title: Photochemistry of 2-naphthoyl azide. An ultrafast time-resolved UV-vis and IR spectroscopic and computational study.
abstract: The photochemistry of 2-naphthoyl azide was studied in various solvents by femtosecond time-resolved transient absorption spectroscopy with IR and UV-vis detection. The experimental findings were interpreted with the aid of computational studies. Using polar and nonpolar solvents, the formation and decay of the first singlet excited state (S(1)) was observed by both time-resolved techniques. Three processes are involved in the decay of the S(1) excited state of 2-naphthoyl azide: intersystem crossing, singlet nitrene formation, and isocyanate formation. The lifetime of the S(1) state decreases significantly as the solvent polarity increases. In all solvents studied, isocyanate formation correlates with the decay of the azide S(1) state. Nitrene formation correlates with the decay of the relaxed S(1) state only upon 350 nm excitation (S(0) → S(1) excitation). When S(n) (n ≥ 2) states are populated upon excitation (λ(ex) = 270 nm), most nitrene formation takes place within a few picoseconds through the hot S(1) and higher singlet excited states (S(n)) of 2-naphthoyl azide. The data correlate with the results of electron density difference calculations that predict nitrene formation from the higher-energy singlet excited states, in addition to the S(1) state. For all of these experiments, no recovery of the ground state was observed up to 3 ns after photolysis, which indicates that both internal conversion and fluorescence have very low efficiencies.
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: Yunlong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shubham
authors.initials: S
authors.lastname: Vyas
authors.forename: Gotard
authors.initials: G
authors.lastname: Burdzinski
authors.forename: Hoi Ling
authors.initials: HL
authors.lastname: Luk
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.forename: Jiadan
authors.initials: J
authors.lastname: Xue
authors.forename: Huo-Lei
authors.initials: HL
authors.lastname: Peng
authors.forename: Elena A
authors.initials: EA
authors.lastname: Pritchina
authors.forename: Michel
authors.initials: M
authors.lastname: Sliwa
authors.forename: Guy
authors.initials: G
authors.lastname: Buntinx
authors.forename: Nina P
authors.initials: NP
authors.lastname: Gritsan
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Hadad
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Platz