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Electron-donating strength dependent symmetry breaking charge transfer dynamics of quadrupolar molecules.
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2020-06-29 , DOI: 10.1039/d0cp02527e
Xinmiao Niu 1 , Zhuoran Kuang , Miquel Planells , Yuanyuan Guo , Neil Robertson , Andong Xia
Affiliation  

The excited state symmetry breaking charge transfer (SBCT) dynamics of two diacetylide-triphenylamine (DATPA) derivatives with different electron-donating abilities are investigated by femtosecond transient absorption and fluorescence spectroscopy. By tracking the evolution of the excited states by transient absorption spectra and the kinetics of the instantaneous emission dipole moments obtained from transient fluorescence spectroscopy, it is found that, in nonpolar solvent, the relaxed S1 state is quadrupolar with little change of emission dipole moments for the two molecules within 30 ps, whereas in polar solvent, the quadrupolar state evolves to a symmetry broken S1 state, in which, the emission dipole moment exhibits a fast reduction in the first few picoseconds. The larger reduction in emission transition dipole moment for the molecule with stronger electron-donating methoxy groups indicates a larger extent of symmetry breaking compared with the one with weak electron-donating methyl groups. Consequently, we revealed that the magnitude of symmetry breaking can be tuned by changing the electron-donors in quadrupolar molecules.

中文翻译:

电子给体强度依赖性对称性破坏了四极分子的电荷转移动力学。

通过飞秒瞬态吸收和荧光光谱研究了两种具有不同供电子能力的二乙炔-三苯胺(DATPA)衍生物的激发态对称断裂电荷转移(SBCT)动力学。通过利用瞬态吸收光谱跟踪瞬态荧光光谱获得的激发态的演化以及瞬态荧光光谱学获得的瞬时发射偶极矩的动力学,发现在非极性溶剂中,弛豫的S 1状态为四极,发射偶极矩的变化很小。对于30 ps内的两个分子,而在极性溶剂中,四极态演化成对称的S 1状态,其中发射偶极矩在头几皮秒内显示出快速减小。具有给电子氧基的甲氧基较强的分子的发射跃迁偶极矩减小较大,这表明与具有给电子弱的甲基的分子相比,对称性破坏程度更大。因此,我们发现可以通过改变四极分子中的电子给体来调节对称破坏的幅度。
更新日期:2020-07-15
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