Reactivity and intersystem crossing of singlet methylene in solution

Nicholas J. Turro, Yuan Cha, Ian Gould

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Evidence is reported which demonstrates that singlet methylene, produced from the photolysis of diazomethane or diazirine, undergoes intersystem crossing to form triplet methylene in perfluorohexane solvent. The results of triplet sensitized photolysis and of direct photolysis experiments with dilute concentrations of substrate (cis- and trans-2-pentene and chloroform) appear to be essentially identical. Stern-Volmer analyses of the competition kinetics between acetonitrile and 2-pentenes or chloroform for singlet methylene are consistent with the near diffusion controlled reactivity of singlet methylene. With the assumption of diffusion-controlled reactions for singlet methylene, plots of the quantum yield for singlet vs. triplet reaction for methylene allow the first estimate (≤8 × 108 s-1) of the rate of intersystem crossing of singlet methylene in the condensed phase. This value is considerably smaller than the value that is extrapolated to the solution phase from results in the gas phase. The possible reasons for this difference are discussed.

Original languageEnglish (US)
Pages (from-to)2101-2107
Number of pages7
JournalJournal of the American Chemical Society
Volume109
Issue number7
StatePublished - 1987
Externally publishedYes

Fingerprint

Photolysis
Diazomethane
Alkenes
Chloroform
Chlorine compounds
Quantum yield
Acetonitrile
Gases
Kinetics
Substrates
Experiments

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Reactivity and intersystem crossing of singlet methylene in solution. / Turro, Nicholas J.; Cha, Yuan; Gould, Ian.

In: Journal of the American Chemical Society, Vol. 109, No. 7, 1987, p. 2101-2107.

Research output: Contribution to journalArticle

@article{60053e4b917f4778ac1896b06102f6f9,
title = "Reactivity and intersystem crossing of singlet methylene in solution",
abstract = "Evidence is reported which demonstrates that singlet methylene, produced from the photolysis of diazomethane or diazirine, undergoes intersystem crossing to form triplet methylene in perfluorohexane solvent. The results of triplet sensitized photolysis and of direct photolysis experiments with dilute concentrations of substrate (cis- and trans-2-pentene and chloroform) appear to be essentially identical. Stern-Volmer analyses of the competition kinetics between acetonitrile and 2-pentenes or chloroform for singlet methylene are consistent with the near diffusion controlled reactivity of singlet methylene. With the assumption of diffusion-controlled reactions for singlet methylene, plots of the quantum yield for singlet vs. triplet reaction for methylene allow the first estimate (≤8 × 108 s-1) of the rate of intersystem crossing of singlet methylene in the condensed phase. This value is considerably smaller than the value that is extrapolated to the solution phase from results in the gas phase. The possible reasons for this difference are discussed.",
author = "Turro, {Nicholas J.} and Yuan Cha and Ian Gould",
year = "1987",
language = "English (US)",
volume = "109",
pages = "2101--2107",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "7",

}

TY - JOUR

T1 - Reactivity and intersystem crossing of singlet methylene in solution

AU - Turro, Nicholas J.

AU - Cha, Yuan

AU - Gould, Ian

PY - 1987

Y1 - 1987

N2 - Evidence is reported which demonstrates that singlet methylene, produced from the photolysis of diazomethane or diazirine, undergoes intersystem crossing to form triplet methylene in perfluorohexane solvent. The results of triplet sensitized photolysis and of direct photolysis experiments with dilute concentrations of substrate (cis- and trans-2-pentene and chloroform) appear to be essentially identical. Stern-Volmer analyses of the competition kinetics between acetonitrile and 2-pentenes or chloroform for singlet methylene are consistent with the near diffusion controlled reactivity of singlet methylene. With the assumption of diffusion-controlled reactions for singlet methylene, plots of the quantum yield for singlet vs. triplet reaction for methylene allow the first estimate (≤8 × 108 s-1) of the rate of intersystem crossing of singlet methylene in the condensed phase. This value is considerably smaller than the value that is extrapolated to the solution phase from results in the gas phase. The possible reasons for this difference are discussed.

AB - Evidence is reported which demonstrates that singlet methylene, produced from the photolysis of diazomethane or diazirine, undergoes intersystem crossing to form triplet methylene in perfluorohexane solvent. The results of triplet sensitized photolysis and of direct photolysis experiments with dilute concentrations of substrate (cis- and trans-2-pentene and chloroform) appear to be essentially identical. Stern-Volmer analyses of the competition kinetics between acetonitrile and 2-pentenes or chloroform for singlet methylene are consistent with the near diffusion controlled reactivity of singlet methylene. With the assumption of diffusion-controlled reactions for singlet methylene, plots of the quantum yield for singlet vs. triplet reaction for methylene allow the first estimate (≤8 × 108 s-1) of the rate of intersystem crossing of singlet methylene in the condensed phase. This value is considerably smaller than the value that is extrapolated to the solution phase from results in the gas phase. The possible reasons for this difference are discussed.

UR - http://www.scopus.com/inward/record.url?scp=0001058026&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001058026&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0001058026

VL - 109

SP - 2101

EP - 2107

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 7

ER -