4-硝基咪唑A-带激发态结构动力学

通过共振拉曼光谱实验和量子化学计算的方法研究了4-硝基咪唑(4NI)A-带激发态衰变动力学. 对4NI的振动光谱、紫外电子吸收光谱、荧光光谱和共振拉曼光谱进行了指认. 在全活化空间自洽场法(CASSCF)/6-31G(d)计算水平下获得了单重激发态S₁(n_Oπ^*)和S₂(ππ^*)和势能面交叉点S₁(n_Oπ^*)/S₂(ππ^*)的优化几何结构和能量, 分析了A-带共振拉曼光谱的强度模式特征, 获得了短时结构动力学, 并结合全活化空间自洽场法(CASSCF)理论计算结果确定了4NI 在S₂(ππ^*)态衰变通道主要是S_{2, FC}→S_{2, min}(ππ^*)→S₀辐射弛豫.

Excited State Structural Dynamics of A-Band of 4-Nitroimidazole

The A-band structural dynamics of 4-nitroimidazole (4NI) were studied using resonance Raman spectroscopy and quantum mechanical calculations, and the vibrational spectra, UV absorption spectra, fluorescence spectra, and A-band resonance Raman spectra were assigned. The resonance Raman spectra of 4-nitroimidazole were obtained in methanol with excitation wavelengths in resonance with the first intense absorption band, to probe the short-time structural dynamics. The optimized geometric structures and the excitation energies of the singlet excited states S₁(n_Oπ^*) and S₂(ππ^*), and the conical intersection point S₁(n_Oπ^*)/S₂(ππ^*), were computed at the complete active space self-consistent field (CASSCF)/6-31G(d) theory level. The intensity patterns of the A-band resonance Raman spectra were analyzed, and the results, together with those of the CASSCF calculations, revealed that the major decay channel initiated from the S₂(ππ^*) state was S_{2, FC}→S_{2, min}(ππ^*)→S₀ radiation.