Mesolytic scission of C-C bonds as a probe for photoinduced electron transfer reactions of Quinones

Przemyslaw Maslak, William H. Chapman

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Photoinduced electron transfer reactions of chlorinated benzoquinones are investigated using bibenzylic donors that undergo rapid fragmentation upon oxidation. The fragmentation rates and the quantum yields are used to probe the dynamics of back-electron transfer (BET) in two types of radical ion pairs. The triplet ion pairs formed by interception of excited state quinones give products with high quantum yields. The singlet ion pairs formed by irradiation of the charge-transfer (CT) complexes between the quinones and the donors undergo reactions with significantly lower efficiency. The advantage of the first method (triplet quenching) over the CT-irradiation depends on the energetics of BET. It is large for reactions with relatively small ΔGet for BET and it decreases for reactions with more negative ΔGbet. The indirectly obtained rates of BET are in excellent agreement with literature data for similar, but unreactive systems, and the rates of C-C bond scission in radical cations generated in these systems are consistent with the thermodynamics of these processes.

Original languageEnglish (US)
Pages (from-to)2647-2656
Number of pages10
JournalJournal of Organic Chemistry
Volume61
Issue number8
DOIs
StatePublished - Apr 19 1996

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Quinones
Electrons
Quantum yield
Ions
Charge transfer
Benzoquinones
Irradiation
Excited states
Cations
Quenching
Thermodynamics
Oxidation

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

Cite this

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title = "Mesolytic scission of C-C bonds as a probe for photoinduced electron transfer reactions of Quinones",
abstract = "Photoinduced electron transfer reactions of chlorinated benzoquinones are investigated using bibenzylic donors that undergo rapid fragmentation upon oxidation. The fragmentation rates and the quantum yields are used to probe the dynamics of back-electron transfer (BET) in two types of radical ion pairs. The triplet ion pairs formed by interception of excited state quinones give products with high quantum yields. The singlet ion pairs formed by irradiation of the charge-transfer (CT) complexes between the quinones and the donors undergo reactions with significantly lower efficiency. The advantage of the first method (triplet quenching) over the CT-irradiation depends on the energetics of BET. It is large for reactions with relatively small ΔGet for BET and it decreases for reactions with more negative ΔGbet. The indirectly obtained rates of BET are in excellent agreement with literature data for similar, but unreactive systems, and the rates of C-C bond scission in radical cations generated in these systems are consistent with the thermodynamics of these processes.",
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Mesolytic scission of C-C bonds as a probe for photoinduced electron transfer reactions of Quinones. / Maslak, Przemyslaw; Chapman, William H.

In: Journal of Organic Chemistry, Vol. 61, No. 8, 19.04.1996, p. 2647-2656.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Mesolytic scission of C-C bonds as a probe for photoinduced electron transfer reactions of Quinones

AU - Maslak, Przemyslaw

AU - Chapman, William H.

PY - 1996/4/19

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N2 - Photoinduced electron transfer reactions of chlorinated benzoquinones are investigated using bibenzylic donors that undergo rapid fragmentation upon oxidation. The fragmentation rates and the quantum yields are used to probe the dynamics of back-electron transfer (BET) in two types of radical ion pairs. The triplet ion pairs formed by interception of excited state quinones give products with high quantum yields. The singlet ion pairs formed by irradiation of the charge-transfer (CT) complexes between the quinones and the donors undergo reactions with significantly lower efficiency. The advantage of the first method (triplet quenching) over the CT-irradiation depends on the energetics of BET. It is large for reactions with relatively small ΔGet for BET and it decreases for reactions with more negative ΔGbet. The indirectly obtained rates of BET are in excellent agreement with literature data for similar, but unreactive systems, and the rates of C-C bond scission in radical cations generated in these systems are consistent with the thermodynamics of these processes.

AB - Photoinduced electron transfer reactions of chlorinated benzoquinones are investigated using bibenzylic donors that undergo rapid fragmentation upon oxidation. The fragmentation rates and the quantum yields are used to probe the dynamics of back-electron transfer (BET) in two types of radical ion pairs. The triplet ion pairs formed by interception of excited state quinones give products with high quantum yields. The singlet ion pairs formed by irradiation of the charge-transfer (CT) complexes between the quinones and the donors undergo reactions with significantly lower efficiency. The advantage of the first method (triplet quenching) over the CT-irradiation depends on the energetics of BET. It is large for reactions with relatively small ΔGet for BET and it decreases for reactions with more negative ΔGbet. The indirectly obtained rates of BET are in excellent agreement with literature data for similar, but unreactive systems, and the rates of C-C bond scission in radical cations generated in these systems are consistent with the thermodynamics of these processes.

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