title: Using Molecular Architecture to Control the Reactivity of a Triplet Vinylnitrene.
abstract: Photolysis of 3-azido-1-indenone (1) with a light-emitting diode (LED, λ = 405 nm) or mercury arc lamp (Pyrex) resulted in the formation of heterodimer 3 in excellent yield, through dimerization of triplet vinylnitrene32. At ambient temperature, vinylnitrene32 (λmaxat 340 and 480 nm) was detected directly with laser flash photolysis of vinyl azide 1. The vinylnitrene intermediate was also characterized directly with IR and ESR spectroscopy in cryogenic matrices. The ESR spectrum of vinylnitrene32 yielded a zero-field splitting parameter |D/hc| of 0.460 cm-1and |E/hc| of 0.015 cm-1, which reveals that vinylnitrene32 has significant 1,3-biradical character. The proposed mechanism for the formation and reactivity of triplet vinylnitrene32 was supported with density functional theory (DFT) calculations, which highlight that the steric demand of the five-membered ring in vinylnitrene32 prevents intersystem crossing to the corresponding azirine (10). CASSCF and CASPT2 calculations showed that the energy gap between the singlet and triplet configurations of vinylnitrene 2 is only 10 kcal/mol. In spite of this small energy gap, vinylnitrene32 does not decay by intersystem crossing, but rather by dimerization. Thus, triplet vinylnitrenes can be selectively formed with visible light and used to form new C-N bonds in synthetic applications.
authors: Department of Chemistry, University of Cincinnati , Cincinnati, Ohio 45221, United States.
authors: Sujan K
authors: SK
authors: Sarkar
authors: Department of Chemistry, University of Cincinnati , Cincinnati, Ohio 45221, United States.
authors: Onyinye
authors: O
authors: Osisioma
authors: Department of Chemistry and Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117, United States.
authors: William L
authors: WL
authors: Karney
authors: Department of Chemistry, Graduate School of Science, Hiroshima University , Hiroshima 739-8526, Japan.
authors: Manabu
authors: M
authors: Abe
authors: Department of Chemistry, University of Cincinnati , Cincinnati, Ohio 45221, United States.
authors: Anna D
authors: AD
authors: Gudmundsdottir