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Theoretical Investigations of 4-dimethylaminobenzonitrile (DMABN): Dual fluorescence and Resonance Raman spectras
LIU Li-Qian, LIANG Wan-Zhen *
College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005
*Correspondence author
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Funding: The Ph.D. Programs Foundation of Ministry of Education of China(No.20120121110010)
Opened online:31 May 2016
Accepted by: none
Citation: LIU Li-Qian, LIANG Wan-Zhen.Theoretical Investigations of 4-dimethylaminobenzonitrile (DMABN): Dual fluorescence and Resonance Raman spectras[OL]. [31 May 2016] http://en.paper.edu.cn/en_releasepaper/content/4694655
 
 
4-dimethylaminobenzonitrile (DMABN) has been intensively studied due to its solvent-dependent dual fluorescence and nonlinear optical properties. This work presents a systematically theoretical investigations on the electronic structure property, dual fluorescence mechanism and NRS and RRS spectra in gas phase and methanol solvent. The density functional theory or time-dependent DFT (TDDFT) coupled with polarizable continuum model (PCM) is adopted to describe the molecule in methanol solution. It is concluded that the solvent and hydrogen bond effects reduce the energy gap of locally excited (LE) and charge transfer (CT) states; The fluorescence mechanism of DMABN in gas phase and methanol solvent is different in gas phase, the single normal fluorescence is chiefly emitted from the LE state through the internal conversion from CT to LE state. In methanol solvent, the normal fluorescence may be emitted from the LE state and the redshifted fluorescence comes from the CT state. It is confirmed that the intramolecular charge transfer (ICT) reaction from the LE state to CT state leads to the dual fluorescence in polar solvent. To further validate our conclusion, NRS and RRS calculated with the vertical gradient (VG) approximation which nicely yields the positions and relative magnitude order of band intensities compared with the experiment. With the inclusion of the strong vibration coupling of the LE and CT states, and the Herzberg-Teller (HT) vibronic coupling effect, the calculated spectra agree well with the experimental spectra..
Keywords:Electronic structure; Hydrogen bond; Dual fluorescence; Resonance Raman spectra(RRS)
 
 
 

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