KINETIC SALT EFFECTS IN THE QUENCHING OF THE EXCITED-STATE OF THE TRIS (2,2'-BIPYRIDINE) RUTHENIUM(II) COMPLEX BY ANTHRAQUINONES

The quenching reaction of the excited state of the tris (2,2'-bipyridi ne) Ruthenium (II) complex (Rubpy) by various anthraquinones (2-methy l-, 1-chloro-, and l-nitro-anthraquinone; MAQ, ClAQ, and NAQ) has been investigated as a function of ionic strength in acetonitrile using th e salts Et(4)NClO(4), NaClO4 and LiClO4. The Gibbs energy Delta G degr ees of the reaction, kinetic rate constants of all reaction steps, the quantum yield, and transient absorption spectra of the anthraquinone radical anions were determined. The rate constant of the back electron transfer in the geminate radical ion pair shows Marcus-inverted behav iour.