Matrix effects on the charge resonance energy of the dimer cations. Low-temperature radiolysis of glassy aromatic solutions
Matrix effects on the charge resonance energy of the dimer cations. Low-temperature radiolysis of glassy aromatic solutions
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基质对二聚体阳离子电荷共振能量的影响。
DOI：
10.1021/j100587a006
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发表时间：
1975
期刊：
影响因子：
--
通讯作者：
W. Funk
中科院分区：
文献类型：
--
作者：
R. E. Buehler;W. Funk
将辐照后的有机玻璃中几种芳香族化合物的近红外吸收带归属于相应二聚体阳离子的电荷共振带。观察到的这些带随基质特征的剧烈变化与二聚体阳离子结构的变化相对应：硬基质(如甲基环己烷)强烈扭曲了二聚体阳离子，从而降低了电荷共振能量，除非涉及空间效应(苯和叔丁基苯之间的差异)。在软化基质时，有一个连续的弛豫过程，同时电荷共振能增加，直到达到自由二聚体阳离子的构象。结果表明，苯和叔丁基苯形成了相当疏松的络合物，具有较大的基质效应，而萘二聚体阳离子是非常紧密的络合物，没有基质效应，溴苯是中间体。在这种基质效应的背景下，重新考虑了Ekstrom早先发表的含苯体系的谱带分配。对于含有苯和CCl$sub3$Br的3MP玻璃，苯二聚体阳离子在740 nm处吸收，在740 nm处等温衰变为新的瞬变峰。吸收的相应变化不可能与基质效应有关。新的740-nmmore谱带暂时归属于苯阳离子与CCl$sub3$Br之间的络合物。溴苯二聚体阳离子在3MP中的衰变导致在570 nm处形成新的吸收峰。这被分配给(BrBrPh)电荷转移络合物。(Auth)(更少)
Near-infrared absorption bands due to several aromatic hydrocarbons in irradiated organic glasses were assigned to the charge resonance band of the corresponding dimer cations. The observed drastic changes of these bands with the matrix characteristics were found to correspond to the changes in the structure of the dimer cation: a hard matrix (e.g., methylcyclohexane) strongly distorts the dimer cation, thereby reducing the charge resonance energy, unless steric effects are involved (difference between benzene and tert-butylbenzene). On softening the matrix there is a continuous relaxation process with a simultaneous increase in the charge resonance energy, until the conformation of the free dimer cation is reached. It is concluded that benzene and tert- butylbenzene do form quite loose complexes, suffering large matrix effects, that the naphthalene dimer cation is a very tight complex with no matrix effects, and that bromobenzene is intermediate. Earlier published band assignments by Ekstrom for systems with benzene are reconsidered in the context of this matrix effects. For a 3MP glass with benzene and CCl$sub 3$Br the benzene dimer cation decays isothermally (77$sup 0$K) into a new transient, absorbing at 740 nm. The corresponding changes in the absorptions cannot be related to a matrix effect. The new 740-nmmore » band was tentatively assigned to a complex between the benzene cation and CCl$sub 3$Br. The decay of the bromobenzene dimer cation in 3MP leads to the formation of a new absorption at 570 nm. This is assigned to the (Br- BrPh) charge transfer complex. (auth)« less