u.ac.jp.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nakano
mesh_terms: D000465:Algorithms; D002244:Carbon / Q000737:chemistry*; D008958:Models, Molecular; D008962:Models, Theoretical; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D011108:Polymers; D002244:Carbon; D012825:Silicon
keywords: density functional theory; diradical; second hyperpolarizability; silicon-silicon double bond