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Study of the Chemistry of ortho- and para-Biphenylnitrenes by Laser Flash Photolysis and Time-Resolved IR Experiments and by B3LYP and CASPT2 Calculations

TSAO, Meng-Lin ; GRITSAN, Nina ; JAMES, Tammi R. ; PLATZ, Matthew S. ; HROVAT, David A. ; BORDEN, Weston Thatcher

Journal of the American Chemical Society, 2003-08, Vol.125 (31), p.9343-9358 [Periódico revisado por pares]

Washington, DC: American Chemical Society

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  • Título:
    Study of the Chemistry of ortho- and para-Biphenylnitrenes by Laser Flash Photolysis and Time-Resolved IR Experiments and by B3LYP and CASPT2 Calculations
  • Autor: TSAO, Meng-Lin ; GRITSAN, Nina ; JAMES, Tammi R. ; PLATZ, Matthew S. ; HROVAT, David A. ; BORDEN, Weston Thatcher
  • É parte de: Journal of the American Chemical Society, 2003-08, Vol.125 (31), p.9343-9358
  • Notas: ark:/67375/TPS-MCV31WBW-K
    istex:A546B809497E689A230B744FCF1199E0FACBC4FA
    ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
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  • Descrição: The photochemistry of ortho-biphenyl azide (1a) has been studied by laser flash photolysis (LFP), with UV-vis and IR detection of the transient intermediates formed. LFP (266 nm) of 1a in glassy 3-methylpentane at 77 K releases singlet ortho-biphenylnitrene (1b) (lambda(max) = 410 nm, tau = 59 +/- 6 ns), which under these conditions decays cleanly to the lower energy triplet state. In fluid solution at 298 K, 1b rapidly (tau < 10 ns) partitions between formation of isocarbazole (4) (lambda(max) = 430 nm, tau = 70 ns) and benzazirine (1e) (lambda(max) = 305 nm, tau = 12 ns). Isocarbazole 4 undergoes a 1,5-hydrogen shift, with k(H)/k(D) = 3.4 at 298 K to form carbazole 9 and smaller amounts of two other isocarbazoles (7 and 8). Benzazirine 1e ring-opens reversibly to azacycloheptatetraene (1f), which serves as a reservoir for singlet nitrene 1b. Azacycloheptatetraene 1f ultimately forms carbazole 9 on the millisecond time scale by the pathway 1f --> 1e --> 1b --> 4 --> 9. The energies of the transient intermediates and of the transition structures connecting them were successfully predicted by CASPT2/6-31G calculations. The electronic and vibrational spectra of the intermediates, computed by density functional theory, support the assignment of the transient spectra, observed in the formation of 9 from 1a.
  • Editor: Washington, DC: American Chemical Society
  • Idioma: Inglês;Russo
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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