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

摘要

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 H2(O) and D2O. The technique uses tris (2,2'-bipyridine) ruthenium(II) dication (Ru(bipy)(3)(2+)) 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 fate constant of 2.1 (+/- 0.3) x 10(6) mol(-1) dm(3) s(-1) has been determined for the reaction of 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) x 10(5) mol(-1) dm(3) s(-1). Chemical reaction, rather than physical quenching, is the dominant reaction route for gelatins and O-2. [References: 15]