中文摘要：

获取了1-甲基胸腺嘧啶（MT）涵盖紫外光谱中A带和B带吸收的共5个激发波长的共振拉曼光谱,并结合密度泛函理论方法研究了MT的电子激发和Franck-Condon区域结构动力学.在TD-B3LYP/6-311＋＋G（d,p）计算水平下,A带和B带吸收被分别指认为πH→πL＊/πH-2→π＊L＋2和πH→π＊L＋2/πH-2→πL＊跃迁.甲基参与嘧啶环的共轭使MT的A带最大吸收波长λmax相对于胸腺嘧啶（T）发生明显红移,并对Franck-Condon区域的动态结构产生一定影响.A带和B带共振拉曼光谱分别被指认为14个振动模式和11个振动模式的基频、泛频和组合频.C5=C6伸缩＋C6H12面内弯曲振动ν9,环变形振动ν16和N3C2N1反对称伸缩＋C4C5C10反对称伸缩振动ν18占据了A带共振拉曼光谱强度的绝大部分.这表明1πHπL＊激发态结构动力学主要沿这些反应坐标展开.考察了溶剂对共振拉曼光谱的影响,结果表明,C4=O9伸缩＋N3H11面内弯曲振动ν8的活性与溶剂性质有关,其激发态位移量随溶剂性质的变化规律与胸腺嘧啶一致.

英文摘要：

Resonance Raman spectra at five excitations covering the A- and B-band absorptions of 1-methylthymine （MT） were acquired. The Franck-Condon region structural dynamics and electronic transitions of MT were studied in conjunction with density functional theory calculations. The A- and B-band absorptions are assigned as πH→πL＊/πH-2→π＊L＋2和πH→π＊L＋2/πH-2→πL＊ transitions, respectively, using the B3LYP/6-311 ＋ G（d,p） level of theory. The hyper-conjugation interaction between the CH3 group and pyrimidine ring leads to a noticeable red-shift in Amax of the A-band absorption for MT, relative to that for thymine. It also significantly affects the Franck-Condon region structural dynamics of MT. The A- and B-band resonance Raman spectra are respectively assigned as the 14 and 11 fundamentals, their overtones and combination bands. The A-band resonance Raman intensities of MT are dominated by the v9 （C5=C6 stretching ＋ G6H12 in-plane bending）, v16 （ring deformation）, and v18 （N3C2N1 asymmetric stretching＋C4C5C10 asymmetric stretching） modes. This indicates that the structural dynamics of MT are mainly along these reaction coordinates. The effect of solvent on the structural dynamics was examined. The Raman activity of the v8 （C4=O9 stretching ＋ N3H11 in-plane bending） vibrational mode is tuned by solvent, and the dependence of the normal mode displacement of v8 on solvent is similar to that for thymine.