Coupled electron-proton transfer in interactions of triplet C60 with hydrogen-bonded phenols

Effects of solvation, deuteration, and redox potentials

L. Biczók, Neeraj Gupta, Henry Linschitz

Research output: Contribution to journalArticle

97 Citations (Scopus)

Abstract

The quenching of triplet C60 by phenols is greatly enhanced by addition of pyridines, which also lower the phenol voltammetric oxidation potentials. Flash photolysis shows that the products of this-quenching reaction are the C60·- anion radical, neutral phenoxy (or naphthoxy) radicals, and protonated pyridines. Analysis of the second-order kinetics gives quenching rate constants and values of formation constants of hydrogen- bonded phenol-pyridine pairs. The latter agree with those derived from absorption spectra over a wide range of phenols, pyridines, and solvents. Significant deuterium kinetic isotope effects are observed, indicating the importance of both proton transfer and hydrogen bonding in enhancing the rate. Quenching rates and radical yields both increase with solvent polarity. It is concluded that this quenching process involves interaction between 3C60 and a hydrogen-bonded phenol-pyridine complex, in which electron transfer from the phenol to 3C60 is concerted with proton transfer from phenol to hydrogen-bonded pyridine.

Original languageEnglish
Pages (from-to)12601-12609
Number of pages9
JournalJournal of the American Chemical Society
Volume119
Issue number51
DOIs
Publication statusPublished - Dec 24 1997

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Proton transfer
Phenols
Solvation
Phenol
Oxidation-Reduction
Protons
Hydrogen
Quenching
Pyridines
Pyridine
Electrons
Kinetics
Deuterium
Photolysis
Hydrogen Bonding
Isotopes
Anions
Absorption spectra
Rate constants
Hydrogen bonds

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Coupled electron-proton transfer in interactions of triplet C60 with hydrogen-bonded phenols : Effects of solvation, deuteration, and redox potentials. / Biczók, L.; Gupta, Neeraj; Linschitz, Henry.

In: Journal of the American Chemical Society, Vol. 119, No. 51, 24.12.1997, p. 12601-12609.

Research output: Contribution to journalArticle

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N2 - The quenching of triplet C60 by phenols is greatly enhanced by addition of pyridines, which also lower the phenol voltammetric oxidation potentials. Flash photolysis shows that the products of this-quenching reaction are the C60·- anion radical, neutral phenoxy (or naphthoxy) radicals, and protonated pyridines. Analysis of the second-order kinetics gives quenching rate constants and values of formation constants of hydrogen- bonded phenol-pyridine pairs. The latter agree with those derived from absorption spectra over a wide range of phenols, pyridines, and solvents. Significant deuterium kinetic isotope effects are observed, indicating the importance of both proton transfer and hydrogen bonding in enhancing the rate. Quenching rates and radical yields both increase with solvent polarity. It is concluded that this quenching process involves interaction between 3C60 and a hydrogen-bonded phenol-pyridine complex, in which electron transfer from the phenol to 3C60 is concerted with proton transfer from phenol to hydrogen-bonded pyridine.

AB - The quenching of triplet C60 by phenols is greatly enhanced by addition of pyridines, which also lower the phenol voltammetric oxidation potentials. Flash photolysis shows that the products of this-quenching reaction are the C60·- anion radical, neutral phenoxy (or naphthoxy) radicals, and protonated pyridines. Analysis of the second-order kinetics gives quenching rate constants and values of formation constants of hydrogen- bonded phenol-pyridine pairs. The latter agree with those derived from absorption spectra over a wide range of phenols, pyridines, and solvents. Significant deuterium kinetic isotope effects are observed, indicating the importance of both proton transfer and hydrogen bonding in enhancing the rate. Quenching rates and radical yields both increase with solvent polarity. It is concluded that this quenching process involves interaction between 3C60 and a hydrogen-bonded phenol-pyridine complex, in which electron transfer from the phenol to 3C60 is concerted with proton transfer from phenol to hydrogen-bonded pyridine.

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