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Structural Dynamics of 3-Dimethylamino-2-methyl-propenal in S2(ππ*)State (cited: 3)
Sheng Pan1, Jia-Dan Xue2, Xu-ming Zheng*1,2,3
1.Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China;2.Key Laboratory of Advanced Textiles Materials and Manufacture Technology of the Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, China;3.Engineering Research
Abstract:
The photophysics of 3-dimethylamino-2-methyl-propenal (DMAMP) after excitation to the S2(ππ*) electronic state was studied using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The transition barriers of the ground state tautomerization reactions between DMAMP and its three isomers were determined at B3LYP/6-311++G(d,p) level of theory. The vibrational spectra were assigned. The A-band resonance Raman spectra were obtained in acetonitrile with excitation wavelengths in resonance with the first intense absorption band to probe the structural dynamics of DMAMP. The B3LYP-TD computation was carried out to determine the relative A-band resonance Raman intensities of the fundamental modes, and the result indicated that the vibronic-coupling existed in Franck-Condon region. Complete active space self-consistent field (CASSCF) calculations were carried out to determine the excitation energies of the lower-lying singlet and triplet excited states, the conical intersection points and the inter-system crossing points. The A-band short-time structural dynamics and the corresponding decay dynamics of DMAMP were obtained by analysis of the resonance Raman intensity pattern and CASSCF computations. It was found that a sudden de-conjugation between C1=O6 and C2=C3 occurred at the Franck-Condon region of the S2(ππ*) state, while the enhancement of the conjugation interaction between C3 and N(CH3)2, and between C1 and C2 evolutions shortly after the wavepacket leaves away the Franck-Condon region via the excited state charge redistribution. The de-conjugation interaction between C1=O6 and C2=C3 made the rotation of C3=N(CH3)2 group around the C2-C3 bond much easier, while the enhanced conjugation between C1 and C2, and between C3 and N(CH3)2 made the rotation around the C1-C2 bond and C3-N5 more difficult. It was revealed that the initial structural dynamics of DMAMP was predominantly towards the CI-1(S2/S0) point, while the opportunities towards either CI-2(S2/S0) or CI-3(S2/S0) point were negligible. Two decay channels of DMAMP from S2,FC(ππ*) to S0 or T1,min via various CIs and ISCs were proposed.
Key words:  Structural dynamics, Conical intersection, Excited state, Resonance Raman, CASSCF calculation
FundProject:
3-二甲氨基-2-甲基丙烯醛S2激发态结构动力学 (cited: 3)
潘胜1, 薛佳丹2, 郑旭明*1,2,3
1.浙江理工大学化学系,杭州310018;2.浙江理工大学先进纺织材料与加工技术教育部重点实验室,杭州310018;3.浙江理工大学生态染整技术教育部工程中心,杭州310018
摘要:
采用共振拉曼光谱和完全活性自洽场理论计算研究了3-二甲氨基-2-甲基丙烯醛(DMAMP)光激发到S2(ππ*)态后的光物理性能.在B3LYP/6-311++G(d,p)水平计算确定了DMAMP与其三种异构体之间的基态异构化能垒,指认了振动光谱.采用涵盖紫外强吸收带的激光波长,获得了DMAMP在环己烷、乙腈和甲醇溶剂中的A-带共振拉曼光谱,含时密度泛函方法计算确定了该光谱中基频的相对强度,发现振动-电子耦合发生在S2(ππ*)态的Franck-Condon区域.CASSCF计算方法确定低单重和三重激发态、势能面锥形交叉点和系间窜跃点的激发能.共振拉曼光谱强度模式分析和CASSCF计算获得了DMAMP的A-带短时结构动力学和其后的衰变动力学表明,C1=O6和C2=C3之间的瞬时去共轭效应发生在S2(ππ*)态的Franck-Condon区域,激发态电荷重分布机制表明,C3和二甲氨基之间以及C1和C2之间的共轭增强效应发生在波包离开Franck-Condon区域后.C1=O6和C2=C3之间的去共轭效应使得-C3=N(CH3)2沿着C2-C3键旋转更加容易,C1-C2之间以及C3和N(CH3)的共轭增强效应使得绕C1-C2和C3-N5旋转变得比较困难.这些表明DMAMP初始结构动力学沿着CI-1(S2/S0)交叉点展开,而沿CI-2(S2/S0)和CI-3(S2/S0)交叉点展开的几率可以忽略.提出了DMAMP分子受光激发从S2,FC(ππ*)经由各锥形交叉点和各系间窜跃点回到S0或T1,min的两个衰变通道.
关键词:  3-二甲氨基-2-甲基丙烯醛,激发态结构动力学,异构化能垒,共振拉曼光谱,密度泛函理论
DOI:10.1063/1674-0068/27/02/149-158
分类号: