title: Reversible Photoisomerization among Triplet Amino Naphthylnitrene, Triplet Diimine Biradical, and Indazole: Matrix-Isolation IR Spectra of 8-Amino-1-naphthylnitrene, 1,8-Naphthalenediimine, and 1,2-Dihydrobenz[cd]indazole.
abstract: Reaction mechanisms of nitrene, one of the most famous biradicals, have been frequently studied, and many spectral data have been obtained so far. In the present study, the experimental IR spectra of triplet 8-amino-1-naphthylnitrene (3ANN), a triplet diimine biradical 1,8-dihydro-1,8-naphthalenediimine (3DND), and 1,2-dihydrobenz[cd]indazole (DBI), which are produced in the UV photolysis of 1,8-diaminonaphthalene in an Ar matrix and identified by a combination method of IR spectroscopy and DFT quantum chemical calculations, are first reported.3ANN is found to change to DBI by hydrogen-atom migration with bond making between the two nitrogen atoms upon visible-light irradiation (λ > 580 nm) with its backward reaction caused by 350 nm irradiation. In addition,3ANN isomerizes to3DND by 700 nm irradiation, while its backward reaction occurs upon 500 nm irradiation. The wavelength dependences of these photoisomerizations are explained in terms of their electronic transition energies estimated by time-dependent DFT calculations. It is concluded that the novel reversible photoisomerization system among3ANN,3DND, and DBI is totally different from the well-known photoisomerization between phenylnitrene and a seven-membered cyclic compound.
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering (BASE), Tokyo University of Agriculture and Technology , 2-24-16 Naka-cho, Koganei city, Tokyo 184-8588, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Okamura
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering (BASE), Tokyo University of Agriculture and Technology , 2-24-16 Naka-cho, Koganei city, Tokyo 184-8588, Japan.
authors.forename: Nobuyuki
authors.identifier: http://orcid.org/0000-0002-5722-4596
authors.initials: N
authors.lastname: Akai
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering (BASE), Tokyo University of Agriculture and Technology , 2-24-16 Naka-cho, Koganei city, Tokyo 184-8588, Japan.
authors.forename: Munetaka
authors.initials: M
authors.lastname: Nakata