Sensing magnetic field and intermolecular interactions in diamagnetic solution using residual dipolar couplings of zephycandidine

Kowalczyk, R. M. ORCID: https://orcid.org/0000-0002-3926-6530, Murphy, P. J. and Tibble-Howlings, J. (2022) Sensing magnetic field and intermolecular interactions in diamagnetic solution using residual dipolar couplings of zephycandidine. International Journal of Molecular Sciences, 23 (23). 15118. ISSN 1422-0067 doi: 10.3390/ijms232315118

Abstract/Summary

An unusual residual dipolar coupling of methylene protons was recorded in NMR spectra because aromatic zephycandidine has preferential orientation at the external magnetic field. The observed splitting contains contribution from the dipole–dipole D-coupling and the anisotropic component of J-coupling. Absolute values of the anisotropy of magnetic susceptibility |∆χax| are larger for protic solvents because of the hydrogen-bonding compared to aprotic solvents for which polar and dispersion forces are more important. The energy barrier for the reorientation due to hydrogen-bonding is 1.22 kJ/mol in methanol-d4, 0.85 kJ/mol in ethanol-d6 and 0.87 kJ/mol in acetic acid-d6 . In dimethyl sulfoxide-d6 , 1.08 kJ/mol corresponds to the interaction of solvent lone pair electrons with π-electrons of zephycandidine. This energy barrier decreases for acetone-d6 which has smaller electric dipole moment. In acetonitrile-d3 , there is no energy barrier which suggests solvent ordering around the solute due to the solvent-solvent interactions. The largest absolute values of the magnetic anisotropy are observed for aromatic benezene-d6 and tolune-d8 which have their own preferential orientation and enhance the order in the solution. The magnetic anisotropy of “isolated” zephycandidine, not hindered by intermolecular interaction could be estimated from the correlation between ∆χax and cohesion energy density.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/109177
Identification Number/DOI	10.3390/ijms232315118
Refereed	Yes
Divisions	Interdisciplinary centres and themes > Chemical Analysis Facility (CAF) > NMR (CAF)
Publisher	MDPI
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