Photodynamics of the tris(2,2'-bipyrazine)ruthenium(2+)/methylviologen/EDTA system in aqueous solution

Journal Article · Wed May 14 04:00:00 EDT 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00270a013· OSTI ID:5454788

Prasad, D R; Hoffman, M Z

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), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:10; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
AMINO ACIDS
AQUEOUS SOLUTIONS
AZINES
BIPYRIDINES
CARBOXYLIC ACIDS
CHELATING AGENTS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DATA
DE-EXCITATION
DECOMPOSITION
DISPERSIONS
EDTA
EFFICIENCY
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
INFORMATION
LASERS
LUMINESCENCE
MIXTURES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PH VALUE
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PHOTOLYSIS
PYRAZINES
PYRIDINES
QUANTUM EFFICIENCY
RADIATIONLESS DECAY
RADICALS
RUTHENIUM COMPLEXES
SOLUTIONS
TRANSITION ELEMENT COMPLEXES