Femtosecond time-resolved absorption anisotropy spectroscopy on 9,9'-bianthryl: detection of partial intramolecular charge transfer in polar and nonpolar solvents.
Femtosecond time-resolved absorption anisotropy spectroscopy on 9,9'-bianthryl: detection of partial intramolecular charge transfer in polar and nonpolar solvents.
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DOI：
10.1063/1.3043368
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发表时间：
2009-01
期刊：
影响因子：
--
通讯作者：
T. Takaya;H. Hamaguchi;K. Iwata
中科院分区：
文献类型：
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作者：
T. Takaya;H. Hamaguchi;K. Iwata
发展了多道探测飞秒时间分辨吸收各向异性光谱。用这种方法揭示了紫外光激发的9，9(‘)-联苯并[BA]在庚烷、乙腈和乙醇中的电荷转移(CT)特性和动力学。利用吸收各向异性谱将瞬时吸收谱分解为两个各向异性值不同的吸收分量。分解结果表明，两个吸收带具有不同的各向异性值或不同的跃迁偶极矩方向。其中一个跃迁偶极子垂直于中心C-C键的谱带，其光谱形状与单重态激发态中菲的瞬时吸收几乎相同。这个带被指定为局部激发的蒽环中的一个跃迁。另一个频段很宽，没有结构。这个带被认为是部分电荷转移(PCT)吸收，因为它的跃迁偶极矩平行于中心C-C键。因为PCT带在非极性溶剂庚烷和极性溶剂中都能观察到，所以PCT既存在于非极性溶剂中，也存在于极性溶剂中。PCT波段在仪器响应范围内上升，表明PCT在光激发后立即发生。在乙腈中，CT组分表现出明显的蓝移，表明从PCT状态形成了稳定的CT状态。在乙醇中，CT谱带没有显示光谱位移，这表明稳定性比在乙腈中要小。根据这些结果，讨论了BA分子内CT的新的动力学模型。
Femtosecond time-resolved absorption anisotropy spectroscopy by multichannel detection has been developed. The charge transfer (CT) character and dynamics of the UV-photoexcited 9,9(')-bianthryl (BA) in heptane, acetonitrile, and ethanol are revealed with this method. The transient absorption spectra are decomposed into two absorption components with different anisotropy values by the absorption anisotropy spectra. The decomposition results show two absorption bands having different anisotropy values or different directions of the transition dipole moment. One band that has the transition dipole perpendicular to the central C-C bond has almost an identical spectral shape with transient absorption of anthracene in the singlet excited state. This band is assigned to a transition in a locally excited anthracene ring. The other band is broad and structureless. This band is assigned to partial charge transfer (PCT) absorption because its transition dipole moment is parallel to the central C-C bond. Because the PCT band is observed in a nonpolar solvent heptane as well as in polar solvents, the PCT occurs in both nonpolar and polar solvents. The PCT band rises within the instrumental response, indicating that the PCT takes place immediately after the photoexcitation. In acetonitrile, the CT component shows a significant blueshift, indicating the formation of the stabilized CT state from the PCT state. In ethanol, the CT band does not show a spectral shift, suggesting that the stabilization is smaller than in acetonitrile. From these results, a new kinetic model on the intramolecular CT in BA is discussed.