Li Ming-Juan, Liu Ming-Xia, Zhao Yan-Ying, Pei Ke-Mei, Wang Hui-Gang, Zheng Xuming, Fang Wei Hai
Department of Chemistry and Key Laboratory of Advanced Textiles Material and Manufacture Technology, MOE, Zhejiang Sci-Tech University , Hangzhou, Zhejiang Province, 310023, People's Republic of China.
J Phys Chem B. 2013 Oct 3;117(39):11660-9. doi: 10.1021/jp403798d. Epub 2013 Sep 11.
The resonance Raman spectroscopic study of the excited state structural dynamics of 1,3-dimethyluracil (DMU), 5-bromo-1,3-dimethyluracil (5BrDMU), uracil, and thymine in water and acetonitrile were reported. Density functional theory calculations were carried out to help elucidate the ultraviolet electronic transitions associated with the A-, and B-band absorptions and the vibrational assignments of the resonance Raman spectra. The effect of the methylation at N1, N3 and C5 sites of pyrimidine ring on the structural dynamics of uracils in different solvents were explored on the basis of the resonance Raman intensity patterns. The relative resonance Raman intensities of DMU and 5BrDMU are computed at the B3LYP-TD level. Huge discrepancies between the experimental resonance Raman intensities and the B3LYP-TD predicted ones were observed. The underlying mechanism was briefly discussed. The decay channel through the S1((1)nπ*)/S2((1)ππ*) conical intersection and the S1((1)nπ*)/T1((3)ππ*) intersystem crossing were revealed by using the CASSCF(8,7)/6-31G(d) level of theory calculations.
报道了对1,3 - 二甲基尿嘧啶（DMU）、5 - 溴 - 1,3 - 二甲基尿嘧啶（5BrDMU）、尿嘧啶和胸腺嘧啶在水和乙腈中的激发态结构动力学进行的共振拉曼光谱研究。进行了密度泛函理论计算，以帮助阐明与A - 带和B - 带吸收相关的紫外电子跃迁以及共振拉曼光谱的振动归属。基于共振拉曼强度模式，探讨了嘧啶环上N1、N3和C5位点甲基化对不同溶剂中尿嘧啶结构动力学的影响。在B3LYP - TD水平上计算了DMU和5BrDMU的相对共振拉曼强度。观察到实验共振拉曼强度与B3LYP - TD预测强度之间存在巨大差异。简要讨论了其潜在机制。通过使用CASSCF(8,7)/6 - 31G(d)理论计算水平揭示了通过S1((1)nπ*)/S2((1)ππ*)锥形交叉和S1((1)nπ*)/T1((3)ππ*)系间窜越的衰变通道。
