ELECTRONIC-STRUCTURES OF EXCIPLEXES AND EXCITED CHARGE-TRANSFER COMPLEXES
ELECTRONIC-STRUCTURES OF EXCIPLEXES AND EXCITED CHARGE-TRANSFER COMPLEXES
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DOI：
10.1021/ja00097a028
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发表时间：
1994-09-07
影响因子：
15
通讯作者：
FARID, S
中科院分区：
文献类型：
--
作者：
GOULD, IR;YOUNG, RH;FARID, S
对于9，10-二氰基蒽和2，6，9，10-四氰基蒽作为电子受体与烷基苯作为电子供体形成的激基复合物和激发态电荷转移（CT）复合物，辐射速率常数（k（f））随着发射能量的增加而增加。k（f）的增加归因于发光物质的电荷转移特性的相应降低。这是解释在纯离子对和局部激发态的发射状态的相对贡献。随着溶剂极性的降低和受体/供体对（E（D）（ox）-E（A）（red））的氧化还原能量的增加，纯离子对状态的能量升高，并且与局部激发态的混合增加。k（f）对发射能量的依赖性进行了定量分析，使用三态模型，其中的第一个本地激发单重态的氰基蒽，纯离子对状态，和中性状态之间的混合被考虑在内。本文还讨论了数据分析的简化方法。从分析中，激基复合物/激发CT复合物的电子结构和发射频率之间的关系得到。对于这些受体/供体系统，当它们的发射最大能量比受体激发单重态的0，0跃迁低约10%时，发射物质可以被认为是基本上纯的接触自由基-离子对（> 90%CT特征）。5000 cm（-1）。的值。1300 - 1350 cm（-1）。相应的耦合离子对和中性态的矩阵元是ca。750 - 900 cm（-1），这与以前从密切相关物种的非辐射电子转移率研究中估计的结果相似。
For the exciplexes and excited charge-transfer (CT) complexes formed between 9,10-dicyanoanthracene and 2,6,9,10-tetracyanoanthracene as electron accepters and alkylbenzenes as donors, the radiative rate constants (k(f)) increase with increasing emission energy. The increase in k(f) is attributed to a corresponding decrease in the charge-transfer character of the emitting species. This is explained in terms of the relative contributions of pure ion-pair and locally excited states to the emitting state. With decreasing solvent polarity and with increasing redox energy of the acceptor/donor pair (E(D)(ox) - E(A)(red)), the energy of the pure ion-pair state is raised and mixing with the locally excited states increases. The dependence of k(f) on emission energy is analyzed quantitatively using a three-state model in which mixing among the first locally excited singlet state of the cyanoanthracenes, the pure ion-pair state, and the neutral state is taken into account. Simplified methods for data analysis are also discussed. From the analyses, the relationship between the electronic structures of the exciplex/excited CT complexes and the emission frequency is obtained. For these acceptor/donor systems, the emitting species can be considered to be essentially pure contact radical-ion pairs (>90% CT character) when their emission maxima are lower in energy than the 0,0 transition of the acceptor excited singlet states by ca. 5000 cm(-1). Values of ca. 1300-1350 cm(-1) are obtained for the electronic matrix elements coupling the locally excited and ion-pair states. The corresponding matrix elements for coupling the ion-pair and the neutral states are ca. 750-900 cm(-1), which are similar to those estimated previously from studies of the rates of nonradiative electron transfer in closely related species.