81655-93-8Relevant academic research and scientific papers
Poly(pyridine)rutenium(II)-Photoinduced Redox Reactions of Bipyridinium Cations, Poly(pyridine)rhodium Complexes, and Osmium Ammines
Creutz, Carol,Keller, Andrew D.,Sutin, Norman,Zipp, Arden P.
, p. 3618 - 3627 (1982)
The quenching of *RuL32+ (L is a 2,2'-bipyridine or 1,10-phenanthroline derivative) emission by there classes of oxidants Q has been examined The results were discussed in terms of Marcus electron-transfer model recast in the preequilibrium formalism.Substituted bipyridinium cations (methyl viologen and related compounds undergo thermodinamically favorable reduction with driving force ranging from 0.1 to 0.7 eV and rate constants in range (0.4-2.0)*109 M-1s-1, consistent with a diffusion rate constant of 2.0*109 M-1s-1 and an exchange rate constant c.a. 106 M-1s-1 for Q-Q- couples.The yields of the separated redox products RuL3+ and Q- (typically 0.1 mol einstein -1 per quenching act) require k30, the intramolecular back-reduction rate constant (to re-form ground-state RuL32+ and Q), to be (2-4)*1010s-1.Since k30 increases weakly with driving force in this series, there is no evidence for inverted behavior despite the fact that ΔG030 is c.a. -2eV.With Q=Rh(4,4'-(CH3)2bpy)33+, the quenching rate constants, kq=(0.001-1.0)*109 M-1s-1, exhibit a great sensitivity to the reducing power of *RuL32+ and have been fitted o k11 c.a. 2*109 M-1s-1 and E0Q.Q'=-0.97 V for the RhL33+-RhL32+ couple.This E0 value is strikingly similar to that (-0.9 V vs. aqueous SCE) obtained via cyclic voltammetry in acetonitrile.The cyclic voltammetry of the RhL33+ complexes in water has been reexamined, and it is concluded that the irreversibility observed is due to ligand loss from rhodium(I).After correction for an energy transfer component (kq=kel+kem), the rate constants for reduction of OsIII(NH3)5X (kel c.a. 2*106-2*108 M-1s-1 for X=Cl,Br,I,H2O,or NH3) and for oxidation of Os(NH3)5N22+ are in accord with theoretical expectations and osmiun (III)-osmium(II) exchange rates in the range 102-105 M-1s-1.Some observations, conserning Os(NH3)5Cl+. which was generated and characterized by radiation chemistry and flash photolysis tichniques, are also reported.
