On the electronic character of localized singlet 2,2-dimethoxycyclopentane-1,3-diyl diradicals: substituent effects on the lifetime

Manabu Abe; Waldemar Adam; Michihiro Hara; Masanori Hattori; Tetsuro Majima; Masatomo Nojima; Kei Tachibana; Sachiko Tojo

doi:10.1021/ja026301l

On the electronic character of localized singlet 2,2-dimethoxycyclopentane-1,3-diyl diradicals: substituent effects on the lifetime

J Am Chem Soc. 2002 Jun 12;124(23):6540-1. doi: 10.1021/ja026301l.

Authors

Manabu Abe¹, Waldemar Adam, Michihiro Hara, Masanori Hattori, Tetsuro Majima, Masatomo Nojima, Kei Tachibana, Sachiko Tojo

Affiliation

¹ Department of Materials Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871, Osaka, Japan. abe@ap.chem.eng.osaka-u.ac.jp

PMID: 12047167
DOI: 10.1021/ja026301l

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.