Laboratory of NMR Spectroscopy, Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland.
Phys Chem Chem Phys. 2018 Sep 12;20(35):22468-22476. doi: 10.1039/c8cp01748d.
Small amounts of water enriched in oxygen-17 were studied by 17O and 1H NMR in binary gaseous mixtures with Xe, Kr, CHF3 and CH3F and CO2. The distinct linear dependences of 17O and 1H chemical shifts and 1J(17O,1H) spin-spin coupling on the density of every gas solvent were measured. After the extrapolation of experimental results to zero density the relevant parameters in the isolated H217O molecule were determined. The same procedure was applied for H216O when its proton chemical shift was analyzed but the secondary isotope effect in the 1H shielding of H217O and H216O molecules was too small for detection. As shown, all the intermolecular effects in nuclear magnetic shielding are negative and these effects are more significant for 17O nuclei than for protons. It is consistent with the appropriate gas-to-liquid shifts of water which also indicate deshielding effects for both the investigated nuclei. On the other hand, the 1J0(17O,1H) coupling constant in H217O, which is completely free from intermolecular interactions, considerably differs from the 1J(17O,1H) experimental values obtained for water in liquid solutions. The present experimental data of the isolated H217O molecule are compared with selected results of shielding and spin-spin coupling calculations available from the literature and with the recent experimental data for a water molecule encapsulated in the C60 fullerene. Additionally, on the basis of actual results the magnetic dipole moment of the 17O nucleus is revalued for greater accuracy.
少量富氧-17 的水在 Xe、Kr、CHF3、CH3F 和 CO2 等二元气态混合物中，通过 17O 和 1H NMR 进行了研究。测量了 17O 和 1H 化学位移以及 1J(17O,1H)自旋-自旋偶合与每种气体溶剂密度的明显线性关系。将实验结果外推至零密度后，确定了孤立 H217O 分子中的相关参数。当分析 H216O 的质子化学位移时，采用了相同的程序，但 H217O 和 H216O 分子中 1H 屏蔽的次级同位素效应太小，无法检测到。结果表明，核磁共振屏蔽中的所有分子间效应均为负，并且这些效应对 17O 核的影响大于对质子的影响。这与水的适当气-液位移一致，也表明两个被研究的核都有去屏蔽效应。另一方面，在 H217O 中完全没有分子间相互作用的 1J0(17O,1H)偶合常数与在液态溶液中获得的水的 1J(17O,1H)实验值有很大差异。孤立 H217O 分子的本实验数据与文献中可用的屏蔽和自旋-自旋偶合计算的选定结果以及最近在 C60 富勒烯中封装的水分子的实验数据进行了比较。此外，基于实际结果，重新评估了 17O 核的磁偶极矩，以提高准确性。
