Nuclear Spin-Spin Coupling via Nonbonded Interactions. 8.1 The Distance Dependence of Through-Space Fluorine-Fluorine Coupling

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• 作者：Frank B. Mallory ; Clelia W. Mallory ; Kelly E. Butler ; Mary Beth Lewis ; Angell Qian Xia ; Eddie D. Luzik ; Jr. ; Laura E. Fredenburgh ; Mercy M. Ramanjulu ; Que N. Van ; Michelle M. Francl ; Dana A. Freed ; Ch
• 刊名：Journal of the American Chemical Society
• 出版年：2000
• 出版时间：May 3, 2000
• 年：2000
• 卷：122
• 期：17
• 页码：4108 - 4116
• 全文大小：215K
• 年卷期：v.122,no.17(May 3, 2000)
• ISSN：1520-5126

文摘

The ¹⁹F¹⁹F nuclear spin-spin coupling constants J_FF for a set of eighteen compounds relatedstructurally to 1,8-difluoronaphthalene were measured by ¹⁹F NMR spectroscopy. The FF distances d_FF inthese compounds were determined by ab initio 3-21G* molecular orbital calculations. Consistent with thelone-pair overlap theory of the origins of through-space ¹⁹F¹⁹F coupling, an exponential relationship is foundbetween J_FF and d_FF (regression coefficient r² = 0.991), and a linear relationship is found between J_FF and theextent of the overlap interaction between the in-plane fluorine 2p lone-pair orbitals (regression coefficient r²= 0.993). The magnitudes of these lone-pair interactions were estimated from molecular orbital energies obtainedby ab initio 6-31G* calculations for a model consisting of a pair of HF molecules separated by various distances.