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　理学研究科化学専攻　安倍　学教授，藤田　祥基さん，九州大学鈴木達也さん，　吉澤　一成教授，塩田淑仁准教授の論文が、BCSJ誌Vol. 89 No. 7の優秀論文として、Selected Paperに選出されました

　理学研究科化学専攻　安倍　学教授，藤田　祥基さん，九州大学鈴木達也さん，　吉澤　一成教授，塩田淑仁准教授の論文が、BCSJ誌Vol. 89 No. 7の優秀論文として、Selected Paperに選出されました。

【論文タイトル】

「Computational Study of Cyclobutane-1,3-diylidene Dicarbenes: Ground-State Spin Multiplicity and New Strategy Toward the Synthesis of Bicyclo[1.1.0]but-1(3)-enes」

【論文概要】

　For over 50 years, pyramidalized alkenes, in which one or both of the doubly bonded carbons do not lie in the same plane as the three atoms attached to them, have attracted much attention because of their unique bonding and molecular structures. The characteristics of pyramidalized alkenes are higher electrophilicity and lower p–p* excitation energy than those with planar alkenes, which are mainly originated from the low-lying LUMO energy in distorted π-bonding systems.The distorted p-bonding structure is regarded as the smallest part of the curved p molecules such as fullerenes, corannulenes, sumanenes, and hoop-shaped p-conjugated compounds. Since the 1990s, curved π-conjugated molecules have attracted significant interest in many fields of science. The smallest pyramidalized alkene, i.e., bicyclo[1.1.0]but-1(3)-ene (BBE), which has been determined to be an equilibrium structure, has not yet been isolated.

　In the present study, a new strategy using the dimerization of highly reactive divalent species such as carbene (R₂C:) was designed to synthesize highly distorted double-bonding BBE structures. Coupled-cluster calculations were performed for cyclobutane-1,3-diylidene dicarbenes at the CCSD(T)//CCSD/cc-pVDZ level of theory, in which the ground-state spin multiplicity and the structures of unique molecules were investigated in detail. The closed-shell singlet state (S_σπ) with a bicyclo[1.1.0]but-1(3)-ene (BBE) structure found to be the ground-state was much lower in energy than the corresponding singlet dicarbene structure (S_**), the quintet state (Q), and the triplet state (T), suggesting that the hitherto experimentally unknown BBE structure can be synthesized by the intramolecular dimerization of two carbene units. Two unique structures, (T_σ) with a C1–σ–C3 bond and (T_π) with a C1–π–C3 bond, were found to be the equilibrium structures for the triplet state of cyclobutane-1,3-diylidene dicarbenes.

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