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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photophysical properties of intramolecular charge transfer in two newly synthesized tribranched donor-π-acceptor chromophores
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Photophysical properties of intramolecular charge transfer in two newly synthesized tribranched donor-π-acceptor chromophores

机译：两个新合成的三支供体-π-受体生色团的分子内电荷转移的光物理性质

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The nature of optical excitation and the degree of intramolecular charge transfer (ICT) as well as the dynamics of excited ICT states of two new tribranched donor-π-acceptor molecules with acceptor-terminated (DA _3) and acceptor-centered (AD_3) geometries have been investigated by steady-state and femtosecond time-resolved stimulated emission fluorescence depletion (FS TR-SEP FD) measurements in different polar solvents. The interpretation of the experimental results is based on the comparative investigation of the two D-π-A compounds with respect to the model monomer counterpart (DA). The larger solvatochromic effects and stronger solvent dependence of spectral properties of DA_3 than that of AD_3 indicate that the excited ICT state of DA_3 possesses higher polarity and larger dipole moments compared to those of AD_3. The similarity of absorption and strong solvent-dependent fluorescence spectra of DA_3 and DA reveals that the excited-state properties of DA_3 are identical to that of the model DA, which localized on one of the branches in DA _3. In contrast to DA_3, the large red shift in the absorption and the small Stokes shift of AD_3 suggest the formation of a delocalized ICT state to a certain extent in the excited state of AD _3. The dynamic behavior of excited ICT states for all three compounds are also investigated by femtosecond time-resolved stimulated emission depletion (FS TR-SEP FD) measurements, where the excited-state relaxations are highly dependent on both solvent polarity and the polar degree of the excited ICT states. Furthermore, the steady-state fluorescence excitation anisotropy shows that the intramolecular excitation transfer among the three disorder-induced localized ICT states with nondegenerate transition dipole moments is involved within DA_3. Compared to DA_3, a substantial red shift in the absorption of AD_3 results from the formation of a delocalized ICT state, where the specific excitation anisotropy spectrum shows that the excitation energy is mainly redistributed between the localized ICT state and the delocalized ICT state.
机译：两种新的具有支化端基（DA _3）和以受体中心（AD_3）几何结构的三支供体-π-受体分子的光激发性质和分子内电荷转移（ICT）的程度以及激发的ICT状态的动力学已经通过在不同极性溶剂中的稳态和飞秒时间分辨的受激发射荧光耗竭（FS TR-SEP FD）测量进行了研究。实验结果的解释是基于两种D-π-A化合物相对于模型单体对应物（DA）的比较研究。与AD_3相比，DA_3的溶剂变色效应更大，光谱特性对溶剂的依赖性更强，表明DA_3的激发ICT状态具有更高的极性和更大的偶极矩。 DA_3和DA的吸收光谱和强溶剂依赖性荧光光谱相似，表明DA_3的激发态性质与模型DA的激发态性质相同，后者位于DA _3中的一个分支上。与DA_3相比，AD_3的吸收中的大红移和Stokes位移小，表明在AD _3的激发态中一定程度上形成了离域ICT状态。还通过飞秒时间分辨的受激发射耗竭（FS TR-SEP FD）测量研究了所有三种化合物的ICT激发态的动态行为，其中激发态弛豫高度依赖于溶剂的极性和极性的极性。激动的ICT状态。此外，稳态荧光激发各向异性表明，DA_3参与了具有无简并跃迁偶极矩的三种无序诱导的局部ICT状态之间的分子内激发转移。与DA_3相比，AD_3吸收的吸收发生了大幅度的红移，这是由于离域ICT状态的形成所致，其中特定的激发各向异性谱表明，激发能主要在局部ICT状态和离域ICT状态之间重新分配。

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