Poly(pyridine)ruthenium(II)-photoinduced redox reactions of bipyridinium cations, poly(pyridine)rhodium complexes, and osmium ammines

Journal Article · Wed Jun 30 00:00:00 EDT 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00377a013· OSTI ID:6733515

Creutz, C; Keller, A D; Sutin, N; Zipp, A P

The quenching of *RuL/sub 3//sup 2 +/ (L is a 2,2'-bipyridine or 1,10-phenanthroline derivative) emissions by three classes of oxidants Q has been examined. The results are discussed in terms of the Marcus electron-transfer model recast in a preequilibrium formalism. Substituted bipyridinium cations (methyl viologen and related compounds) undergo thermodynamically favorable reduction with a driving force ranging from 0.1 to 0.7 eV and rate constants in the range (0.4-2.0) x 10/sup 9/ M/sup -1/s/sup -1/, consistent with a diffusion rate constant of 2.0 x 10/sup 9/ M/sup -1/s/sup -1/ and an exchange rate constant of approx.10/sup 6/ M/sup -1/s/sup -1/ for the Q-Q couples. The yields of the separated redox products RuL/sub 3//sup 3 +/ and Q/sup -/ (typically 0.1 mol einstein/sup -1/ per quenching act) require K/sub 30/, the ''intramolecular'' back-reaction rate constant (to re-form ground-state RuL/sub 3//sup 2 +/ and Q), to be (2-4) x 10/sup 10/ s/sup -1/. Since K/sub 30/ increases weakly with driving force in this series, there is no evidence for inverted behavior despite the fact the ..delta..G/sup 0//sub 30/ is approx.-2 eV. With Q = Rh(4,4'-(CH/sub 3/)/sub 2/bpy)/sub 3//sup 3 +/, the quenching rate constants, k/sub q/ = (0.001-1.0) x 10/sup 9/ M/sup -1/s/sup -1/, exhibit a great sensitivity to the reducing power of *RuL/sub 3//sup 2 +/ and have been fitted to k/sub 11/ approx. = 2 x 10/sup 9/ M/sup -1/s/sup -1/ and E/sup 0//sub Q,Q/sup -// = -0.97 V for the RhL/sub 3//sup 3 +/-RhL/sub 3//sup 2 +/ couple. This E/sup 0/ value is strikingly similar to that (-0.9 V vs. aqueous SCE) obtained via cyclic voltammetry in acetonitrile. The cyclic voltammetry of the RhL/sub 3//sup 3 +/ complexes in water has been reexamined, and it is concluded that the irreversibility observed is due to ligand loss from rhodium(I).

• Research Organization: Brookhaven National Lab., Upton, NY
• OSTI ID: 6733515
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 104:13
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
08 HYDROGEN
BIPYRIDINES
ELECTRON TRANSFER
OSMIUM COMPLEXES
PHENANTHROLINES
RHODIUM COMPLEXES
RUTHENIUM COMPLEXES
AMMINES
CATIONS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
EXPERIMENTAL DATA
QUENCHING
VOLTAMETRY
AZINES
CHARGED PARTICLES
COMPLEXES
DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
IONS
KINETICS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIDINES
REACTION KINETICS
TRANSITION ELEMENT COMPLEXES
YIELDS
400500* - Photochemistry
080100 - Hydrogen- Production
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)