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 language | English (US) |
---|---|
Pages (from-to) | 492-508 |
Number of pages | 17 |
Journal | International Journal of Quantum Chemistry |
Volume | 85 |
Issue number | 4-5 |
DOIs | |
State | Published - Nov 15 2001 |
Event | International Symposium on Atomic, Molecular and Condensed Matter Theory - St.Augustine, FL, United States Duration: Feb 24 2001 → Mar 2 2001 |
Keywords
- Configuration interaction
- Density functional theory
- Excited states
- Nitrene didehydroazepine
- Photoaffinity labels
- Photochemistry
- Ring expansion