Tris(2,2'-bipyridine)ruthenium(II)-sensitized photooxidation of phenols. Environmental effects on electron transfer yields and kinetics

Journal Article · Wed Dec 29 00:00:00 EST 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00390a012· OSTI ID:6203563

Miedlar, K; Das, P K

Laser flash photolysis (337.1 nm) combined with kinetic absorption-emission spectrophotometry has been used to study the photoreduction of tris(2,2'-bipyridine)ruthenium(II) by phenols and the effects of solvent, temperature, and ionic strength on electron transfer kinetics and yields. The excited-state quenching rate constants (k/sub q/) are in the range 1 x 10/sup 6/-5 x 10/sup 9/ M/sup -1/s/sup -1/ for substituted phenolate ions (pH 12.7) and correlate well with Hammett sigma/sup +/ values and with oxidation potentials. The plot of RT in k'/sub q/ against E/sub ArO./ArO/sup -// has a slope of -0.56, k'/sub q/ being the quenching rate constant corrected for the initial diffusional process. Arrhenius plots for k/sub q/ in the cases of p-CH/sub 3/O-C/sub 6/H/sub 4/O/sup -/, C/sub 6/H/sub 5/O/sup -/, and p-COO/sup -/-C/sub 6/H/sub 4/O/sup -/ as quenchers in aqueous solutions are linear from 0 to 80/sup 0/C. With p-methoxyphenolate ion and p-methoxy-N,N-dimethylaniline as quenchers, k/sub q/ increases on changing solvent from water to 95% ethanol or 95% acetone; k/sub q/ goes through a minimum at intermediate solvent compositions. Electron transfer yields (eta) are 0.3 to 1.0 for various phenolate ions in aqueous solutions (pH 12.7). For p-methoxyphenolate ion and p-methoxy-N,N-dimethylaniline, eta exhibits an increasing trend at elevated temperatures, in aqueous solvent systems richer in the nonaqueous component (acetone or ethanol), and at lower ionic strengths. The excited-state absorption spectrum (triplet-triplet) or tris(2,2'-bipyridine)ruthenium(II) in aqueous solution (230 to 800 nm) shows small absorption at (500 to 800 nm) and prominent three-band feature at 240 to 400 nm.

• Research Organization: Univ. of Notre Dame, IN
• OSTI ID: 6203563
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 104:26
• Country of Publication: United States
• Language: English

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37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
14 SOLAR ENERGY
BIPYRIDINES
PHOTOCHEMICAL REACTIONS
PHENOLS
OXIDATION
RUTHENIUM COMPLEXES
EXCITED STATES
REDUCTION
TRIPLETS
AQUEOUS SOLUTIONS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
LIGANDS
PHENOLATES
PHOTOCHEMICAL OXIDANTS
PHOTOLYSIS
QUANTITY RATIO
SODIUM NITRATES
SOLAR ENERGY CONVERSION
SOLVATION
TEMPERATURE EFFECTS
THERMODYNAMIC PROPERTIES
ALKALI METAL COMPOUNDS
AROMATICS
AZINES
CHEMICAL REACTIONS
COMPLEXES
CONVERSION
DECOMPOSITION
DISPERSIONS
ENERGY CONVERSION
ENERGY LEVELS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
KINETICS
MIXTURES
MULTIPLETS
NITRATES
NITROGEN COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PYRIDINES
REACTION KINETICS
SODIUM COMPOUNDS
SOLUTIONS
TRANSITION ELEMENT COMPLEXES
YIELDS
400500* - Photochemistry
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