Q.E.COSY: determining sign and size of small deuterium residual quadrupolar couplings using an extended E.COSY principle

• Published in: Magnetic resonance in chemistry 2016-05, Vol.54 (5), p.351-357
• Main Authors: Tzvetkova, Pavleta, Luy, Burkhard
• Format: Article
• Language: English
• Subjects: 13C; Couplings; Deuterium; Dichroism; E.COSY; Liquid crystals; NMR; Nuclei; Phases; quadrupolar couplings; sign sensitivity; small coupling constants; Spectra; Spin 1; Splitting
• ISSN: 0749-1581; 1097-458X
• DOI: 10.1002/mrc.4386

Residual quadrupolar couplings contain important structural information comparable with residual dipolar couplings. However, the measurement of sign and size of especially small residual quadrupolar couplings is difficult. Here, we present an extension of the E.COSY principle to spin systems consisting of a Spin 1 coupled to a spin ½ nucleus, which allows the determination of the sign of the quadrupolar coupling of the Spin 1 nucleus relative to the heteronuclear coupling between the spins. The so‐called Q.E.COSY approach is demonstrated with its sign‐sensitivity using variable angle NMR, stretched gels and liquid crystalline phases applied to various CD and CD3 groups. Especially the sign‐sensitive measurement of residual quadrupolar couplings that remain unresolved in conventional deuterium 1D spectra is shown. Copyright © 2016 John Wiley & Sons, Ltd. The Q.E.COSY as an extension of the E.COSY principle allows the sign sensitive measurement of residual quadrupolar couplings in partially aligned samples even in cases where corresponding splittings are not resolved in the deuterium 1D spectrum. Several experimental demonstrations are given.