Photochemistry of 2-Naphthoyl Azide. An Ultrafast Time-Resolved UV鈥揤is and IR Spectroscopic and Computational Study

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• 作者：Jacek Kubicki ; Yunlong Zhang ; Shubham Vyas ; Gotard Burdzinski ; Hoi Ling Luk ; Jin Wang ; Jiadan Xue ; Huo-Lei Peng ; Elena A. Pritchina ; Michel Sliwa ; Guy Buntinx ; Nina P. Gritsan ; Christopher M. Hadad ; Matthew S. Platz
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：June 29, 2011
• 年：2011
• 卷：133
• 期：25
• 页码：9751-9761
• 全文大小：1058K
• 年卷期：v.133,no.25(June 29, 2011)
• ISSN：1520-5126

文摘

The photochemistry of 2-naphthoyl azide was studied in various solvents by femtosecond time-resolved transient absorption spectroscopy with IR and UV鈥搗is 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 (S₁) was observed by both time-resolved techniques. Three processes are involved in the decay of the S₁ excited state of 2-naphthoyl azide: intersystem crossing, singlet nitrene formation, and isocyanate formation. The lifetime of the S₁ state decreases significantly as the solvent polarity increases. In all solvents studied, isocyanate formation correlates with the decay of the azide S₁ state. Nitrene formation correlates with the decay of the relaxed S₁ state only upon 350 nm excitation (S₀ 鈫?S₁ excitation). When S_n (n 鈮?2) states are populated upon excitation (位_ex = 270 nm), most nitrene formation takes place within a few picoseconds through the hot S₁ 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 S₁ 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.