物理化学学报 >> 2011, Vol. 27 >> Issue (01): 17-24.doi: 10.3866/PKU.WHXB20110132

热力学,动力学和结构化学 上一篇    下一篇

6-N,N-二甲基腺嘌呤激发态结构动力学的共振拉曼光谱

刘崇, 杜蕊, 赵彦英, 王惠钢, 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, 生态染整技术教育部工程研究中心, 杭州310018
  • 收稿日期:2010-08-13 修回日期:2010-10-13 发布日期:2010-12-31
  • 通讯作者: 郑旭明 E-mail:zxm@zstu.edu.cn
  • 基金资助:

    国家重点基础研究发展规划(973) (2007CB815203), 国家自然科学基金(21033002, 20573097)和浙江省自然科学基金(R405465)资助项目

Resonance Raman Spectroscopy of the Excited State Structural Dynamics of 6-N,N-Dimethyladenine

LIU Chong, DU Rui, ZHAO Yan-Ying, WANG Hui-Gang, ZHENG Xu-Ming   

  1. Key Laboratory of Advanced Textiles Materials and Manufacture Technology, and Engineering Research Center for Eco-dyeing and Finishing of Textiles, Ministry of Education, Department of Chemistry, Zhejiang Science and Technology University, Hangzhou 310018, P. R. China
  • Received:2010-08-13 Revised:2010-10-13 Published:2010-12-31
  • Contact: ZHENG Xu-Ming E-mail:zxm@zstu.edu.cn
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (973) (2007CB815203), National Natural Science Foundation of China (21033002, 20573097), and Natural Science Foundation of Zhejiang Province, China (R405465).

摘要:

采用共振拉曼光谱技术和密度泛函理论方法研究了6-N,N-二甲基腺嘌呤(DMA)的A带和B带电子激发和Franck-Condon 区域结构动力学. πHπL*跃迁是A带吸收的主体, 其振子强度约占整个A带吸收的79%.由弥散轨道参与的n→Ryd 和πH→Ryd 跃迁在B带跃迁中扮演重要角色, 其振子强度约占B带吸收的62%,而在A带吸收中占主导的πHπL*跃迁的振子强度在B带吸收中仅占33%. 嘌呤环变形伸缩+C8H/N9H面内弯曲振动ν23和五元环变形伸缩+C8H弯曲振动ν13的基频、泛频和合频占据了A带共振拉曼光谱强度的绝大部分, 说明1πHπL*激发态结构动力学主要沿嘌呤环的变形伸缩振动, N9H/C8H/C2H弯曲振动等反应坐标展开, 而ν10, ν29, ν21, ν26ν40的基频、泛频和合频占据了B带共振拉曼光谱强度的主体部分, 它们决定了B带激发态的结构动力学. A带共振拉曼光谱中ν26ν12被认为与1nπ*/1ππ*势能面锥型交叉有关. B带共振拉曼光谱中ν21的激活与1ππ*/1πσN9H*势能面锥型交叉相关.

关键词: 6-N,N-二甲基腺嘌呤, 激发态结构动力学, 共振拉曼光谱, 电子激发

Abstract:

The A- and B-band electronic excitations and the excited state structural dynamics of 6-N,N-dimethyladenine (DMA) were studied by resonance Raman spectroscopy and density functional theory calculations. The πHπL* transition is the main part of the A-band absorption and its calculated oscillator strength occupies 79% of the A-band absorption. n→Ryd and πH→Ryd transitions where Ryd denotes the diffuse Rydberg orbital play important roles in the B-band electronic transitions and their calculated oscillator strengths occupy about 62% of the B-band absorption. The oscillator strength for the πHπL* transition, which dominates the A-band electronic transition only occupies about 33% of the B-band absorption. The foundamental vibrations of the purine ring deformation stretch plus the C8H/N9H bend mode ν23 and the 5 member ring deformation stretch plus the C8H bend mode ν13, and their overtones and combination bands occupy most of the A-band resonance Raman intensities. Therefore, the 1πHπL* excited state structural dynamics of DMA is mainly along the ν23 and ν13 reaction coordinates. The majority of the B-band resonance Raman intensities are dominated by the fundamental vibrations of ν10, ν29, ν21, ν26, ν40, and their overtones and combination bands. This suggests the B-band excited state structural dynamics of DMA is mostly along the purine ring deformation, the C6N10 stretch, the N9H/C8H/C2H bend and the N(CH3)2 antisymmetric stretch. The appearance of ν26 and ν12 in the A-band resonance Raman spectrum is correlated to the Franck-Condon region 1*/1ππ* conical intersection. The activation of ν21 in the B-band resonance Raman spectrum is correlated to the Franck-Condon region 1ππ*/1πσN9H* conical intersection.

Key words: 6-N,N-dimethyladenine, Excited state structural dynamics, Resonance Raman spectrum, Electronic transition

MSC2000: 

  • O643