Experimental and Theoretical ¹⁷O NMR Study of the Influence of Hydrogen-Bonding on CO and O−H Oxygens in Carboxylic Solids

Abstract

A systematic solid-state 17O NMR study of a series of carboxylic compounds, maleic acid, chloromaleic acid, KH maleate, KH chloromaleate, K2 chloromaleate, and LiH phthalate.MeOH, is reported. Magic-angle spinning (MAS), triple-quantum (3Q) MAS, and double angle rotation (DOR) 17O NMR spectra were recorded at high magnetic fields (14.1 and 18.8 T). 17O MAS NMR for metal-free carboxylic acids and metal-containing carboxylic salts show featured spectra and demonstrate that this combined, where necessary, with DOR and 3QMAS, can yield site-specific information for samples containing multiple oxygen sites. In addition to 17O NMR spectroscopy, extensive quantum mechanical calculations were carried out to explore the influence of hydrogen bonding at these oxygen sites. B3LYP/6-311G++(d,p) calculations of 17O NMR parameters yielded good agreement with the experimental values. Linear correlations are observed between the calculated 17O NMR parameters and the hydrogen bond strengths, suggesting the possibility of estimating H-bonding information from 17O NMR data. The calculations also revealed intermolecular H-bond effects on the 17O NMR shielding tensors. It is found that the delta11 and delta22 components of the chemical shift tensor at O-H and C=O, respectively, are aligned nearly parallel with the strong H-bond and shift away from this direction as the H-bond interaction weakens.

New Limits for Solid-State 17O NMR Spectroscopy: Complete Resolution of Multiple Oxygen Sites in a Simple Biomolecule

“…Similar metal induction of the shift was also observed for carboxylic oxygens. 13 Furthermore the quadrupole parameter, P Q , for O4 and O14 is ∼0.4 MHz smaller than that for the other oxygen sites, suggesting that the existence of O-Na interactions also increases the P Q values.Here, a novel NMR approach has characterized a multiple oxygen site system by using a combination of high-resolution 17 O DOR and 3Q MAS NMR experiments. The large shift range suggests that 17 O δ iso is highly sensitive to local environment around the different oxygen sites, for example, hydrogen bonds and ion interactions.…”

Ultra-high resolution 17O solid-state NMR spectroscopy of biomolecules: A comprehensive spectral analysis of monosodium L-glutamate·monohydrate

“…1 H, 13 C, 15 N and 29 Si. [1][2][3][4] This is because high spectral resolution of spin-½ systems can be obtained from routine In contrast the quadrupole interaction often significantly broadens the NMR signal of nuclei with spin > ½.…”

“…In particular, recent demonstrations on 17 O DOR spectroscopy have reported ultra-high spectral resolution with linewidths of <1 ppm). [15][16][17][18][19][20][21] It is worth noting that high-resolution 17 O NMR MQMAS and DOR have also been reported for many important inorganic materials. 5,[22][23][24] In comparison to inorganic materials, there are three major complications for 17 O solid-state NMR on bio/organic molecules: (1) the abundance of hydrogen in bio/organic molecules gives rise to significant dipolar broadening unless high power 1 H-decoupling is applied; (2) the quadrupole interaction is generally larger (7- 33 was used.…”

A neutron scattering study of strong-symmetric hydrogen bonds in potassium and cesium hydrogen bistrifluoroacetates: Determination of the crystal structures and of the single-well potentials for protons

“…The prototypical intramolecular strong-symmetric hydrogen bond ͑SSHB͒ in the crystal of potassium hydrogen maleate, KH͑OOC u CH v CH u COO͒ or KHM, has been thoroughly investigated with x-ray or neutron diffraction, [25][26][27] infrared and Raman, [28][29][30][31] inelastic neutron scattering ͑INS͒, 27,32-34 NMR, 35,36 and calorimetry. 37 The linear hydrogen bond is very short ͓R OO = 2.427͑1͒ Å at 5 K͔ and crystallographically symmetrical.…”