Excited state relaxation paths in 9,9′-bianthryl and 9-carbazolyl-anthracene:: a sub-ps transient absorption study
Excited state relaxation paths in 9,9′-bianthryl and 9-carbazolyl-anthracene:: a sub-ps transient absorption study
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DOI：
10.1016/s0301-0104(99)00386-9
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发表时间：
2000-03-01
期刊：
影响因子：
2.3
通讯作者：
Rettig, W
中科院分区：
文献类型：
--
作者：
Jurczok, M;Plaza, P;Rettig, W
据报道，乙醇、正丁醇和乙醚中的 9,9'-联蒽 (BA) 和 9-咔唑基蒽 (C9A) 在 320 至 800 nm 范围内具有亚皮秒分辨率的瞬时吸收光谱。在紫外区域可以看到基态漂白和激发态吸收 (ESA)。在醇中，ESA 衰减（乙醇中约为 20 ps，丁醇中约为 70 ps）与可见光中众所周知的电荷转移 (CT) 带的上升时间相匹配，时间常数与平均溶剂化时间相当。在荧光区域（400-480 nm）观察到 BA 的额外变化，其特征是结构化增益贡献在不到 1 ps 内消失。在乙醚中也观察到了这一点，尽管随后的演变有所不同。这种超快过程归因于 BA 在 Franck-Condon 几何结构中不受阻碍的扭转松弛，但对于 C9A 来说不太清楚。然而，对于醇中的两种化合物来说，CT 态的形成是第二步，并且速度要慢一个数量级以上。在二乙醚中，引发不受阻碍且扩散的构象变化。数据支持 BA 的双坐标（内部扭转和溶剂运动）弛豫模型，这些坐标的相对重要性强烈依赖于溶剂。为 C9A 提出了类似的模型。 (C) 2000 Elsevier Science B.V. 保留所有权利。
Transient absorption sprectra with sub-picosecond resolution are reported for 9,9'-bianthryl (BA) and 9-carbazolylanthracene (C9A) in ethanol, n-butanol and diethylether, from 320 to 800 nm. Ground-state bleaching and excited-state absorption (ESA) are seen in the UV region. In alcohols, the ESA decay (approximate to 20 ps in ethanol and approximate to 70 ps in butanol) matches the rise time of the well-known charge-transfer (CT) band in the visible, with a time constant comparable to the average solvation time. An additional change is observed for BA in the fluorescence region (400-480 nm), characterized by the disappearance of a structured gain contribution in less than 1 ps. This is also observed in diethylether, although the subsequent evolution is different. This ultrafast process, which is attributed to the unhindered torsional relaxation of BA out of the Franck-Condon geometry, is less clear for C9A. However, for both compounds in alcohols, the CT state formation is a second step and is more than one order of magnitude slower. In diethylether, unhindered and diffusive conformational changes are invoked. The data support a two-coordinate (internal twisting and solvent motion) relaxation model for BA, the relative importance of these coordinates being strongly solvent dependent. A similar model is proposed for C9A. (C) 2000 Elsevier Science B.V. All rights reserved.