局在化一重項ジラジカルの長寿命化：結合ホモリシス過程の新展開と新奇結合様式（C-π-C）の創製

抄録

Localized singlet diradicals are key intermediates in bond-homolyses. Thorough studies of the reactive species are essential to clarify the mechanisms of the homolytic bond-cleavage and -formation processes. In general, the singlet diradicals are quite short-lived due to the fast radical-radical coupling reactions. The short-lived characteristic has retarded the thorough study on bond-homolyses. In the last two decades, the author and his research group have enjoyed conducting fundamental studies of generating spectroscopically detectable singlet diradicals to clarify the chemistry of localized singlet diradicals. Recently, a new series of long-lived singlet diradicals, viz. 1,2-diazacyclopentane-3,5-diyl and singlet diradical having macrocyclic structures, have been identified, and their electronic structures and novel reactivities were thoroughly studied using laser-flash photolysis (LFP), product analysis, emission analyses, and computational studies. During the research study, two new concepts in chemistry have emerged; (1) π-single bonding (C-π-C) and (2) the third isomer in bond-homolysis processes, i.e. puckered singlet diradicals. This article describes first a short history of localized diradicals, then, the nitrogen-atom effect on the reactivity of singlet diradicals, the chemistry of π-single bonded species, the stereoselectivity in the photochemical denitrogenation reactions, and the adiabatic bond-homolysis process in the electronically excited states.