Applications of photoelectron spectroscopy. X. Relative importance of through-space vs. through-bond interaction between the lone pairs in 1,4-diazabicyclo[2.2.2]octane
Applications of photoelectron spectroscopy. X. Relative importance of through-space vs. through-bond interaction between the lone pairs in 1,4-diazabicyclo[2.2.2]octane
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光电子能谱的应用。
DOI：
10.1021/ja00715a064
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发表时间：
1970
影响因子：
15
通讯作者：
K. Muszkat
中科院分区：
文献类型：
--
作者：
E. Heilbronner;K. Muszkat
II，-Fe-1 - 2与能量较低的CC和/或CH轨道相互作用，产生高于a2”（n-）的序列a1“（n+）。理论预测，对于h= k= l= l，效应1占主导地位（参见结构I），<?.,对于短的N·· N距离，而（2）应该负责h，k和l都大于1的分子中孤对轨道的排序。(This图1总结了这种情况。）在本系列的前一篇文章中，我们已经证明了1，4-二氮杂双环[2.2]的光电子能谱（PE谱）中n电离带之间的分裂。2]辛烷（dabco，II）为2.13 eV，与从扩展的Hiickel模型获得的预测值1.57 eV 3合理一致。[5]然而，我们没有解决轨道a1“（n+）和a2”（n-）的排序问题。在这篇文章中，我们希望表明，对II的PE谱中两个n带的振动模式的分析强烈支持Hoffmann，Im-amura和Hehre的预测; 3即，在II的情况下，通过键的相互作用支配孤对m和n2的通过空间的相互作用。(The Dewar，6最近使用MINDO/2方法获得了相同的结果。7)图2显示了II的PE光谱中的前两个谱带（最大值在7.52和9.65 eV），这与电离过程有关，在该过程中，电子离开这些分子轨道中的一个或另一个，其中n+或n_是主要贡献者。两个谱带（图2中标记为1和2）都显示了振动精细结构，其最大值已编号
II,—fe—;—2 interaction with the energetically low-lying CC and/or CH orbitals which yields the sequence ai'(n+) above a2"(n_). Theory predicts that effect 1 dom-inates for h= k= l= 1 (see structure I),/.<?., for short N·· N distances, while (2) should be responsible for the ordering of the lone-pair orbitals in molecules in which h, k, and l are all larger than 1.(This situa-tion is summarized in Figure 1.) In a previous communication4 of this series we have shown that the splitting between the n ionization bands in the photoelectron spectrum (PE spectrum) of 1, 4-diazabicyclo [2.2. 2] octane (dabco, II) amounts to 2.13 eV, in reasonable agreement with the predicted value of 1.57 eV3 obtained from an extended Hiickel model. 5 However, we left open the question of the ordering of the orbitals ai'(n+) and a2"(n_). In this note we wish to show that an analysis of the vibrational pattern of the two n bands in the PE spectrum of II strongly supports the prediction by Hoffmann, Im-amura, and Hehre; 3 namely, that inthe case of II, the through-bond interaction dominates the through-space interaction of the lone pairs m and n2.(The same result has recently been obtained by Dewar, 6 using the MINDO/2 method. 7) Figure 2 shows the first two bands in the PE spectrum of II (maxima at 7.52 and 9.65 eV), which are associated with ionization processes in which an electron vacates one or the other of those molecular orbitals, to which n+ or n_ is the major contributor. Both bands (labeled 1 and 2 in Figure 2) show vibrational fine structure, the maxima of which havebeen numbered