物理化学学报 >> 2009, Vol. 25 >> Issue (09): 1799-1805.doi: 10.3866/PKU.WHXB20090825

研究论文 上一篇    下一篇

尿嘧啶和5-氯尿嘧啶1S01S2跃迁动态结构的共振拉曼光谱

翁克凤, 王惠钢, 祝新明, 郑旭明   

  1. 浙江理工大学化学系, 先进纺织材料与加工技术教育部重点实验室, 杭州 310018
  • 收稿日期:2009-02-12 修回日期:2009-05-16 发布日期:2009-09-03
  • 通讯作者: 郑旭明 E-mail:zxm@zstu.edu.cn

Resonance Raman Spectra of Uracil and 5-Chlorouracil Dynamic Structures during 1S01S2 Transition

WENG Ke-Feng, WANG Hui-Gang, ZHU Xin-Ming, ZHENG Xu-Ming   

  1. Key Laboratory of Adavanced Textile Materials and Manufacturing Technology of the Ministry of Education, Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China
  • Received:2009-02-12 Revised:2009-05-16 Published:2009-09-03
  • Contact: ZHENG Xu-Ming E-mail:zxm@zstu.edu.cn

摘要:

采用含时量子波包理论的简单模型对5-氯尿嘧啶和尿嘧啶的共振拉曼光谱开展了强度分析拟合, 获得了1(π, π*)激发态的几何结构变化动态特征. 结果表明, 尿嘧啶1S0→1S2跃迁的动态结构特征因5-位氯原子取代而改变. 5-氯尿嘧啶的动态结构特征主要沿C5=C6伸缩振动+C6H12 弯曲振动和N3H9/N1H7弯曲振动+N1C6伸缩振动反应坐标展开, 而尿嘧啶的动态结构特征主要沿嘧啶环的伸缩振动+C5H11/C6H12/N1H7弯曲振动和C4=O10伸缩振动反应坐标展开. π和π*轨道中氯原子的pz电子参与嘧啶环的p-π共轭作用导致了在1(π, π*)激发态上5-氯尿嘧啶的振动重组能更多地配分给嘧啶环的弯曲振动模式和C5=C6伸缩振动模式. 尿嘧啶在甲醇中的激发态动态结构特征与在水中的基本一致, 但波包沿C5H11/C6H12/N1H7弯曲振动+N1C6伸缩振动(υ12)和环呼吸振动(υ17)反应坐标的运动明显增强.

关键词: 共振拉曼光谱, 尿嘧啶, 动态结构, 5-氯尿嘧啶

Abstract:

We obtained resonance Raman spectra and UV absorption spectra of 5-chlorouracil and uracil in methanol and in water. B3LYP/6-311+G(d,p), B3LYP-TD/6-311+G(d,p), and CIS/6-311+G(d,p) computations were carried out to predict their ground state geometries, ground state vibrational frequencies, electronic transition energies, and 1S2 excited state geometries for 5-chlorouracil and uracil. The resonance Raman spectra of 5-chlorouracil and uracil were assigned based on our FT-Raman and FT-IR measurements and density functional theory calculations. Their absorption cross-sections and absolute resonance Raman cross-sections were quantitatively simulated using the time-dependent wave packet formalism. Excited state structural dynamics associated with the lowest singlet 1(π, π*) state was obtained. Results indicate that the major feature of the initial excited state structural dynamics of 5-chlorouracil is along the C5=C6 stretch + C6H12 bending and N3H9/N1H7 bending + N1C6 stretch reaction coordinates, while that of uracil is mostly along the ring stretch + C5H11/C6H12/N1H7 bending and C4=O10 stretch reaction coordinates. We conclude that substitution of 5-Hby a Cl atom results in a p-πconjugation interaction between the pz orbital of the Cl atom and the π or π* orbital of the pyrimidine ring. This makes the vibrational reorganizational energies more partitioned into the ring bending vibrational modes and the C5=C6 vibrational mode for 5-chlorouracil. The major feature of the initial excited state structural dynamics of uracil in methanol is similar to that in water and the wave-packet motions along the C5H11/C6H12/N1H7 bending + N1C6 stretch (υ12) and the ring breathing (υ17) reaction coordinates of uracil are obviously enhanced in methanol relative to those in water.

Key words: Resonance Raman spectrum, Uracil, Dynamic structure, 5-Chlorouracil

MSC2000: 

  • O643