Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (01): 17-24.doi: 10.3866/PKU.WHXB20110132

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

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).

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