Structure of dimeric radical cations of benzene and toluene in halocarbon matrices: an EPR, ENDOR and MO study
Structure of dimeric radical cations of benzene and toluene in halocarbon matrices: an EPR, ENDOR and MO study
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卤代烃基质中苯和甲苯二聚自由基阳离子的结构：EPR、ENDOR 和 MO 研究
DOI：
10.1039/b001174f
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发表时间：
2000
影响因子：
3.3
通讯作者：
A. Lund
中科院分区：
文献类型：
--
作者：
Yoshiteru Itagaki;N. Benetis;R. Kadam;A. Lund
这个
含苯和甲苯的X-射线辐照卤代烃基质中形成的二聚阳离子的结构
考察了较高浓度的溶质。EPR和Endor(电子核双核
观察到了这些二聚体阳离子的共振谱，得到了准确的HF偶合常数
得到了。苯的二聚自由基阳离子(C6H6)2+的Endor谱表现为HF偶联
由于12个当量的质子和各向同性耦合(AISO)几乎是它的一半
在单体阳离子中。在CFCl3矩阵中观察到具有菱形对称性的Endor相变，而
在CF3CCl_3中，即使在50K下也能得到清晰的轴对称相变|A‖|<；|A⊥|。
用偶极耦合张量作为参数来估计两个配对环之间的距离。AS
对于甲苯二聚体阳离子(CH3C6H5)2+，观察到CH3和H(4，4‘)质子的Endor跃迁。
CH3质子的各向同性高频耦合更强烈地偏离半值，相当接近
到单体价值的三分之一。H(4，4‘)质子的高频耦合几乎是耦合的一半
对单体的影响。结果表明，CH3质子的反常高频耦合是由相互作用引起的
在两个环之间通过σ键。采用密度泛函理论(DFT)计算
得到了优化的几何构型和高频耦合张量，并提出了两种二聚体的三明治结构。此外，两环之间的距离和
反常CH3质子
高频耦合在光纤中的应用
成功地评价了(CH3C6H5)2+。
The
structure of dimeric cations of benzene and toluene formed in X-irradiated halocarbon matrices containing
relatively high concentration of the solutes was investigated. EPR and ENDOR (electron nuclear double
resonance) spectra of these dimer cations were observed and accurate values of the hf coupling constants
were obtained. The ENDOR spectrum of the dimeric radical cation of benzene, (C6H6)2+, exhibited hf couplings
due to twelve equivalent protons and the isotropic coupling (aiso) was almost one-half of that
in the monomer cation. ENDOR transitions with a rhombic symmetry were observed in a CFCl3 matrix, whereas
clear axially symmetric transitions with ∣A‖∣<∣A⊥∣ were obtained in CF3CCl3 even at 50 K. The rhombic
dipolar coupling tensor was used as a parameter to evaluate the distance between the two partner rings. As
regards the toluene dimer cation, (CH3C6H5)2+, ENDOR transitions of the CH3 and H(4,4′) protons were observed.
The isotropic hf coupling of the CH3 protons deviated even more strongly from the half value, being rather close
to one-third of the value of the monomer. The hf coupling of the H(4,4′) protons was almost half the coupling
of the monomer. It was suggested that the anomalous hf couplings of the CH3 protons were due to the interaction
between the two rings through the σ-bond. Density functional theory (DFT) calculations were employed
to obtain the optimized geometries and hf coupling tensors and suggested sandwich structures in both dimers. Furthermore, the distances between the two rings and the
anomalous CH3 protons
hf coupling in the
(CH3C6H5)2+ were successfully evaluated.