大阪大学 · 材料科学
Ryohei Kishi教授の研究室では、電子状態が複雑に絡む開殻系スピン状態を有する分子、特に三重項状態やディラジカルを示す系の電子構造と光学的非線形性を、高精度な電子状態計算手法を用いて解明しています。特に、密度汎関数理論（DFT）と配置積み込み（CI）法を組み合わせた新規計算手法の開発と、それらを用いた第二ハイパーポラリザビリティの定量的評価が中心です。また、新しいπ共鳴系やキラルな芳香族骨格を有する有機分子の合成とその電子的性質の解明にも取り組んでいます。
Figures are computed from collected data and may differ slightly.
Within the spin-unrestricted density functional theory (DFT) the long-range correction (LC) scheme combined with the Becke-Lee-Yang-Parr exchange-correlation functional, referred to as LC-UBLYP method, has been applied to the calculation of the second hyperpolarizability (gamma) of open-shell singlet diradical systems of increasing complexity and has demonstrated good performance: (i) for the simplest H(2) dissociation model, the gamma values calculated by the LC-UBLYP method significantly overs
Bis-periazulene (cyclohepta[<i>def</i>]fluorene), which is an unknown pyrene isomer, was synthesized as kinetically protected forms. Its triaryl derivatives <b>1c</b>-<b>e</b> exhibited the superimposed electronic structures of peripheral, polarized, and open-shell π-conjugated systems. In contrast to previous theoretical predictions, bis-periazulene derivatives were in the singlet ground state. Changing an aryl group controlled the energy gap between the lowest singlet-triplet states.
Ab initio spin-flip configuration interaction (SF-CI) methods with the finite-field (FF) scheme are applied to the calculation of static second hyperpolarizabilities (γ) of several singlet diradical systems, i.e., the model H2 molecule under dissociation, p-quinodimethane, o-quinoid five-membered ring, and 1,4-bis(imidazole-2-ylidene)cyclohexa-2,5-diene (BI2Y) models. The SF-CI method using the UHF reference wave function provides the qualitatively correct diradical character (y) dependence of γ
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