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Properties of Excited Ketyl Radicals of Benzophenone Analogues Affected by the Size and Electronic Character of the Aromatic Ring Systems
Author(s) -
Sakamoto Masanori,
Cai Xichen,
Fujitsuka Mamoru,
Majima Tetsuro
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500409
Subject(s) - ketyl , benzophenone , photochemistry , flash photolysis , excited state , radical , chemistry , nanosecond , laser , organic chemistry , reaction rate constant , optics , atomic physics , kinetics , physics , quantum mechanics
The properties of benzophenone ketyl radical analogues with large aromatic ring systems, such as naphthylphenylketone ( 2 ), 4‐benzoylbiphenyl ( 3 ), and bis(biphenyl‐4‐yl)methanone ( 4 ), were investigated in the excited state by using nanosecond–picosecond two‐color two‐laser flash photolysis. Fluorescence and transient absorption spectra of ketyl radicals of 2 – 4 in the excited state were observed for the first time. The fluorescence and properties of the excited ketyl radicals were significantly affected by the size and electronic properties of the aromatic ring systems. The reactivity of the ketyl radicals in the excited state with several quenchers was examined and they were found to show reactivity toward N , N ‐diethylaniline. In addition, for the benzophenone ketyl radical, a unique quenching process of the radical in the excited state by the ground‐state parent molecule was found. The factors regulating the fluorescence lifetime of the ketyl radicals in the excited state are discussed quantitatively.