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[摘要]：Photochemical isomerization of 3-piperidino-1,2-benzisothiazole (BIT) benzothiazole (BT) was investigated. In particular, the effect of nitro-substitution on the benzene ring was selectively examined for the parent, 5-nitro-, and 7-nitro-derivatives. 3-Piperidino-BIT and nitro-3-piperidino-BIT isomerized irreversibly to the corresponding 2-piperidino-BT, and this reaction mechanism was investigated using density-functional theory (DFT) and time-dependent (TD)-DFT calculations. These calculations showed that this isomerization goes through an azirine intermediate. In addition, excitation wavelength effect demonstrates that isomerization occurs from the upper excited state of nitro-derivatives. The HOMO-LUMO transition has charge-transfer and photoinactive characters. |
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