On the Observation of 14 N Quadrupole Resonance Transitions in Water Proton NMR Relaxometry Dispersion Curves: The Case of a Labile NH Grouping in a Semirigid Molecular Moiety

Sabine Bouguet-Bonnet (1) , Tristan Giraud (2) , Loic Stefan (2) , Marie-Christine Averlant-Petit (2) , Daniel Canet (3)

1 CRM2 - Cristallographie, Résonance Magnétique et Modélisations
2 LCPM - Laboratoire de Chimie Physique Macromoléculaire
3 LEMTA - Laboratoire d'Energétique et Mécanique Théorique et Appliquée

The frequencies of the three nitrogen-14 NQR transitions depend on both parameters but, for sensitivity reasons, their determination may be especially difficult and time consuming. For a partly rigid NH grouping with a labile proton, water NMR relaxometry curves may exhibit these three transitions (dubbed quadrupolar dips or QRE) provided that the NH grouping belongs to a moiety possessing a sufficient degree of ordering. Their lineshape leads to the correlation time describing mainly the motion of the NH grouping (the proton of which being in exchange with water protons), and their amplitude can be interpreted in terms of an effective NH distance. This approach is applied to an hydrogel, where separate NQR lines are observed for the different types of water existing in this system. Furthermore, the analysis of experimental data allows one to determine the nuclear quadrupole coupling in the protonated and deprotonated forms of this molecular moiety involving a labile NH grouping.

Mots clés: NMR relaxometry; quadrupolar tensor; asymmetry parameter; NH correlation time; NH distance; 14N NQR

Domaines: Chimie

Sabine Bouguet-Bonnet, Tristan Giraud, Loic Stefan, Marie-Christine Averlant-Petit, Daniel Canet. On the Observation of 14 N Quadrupole Resonance Transitions in Water Proton NMR Relaxometry Dispersion Curves: The Case of a Labile NH Grouping in a Semirigid Molecular Moiety. Journal of Physical Chemistry B, 2022, 126 (37), pp.7159-7165. ⟨10.1021/acs.jpcb.2c05208⟩. ⟨hal-03818616⟩