Photodynamics of the tris(2,2'-bipyrazine)ruthenium(2+)/methylviologen/EDTA system in aqueous solution
Luminescence quenching and flash photolysis (pulsed laser and conventional) techniques have been employed to study the photodynamics of the Ru(bpz)/sub 3//sup 2 +//EDTA system in aqueous solution (bpz = 2,2'-bipyrazine; MV/sup 2 +/ = methylviologen). The quenching of *Ru(bpz)/sub 3//sup 2 +/ by EDTA in alkaline solution via Stern-Volmer kinetics (kappa/sub q/ = 6.9 x 10/sup 8/ and 7.7 x 10/sup 8/ M/sup -1/s/sup 1/ at pH 8.7 and 11.0, respectively) generates Ru(bpz)/sub 3//sup +/ which reacts with MV/sup 2 +/ (kappa = 4.5 x 10/sup 9/ M/sup -1/ s/sup -1/) to yield MV/sup +/; the reducing EDTA radical, formed from the irreversible transformation of the species obtained from the oxidation of EDTA, reacts with MV/sup 2 +/ (kappa = 1.5 x 10/sup 9/ M/sup -1/ s/sup -1/) to yield a second equivalent of MV/sup +/. At pH 4.7, the quenching of *Ru(bpz)/sub 3//sup 2 +/ by EDTA does not follow Stern-Volmer kinetics; kappa/sub q/ approaches approx.2 x 10/sup 8/ and approx.2 x 10/sup 7/ M/sup -1/ s/sup -1/ in the limits of low and high (EDTA), respectively. The quantum yields of MV/sup +/ in acidic solution are dramatically lower than in neutral and alkaline solution due to the lower efficiencies of the quenching and cage release processes and the decreased reactivities of the protonated forms of Ru(bpz)/sub 3//sup +/ and reducing EDTA radicals toward MV/sup 2 +/.
- Research Organization:
- Boston Univ., MA
- OSTI ID:
- 5454788
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 108:10
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BIPYRIDINES
PHOTOLYSIS
EDTA
PYRAZINES
RUTHENIUM COMPLEXES
AQUEOUS SOLUTIONS
EXPERIMENTAL DATA
LASERS
LUMINESCENCE
PH VALUE
PHOTOCHEMISTRY
QUANTUM EFFICIENCY
RADIATIONLESS DECAY
RADICALS
AMINO ACIDS
AZINES
CARBOXYLIC ACIDS
CHELATING AGENTS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DATA
DE-EXCITATION
DECOMPOSITION
DISPERSIONS
EFFICIENCY
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
HETEROCYCLIC COMPOUNDS
INFORMATION
MIXTURES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PYRIDINES
SOLUTIONS
TRANSITION ELEMENT COMPLEXES
400500* - Photochemistry