Topological effects on intramolecular electron transfer via quantum interference
Topological effects on intramolecular electron transfer via quantum interference
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DOI：
10.1021/ic970013m
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发表时间：
1997-10-22
影响因子：
4.6
通讯作者：
Gourdon, A
中科院分区：
文献类型：
--
作者：
Patoux, C;Coudret, C;Gourdon, A
制备了二茂铁苯的三个同分异构体（邻位，10；间位，1m；对位，1p）和间二茂铁苯的5取代衍生物，R = NH2(2)、Cl(3)、CH3(4)、CN(5)、NO2(6)和N(CH3)(3)(3+)(7)。10、3和5的晶体结构已经被解出。在3和5中，环戊二烯环几乎平行于苯平均面，其夹角在9.99 ~ 14.74°之间。一个二茂铁基团在平均分子平面上，另一个在平均分子平面下。例如，苯和环戊二烯环之间有一个重要的扭曲(68.6（8)度和32.5(8)度），这是由于空间的原因。控制电位电解产生混合价二茂铁/二茂铁与同价物种的比例平衡。已观察到价间跃迁，并从比例法进行了修正。从价间带参数出发，利用Hush方程计算了金属-金属耦合（V-ab）。10 （0.025 eV）和1p （0.043 eV）的值远高于1m （0.012 eV）的值，而取代的间二茂铁苯2-6的变化很小或没有变化。这些结果被扩展的哈克分子轨道计算合理化。Im中相互作用的弱点最终可以追溯到量子干涉效应，即两个电子转移路径的贡献抵消。这种抵消的发生是因为每条路径都意味着金属轨道与不同的配体轨道的混合，并且产生的分子轨道表现出不同的对称性。
The three isomers of diferrocenylbenzenes (ortho, 1o; meta, 1m; para, 1p) as well as 5-substituted derivatives of m-diferroceylbenzene with R = NH2 (2), Cl (3), CH3 (4), CN (5), NO2 (6), and N(CH3)(3)(3+) (7) have been prepared. Crystal structures of 10, 3, and 5 have been solved. In 3 and 5, the cyclopentadienyl rings are nearly parallel to the benzene mean planes with angles ranging from 9.99(5)degrees to 14.74(5)degrees. One ferrocene group is above and the other below the mean molecular plane. For lo, there is an important twist between the benzene and cyclopentadiene rings (68.6(8)degrees and 32.5(8)degrees) for steric reasons. Controlled potential electrolysis yields the mixed-valence ferrocene/ ferrocenium species in comproportionation equilibrium with homovalent species. Intervalence transitions have been observed and corrected from comproportionation. From the intervalence band parameters, metal-metal couplings (V-ab) are calculated using Hush's equation. The values are much higher for 1o (0.025 eV) and 1p (0.043 eV) than for 1m (0.012 eV) and exhibit little or no variation for the substituted m-diferrocenylbenzenes 2-6. These results are rationalized by extended Huckel molecular orbital calculations. The weakness of the interaction in Im can be ultimately traced to a quantum Interference effect, i.e., a cancellation of the contributions of two electron transfer paths. This cancellation occurs because each path implies a mixing of metal orbitals with a different ligand orbital, and the resulting molecular orbitals exhibit different symmetries.