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USE OF TRIS (2,2‘‐BIPYRIDINE) RUTHENIUM(II) DICATION IN A NOVEL METHOD FOR THE DETERMINATION OF SINGLET OXYGEN REACTION RATES: APPLICATION TO STUDIES OF GELATIN
Author(s) -
Douglas Peter,
Evans Philippa C.,
Henbest Kevin
Publication year - 1995
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1995.tb08614.x
Subject(s) - chemistry , singlet oxygen , ruthenium , dication , reaction rate constant , quenching (fluorescence) , tris , photochemistry , methanol , bipyridine , luminescence , oxygen , reaction rate , singlet state , kinetics , excited state , fluorescence , molecule , catalysis , organic chemistry , materials science , biochemistry , physics , optoelectronics , quantum mechanics , nuclear physics , crystal structure
— A novel method for the determination of singlet oxygen reaction rate constants is described and applied to studies of cyclohexadiene in methanol and gelatins in H 2 O and D 2 O. The technique uses tris (2,2′‐bipyridine) ruthenium(II) dication (Ru(bipy) 32+ ) as both singlet oxygen sensitizer and in situ oxygen concentration monitor during irradiation of sealed samples. Because of the high efficiency with which the luminescence of Ru(bipy) 3 2+* can be detected, and the fact that emission lifetimes are used, the method offers some advantages over those previously described. The advantages and disadvantages of the method are discussed. A rate constant of 2.1 (±0.3) x 10 6 mol ‐1 dm 3 s ‐1 has been determined for the reaction of 1 O 2 with cyclohexadiene in methanol. For two different photographic gelatins the sums of reaction and quenching rate constants are 2.0 (±0.4) x 10 6 and 3.1 (±2.0) x 10 5 mol ‐1 dm 3 s ‐1 ; for swine skin gelatin this value is 3.9 (±2.4) × 10 5 mol ‐1 dm 3 s ‐1 . Chemical reaction, rather than physical quenching, is the dominant reaction route for gelatins and 1 O 2 .