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Coulombic effects in the quenching of photoexcited tris(2,2'-bipyridine)ruthenium(II) and related complexes by methyl viologen

Journal Article · · J. Phys. Chem.; (United States)
DOI:https://doi.org/10.1021/j100487a006· OSTI ID:5689515
Both intensity and lifetime measurements have been used to study the quenching of luminescence of several ruthenium(II)-bipyridyl complexes by methyl viologen (1,1'-dimethyl-4,4'-bipyridinium chloride) in aqueous salt solutions. For the neutral complex (Ru(bpy)/sub 2/(CN)/sub 2/)/sup 0/, no salt effect is observed and the quenching rate constant is near the diffusion-controlled limit. Another neutral complex, (Ru(bpy)/sub 2/(bpy(COO/sup -/)/sub 2/))/sup 0/, exhibits a small negative salt effect, perhaps due to its highly dipolar structure. The three positively charged complexes studied, (Ru(bpy)/sub 3/)/sup 2 +/, (Ru(bpy)/sub 2/(bpy(CH/sub 3/)/sub 2/))/sup 2 +/, and (Ru(bpy)/sub 2/(bpy(COOH)/sub 2/))/sup 2 +/, are all quenched with similar rate constants and show similar large positive salt effects; k/sub q/ increases approximately sixfold when (NaCl) is increased from 0.03 to 1.5 M, and at the highest salt content is within a factor of 2 of the diffusion-controlled limit. While the results are qualitatively consistent with the conventional Bronsted-Debye treatment of ionic reaction rates, large specific ion effects are indicated by limited data with NaClO/sub 4/ as a neutral salt.
Research Organization:
General Electric Co., Schenectady, NY
OSTI ID:
5689515
Journal Information:
J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 83:24; ISSN JPCHA
Country of Publication:
United States
Language:
English