摘要
利用稳态和瞬态光谱以及量化计算的方法对基于三并咔唑(TAT)的八极分子(DA_3)的光物理性质进行了系统的研究。研究结果证明了这一体系具有明显的电荷转移特性:三并咔唑作为一个平面化的强电子给体,连接不同的电子受体所形成的八极分子发生了从富电子的中心基团到缺电子的周围基团的分子内电荷转移,这一光致分子内电荷转移特性令这一类分子体系表现出良好的双光子吸收性质,其双光子吸收正比于跃迁偶极矩(M_(ge))以及激发态与基态的偶极矩差值(△_μge))的平方。在不同极性的溶剂中的稳态荧光峰位置随着溶剂极性增加有很明显的红移,表明激发态分子具有偶极性性质。溶剂化和激发态动力学的结果表明该分子体系的激发态趋向于形成定域在其中一个偶极分支上,这有利于获得更大的M_(ge)和△μ_(ge),因此导致双光子吸收的增强。
The photophysical properties of three octupolar chromophores containing planar triazatruxene(TAT) as the central electron donor with different electron-withdrawing groups in the tribranched arrangement have been systematically investigated by means of steady-state and transient spectroscopy.The multidimensioned intramolecular charge transfer(ICT) properties of these tribranched chromophores related to the observed two-photon absorption(TPA)properties are explored by estimating the TPA essential factors(M_(ge) and Δμ_(ge)).Besides the large Stokes shift between steady state absorption and fluorescence spectra in different polar solvents,photoinduced ICT was further demonstrated by quantum-chemical calculations and transient absorption measurements.Both quantum calculations and spectral experiments show that a multidimensional ICT occurs from electron-rich core to the electron-deficient periphery of these TAT derivatives.The results of solvation effects and the dynamics of the excited states show that the excited states of these three chromophores tend to exhibit an excitation localization on one of the dipolar branches,which is beneficial to achieve large M_(ge) and Δμ_(ge),thus leading to enhanced TPA properties.
引文
[1]He,G.;Shao,J.;Li,Y.;Hu,J.;Zhu,H.;Wang,X.;Guo,Q.;Chi,C.;Xia,A.,Phys.Chem.Chem.Phys.2016,18(9),6789-6798.
[2]Shao,J.;Guan,Z.;Yan,Y.;Jiao,C.;Xu,Q.-H.;Chi,C.,J.Org.Chem.2011,76(3),780-790.