Interactions of formate ion with triplets of anthraquinone-2-sulfonate, 1,4-naphthoquinone, benzophenone-4-carboxylate, and benzophenone-4-sulfonate

Journal Article · Thu May 30 00:00:00 EDT 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100164a048· OSTI ID:5987958

Loeff, I; Goldstein, S; Treinin, A ^[1]; Linschitz, H ^[2]

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1. Hebrew Univ., Jerusalem (Israel)
2. Brandeis Univ., Waltham, MA (United States)

The interaction of formate with the triplet states of naphthoquinone (NQ), anthraquinone-2-sulfonate (AQS), benzophenone-4-carboxylate (BC), and benzophenone-4-sulfonate (BS) was studied by laser flash photolysis. Rate constants were determined either by direct measurement of triplet lifetimes or by inhibition of product yields by competitive reactants. Radical products are formed in two stages, direct reduction by formate and efficient secondary reduction by initially formed CO{sub 2}{sup {sm bullet}{minus}} radicals. The quinones react by electron transfer with quenching rate constants k{sub q}(NQ) = 3 {times} 10{sup 9} and k{sub q}(AQS) = 4 {times} 10{sup 8} M{sup {minus}1} s{sup {minus}1}, giving anion radicals with primary yields of {phi}{sub R}(NQ) {approximately} 0.7 and {phi}{sub R}(AQS) {approximately} 0.3. Formic acid quenches {sup 3}AQS much more slowly. The less strongly oxidizing ketone triplets react by H-atom abstraction, k{sub q}(BC) = 1.3 {times} 10{sup 7} and k{sub q}(BS) = 5.3 {times} 10{sup 7} M{sup {minus}1} s{sup {minus}1}, giving protonated ketyl radicals with primary yields {phi}{sub R} {approximately} 0.7. Photoreduction of BC exhibits a deuterium isotope effect, k{sub H}/k{sub D} = 1.6, whereas AQS shows none. A new, short-lived transient, E, is observed in the {sup 3}AQS-formate reaction, which may be an exciplex or adduct. The redox potential, E{degree}{prime}(NQ/NQ{sup {sm bullet}{minus}}) = {minus}0.12 V, and rate constants for radical reactions of NQ and O{sub 2} were measured by pulse radiolysis. The results are discussed in terms of pertinent redox potentials, bond strengths, and the nature of the exciplex intermediates.

• OSTI ID: 5987958
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 95:11; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBOXYLIC ACID SALTS
CHEMICAL REACTIONS
FORMATES
QUINONES
SULFONATES
ABSORPTION SPECTROSCOPY
ANIONS
ANTHRAQUINONES
BENZOPHENONE
CHEMICAL REACTION KINETICS
ELECTRON TRANSFER
ELECTRONIC STRUCTURE
EXCITED STATES
EXPERIMENTAL DATA
ISOTOPIC EXCHANGE
LASER RADIATION
PHOTOCHEMISTRY
PHOTOLYSIS
RADICALS
RADIOLYSIS
REDUCTION
RESONANCE
TIME DEPENDENCE
AROMATICS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMISTRY
DATA
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENERGY LEVELS
INFORMATION
IONS
KETONES
KINETICS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PHOTOCHEMICAL REACTIONS
RADIATION EFFECTS
RADIATIONS
REACTION KINETICS
SPECTROSCOPY
140505* - Solar Energy Conversion- Photochemical
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& Thermochemical Conversion- (1980-)
400201 - Chemical & Physicochemical Properties