meta and para substitution effects on the electronic state energies and ring-expansion reactivities of phenylnitrenes

William T.G. Johnson, Michael B. Sullivan, Christopher J. Cramer

Research output: Contribution to journalConference articlepeer-review

72 Scopus citations

Abstract

The electronic structures of the triplet ground states and first three excited singlet states for phenylnitrene, 14 meta-, and 17 para-substituted congeners have been characterized using density functional theory and multireference second-order perturbation theory (CASPT2). Ring expansion pathways to form didehydroazepines have activation enthalpies of about 9 kcal · mol-1 and are fairly insensitive to substitution - in the case of the strongest para donor, MeNH-, this barrier increases to about 13 kcal · mol-1. The trends in state energies as a function of substitution are rationalized using a (2,2) configuration interaction theory and qualitative molecular orbital theory. Analysis of spin-orbit coupling in the nitrenes using the same model in conjunction with explicit calculation of spin-orbit coupling matrix elements rationalizes why electron donating substituents increase rates of intersystem crossing.

Original languageEnglish (US)
Pages (from-to)492-508
Number of pages17
JournalInternational Journal of Quantum Chemistry
Volume85
Issue number4-5
DOIs
StatePublished - Nov 15 2001
EventInternational Symposium on Atomic, Molecular and Condensed Matter Theory - St.Augustine, FL, United States
Duration: Feb 24 2001Mar 2 2001

Keywords

  • Configuration interaction
  • Density functional theory
  • Excited states
  • Nitrene didehydroazepine
  • Photoaffinity labels
  • Photochemistry
  • Ring expansion

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