Matrix-Isolation Decay Kinetics of Triplet Cyclobutanediyls. Observation of Both Arrhenius Behavior and Heavy-Atom Tunneling in C—C Bond-Forming Reactions

Michael B. Sponsler, Rakesh Jain, Frank D. Corns, Dennis A. Dougherty

Research output: Contribution to journalArticle

51 Scopus citations

Abstract

The ring-closure reactions of a variety of triplet 1,3-cyclobutanediyls (1) have been observed by EPR spectroscopy under matrix-isolation conditions. It is shown that matrix-site effects can be very well modeled by a Gaussian distribution of activation energies with a standard deviation of ca. 0.5 kcal/mol. Several new techniques have been developed to model such dispersive kinetics. Structures 1 with delocalizing substituents (vinyl, phenyl) show conventional Arrhenius behavior, with log A = 6–8 and Ea = 1–2 kcal/mol. Fully localized cyclobutanediyls ring close via quantum mechanical tunneling. A model emphasizing the differing well depths of the singlet biradicals is developed to rationalize these contrasting behaviors.

Original languageEnglish (US)
Pages (from-to)2240-2252
Number of pages13
JournalJournal of the American Chemical Society
Volume111
Issue number6
DOIs
StatePublished - Mar 1989
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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