title: Direct observation of a sulfonyl azide excited state and its decay processes by ultrafast time-resolved IR spectroscopy.
abstract: The photochemistry of 2-naphthylsulfonyl azide (2-NpSO(2)N(3)) was studied by femtosecond time-resolved infrared (TR-IR) spectroscopy and with quantum chemical calculations. Photolysis of 2-NpSO(2)N(3) with 330 nm light promotes 2-NpSO(2)N(3) to its S(1) state. The S(1) excited state has a prominent azide vibrational band. This is the first direct observation of the S(1) state of a sulfonyl azide, and this vibrational feature allows a mechanistic study of its decay processes. The S(1) state decays to produce the singlet nitrene. Evidence for the formation of the pseudo-Curtius rearrangement product (2-NpNSO(2)) was inconclusive. The singlet sulfonylnitrene (1)(2-NpSO(2)N) is a short-lived species (τ ≈ 700 ± 300 ps in CCl(4)) that decays to the lower-energy and longer-lived triplet nitrene (3)(2-NpSO(2)N). Internal conversion of the S(1) excited state to the ground state S(0) is an efficient deactivation process. Intersystem crossing of the S(1) excited state to the azide triplet state contributes only modestly to deactivation of the S(1) state of 2-NpSO(2)N(3).
authors.affiliation: Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Kubicki
authors.forename: Hoi Ling
authors.initials: HL
authors.lastname: Luk
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shubham
authors.initials: S
authors.lastname: Vyas
authors.forename: Huo-Lei
authors.initials: HL
authors.lastname: Peng
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Hadad
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Platz
mesh_terms: D001386:Azides / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013450:Sulfones / Q000737:chemistry*; D013997:Time Factors
chemical_list: D001386:Azides; D013450:Sulfones