title: On the electronic character of localized singlet 2,2-dimethoxycyclopentane-1,3-diyl diradicals: substituent effects on the lifetime.
abstract: Photodenitrogenation of the diazenes 4 affords exclusively the housanes 5 through intramolecular cyclization of the spectrally detected and characterized singlet diradicals 3. The lifetime of singlet diradical 3, determined by transient absorption measurements, depends on the Y and Z substituents at the para position of the phenyl ring and has the following order: Y, Z = OMe, OMe > OMe, CN > CN, CN > OMe, H > Cl, Cl approximately CN, H approximately Me, Me > H, H. This unprecedented substituent effect reveals stabilization of the singlet 2,2-dimethoxycyclopentane-1,3-diyl diradicals 3 through radical, zwitterionic, pi-bonding, and hyperconjugative structures.
authors.affiliation: Department of Materials Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871, Osaka, Japan. abe@ap.chem.eng.osaka-u.ac.jp
authors.forename: Manabu
authors.initials: M
authors.lastname: Abe
authors.forename: Waldemar
authors.initials: W
authors.lastname: Adam
authors.forename: Michihiro
authors.initials: M
authors.lastname: Hara
authors.forename: Masanori
authors.initials: M
authors.lastname: Hattori
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Majima
authors.forename: Masatomo
authors.initials: M
authors.lastname: Nojima
authors.forename: Kei
authors.initials: K
authors.lastname: Tachibana
authors.forename: Sachiko
authors.initials: S
authors.lastname: Tojo