Mechanochemical Production of Halogen-Bonded Solids Featuring P鈺怬路路路I鈥揅 Motifs and Characterization via X-ray Diffraction, Solid-State Multinuclear Magnetic Resonance, and Density Functional Theory

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• 作者：Yijue Xu ; Jasmine Viger-Gravel ; Ilia Korobkov ; David L. Bryce
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：December 3, 2015
• 年：2015
• 卷：119
• 期：48
• 页码：27104-27117
• 全文大小：756K
• ISSN：1932-7455

文摘

A series of phosphine oxide-iodofluorobenzene cocrystals featuring relatively strongly halogen-bonded P鈺怬路路路I鈥揅 motifs has been prepared mechanochemically and characterized by ³¹P and ¹⁷O solid-state nuclear magnetic resonance (SSNMR) spectroscopy and single-crystal X-ray diffraction. Direct insights were obtained into the correlation between several NMR observables (chemical shift tensors, electric field gradient tensors, and J(³¹P, ¹⁷O) coupling) and the molecular and electronic structure of the halogen bonds. The ³¹P isotropic chemical shift and span, the ¹⁷O quadrupolar coupling constant and asymmetry parameter, as well as J(³¹P, ¹⁷O) coupling can be strong indicators of the presence of a halogen bond. Density functional theory calculations using periodic boundary conditions have revealed several notable trends. For example, the oxygen isotropic chemical shift and J(³¹P, ¹⁷O) values were found to correlate linearly with the strength of the halogen bond. An additional natural localized molecular orbital (NLMO) investigation shows that the three main contributions to J(³¹P, ¹⁷O) coupling are the P鈺怬 bonding orbitals, the oxygen lone pair orbital, and oxygen core orbitals, and that they all together determine the overall trend observed experimentally. Further NLMO analysis revealed a linear correlation between the contribution of the oxygen p_z lone pair orbital to the quadrupolar coupling constant and the strength of the halogen bond. This work, encompassing the first ¹⁷O SSNMR studies of halogen bonds, demonstrates how NMR observables provide a useful means to characterize halogen bonds and also improve our understanding of the correlation between the electronic structure of the halogen bond and NMR properties.