“Diffusion NMR of out-of-equilibrium mixtures”
Date:
Lecture / Seminar
Time: 09:30
Location: Perlman Chemical Sciences Building
Lecturer: Prof. Jean-Nicolas Dumez
Organizer: Department of Molecular Chemistry and Materials Science
Details: Universite de Nantes
Abstract:
The NMR spectra of molecular species in solution mixtures can be separated wit ... Read more
The NMR spectra of molecular species in solution mixtures can be separated with diffusion-ordered NMR spectroscopy (DOSY), a ‘virtual chromatography’ approach based on the measurement of translational diffusion coefficients. Classic DOSY experiments, however, require several minutes are not applicable to many important time-evolving mixtures.
Taking advantage of the concept of spatial encoding, we show here that DOSY data can be collected in a single scan of less than one second for several types of out-of-equilibrium mixtures. SPEN provides an acceleration of DOSY experiments by several orders of magnitude. SPEN DOSY pulse sequences are developed, that compensate for convection effects and are suitable for measurements in low-viscosity organic solvents, a requirement to monitor organic chemical reactions. We also show how to collect multiple consecutive scans from short-lived, non-renewable signals produced by dissolution dynamic nuclear polarisation (D-DNP), which is a versatile and powerful hyperpolarisation method. These methodological developments are supported by advanced numerical simulations, based on a Fokker-Plank formalism to describe simultaneously the spin and spatial dynamics. An exemple of hyperpolarised sample is given with a model mixture of small molecules, while the ability to monitor a reacting mixture is illustrated with a diamination reaction in dichloromethane.
The proposed UF DOSY methodology may contribute towards a real-time diffusion NMR analysis of mixtures, to help in the identification of a sample’s components and in the analysis of molecular interactions.
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