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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ab Initio EOM-CCSD Investigation of One-Bond C-C, N-C, and N-N Spin-Spin Coupling Constants in Fluoroazines
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Ab Initio EOM-CCSD Investigation of One-Bond C-C, N-C, and N-N Spin-Spin Coupling Constants in Fluoroazines

机译：氟嗪类单键C-C，N-C和N-N自旋耦合常数的从头算EOM-CCSD研究

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Ab initio EOM-CCSD calculations were carried out to examine one-bond 1J (C-C), 1J(N-C), and 1J(N-N) spin-spin coupling constants in benzene, pyridine, the diazines, and selected triazines, tetrazines, and pentazine and their fluoro-substituted derivatives. Relative to benzene, 1J(C-C) decreases in the azines as N atoms are introduced into the ring, but this decrease does not exceed 5 Hz. In the fluoro-substituted derivatives, 1J(C-C) may increase only slightly if the coupled carbon atoms form C-H bonds, or increase dramatically if either or both of the coupled atoms participate in C-F bonds. The value of 1J(C-C) also depends on the nature of the bonding of the coupled atoms in the ring. The largest increase is found when both carbons participate in C-F bonds, and both are ortho to N atoms. Relative to pyridine, 1J(N-C) increases as N atoms are introduced into the ring, with the magnitude of the increase depending on the bonding of the coupled atoms. It is negligible if neither atom is bonded to another N, increases if one of the coupled atoms is bonded to another N atom, and increases further if both are bonded to other N atoms. Fluoro-substitution has an opposing effect on 1J(N-C), making this coupling constant less positive or negative when the coupled C participates in a C-F bond. The decrease in 1J(N-C) relative to the parent molecule is enhanced if either of the coupled atoms is bonded to another N atom or to another C-F group. A further enhancement occurs if both coupled atoms are so bonded, with the largest increases associated with the bonding scheme in which the coupled C is bonded to another N and the coupled N to another C-F. Fluoro-substitution has a small effect on 1J(N-C) if the coupled C forms a C-H bond, and on 1J(N-N). Thus, the effects of fluoro-substitution on one-bond couplings tend to be localized.
机译：从头开始进行EOM-CCSD计算以检查苯，吡啶，二嗪和选定的三嗪，四嗪和戊嗪中的一键1J（CC），1J（NC）和1J（NN）自旋-自旋耦合常数及其氟取代的衍生物。相对于苯，随着N原子被引入环中，嗪中的1J（C-C）降低，但该降低不超过5 Hz。在氟取代的衍生物中，如果偶合的碳原子形成C-H键，则1J（C-C）可能仅略有增加，或者如果其中一个或两个偶合的原子参与C-F键，则1J（C-C）可能会急剧增加。 1J（C-C）的值还取决于环中耦合原子的键合性质。当两个碳都参与C-F键且都与N原子相邻时，发现最大的增加。相对于吡啶，随着N原子被引入环中，1J（N-C）增加，其增加幅度取决于耦合原子的键合。如果两个原子都没有键合至另一个N，如果一个耦合原子中的一个键合至另一个N原子，则增加，而如果两个原子均与其他N原子键合，则进一步增加，则可以忽略不计。氟取代对1J（N-C）具有相反的作用，当偶合的C参与C-F键时，该偶合常数的正或负变小。如果任何一个耦合原子与另一个N原子或另一个C-F基团键合，则相对于母体分子的1J（N-C）降低会增强。如果两个偶合的原子都这样键合，则会进一步增强，这与键合方案相关的最大增加，在键合方案中，偶合的C与另一个N键合，而偶合的N与另一个C-F键合。如果偶联的C形成C-H键，则氟取代对1J（N-C）的影响较小，对1J（N-N）的影响较小。因此，氟取代对单键耦合的影响倾向于局部化。

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