Small Molecule Mixture Analysis by Heteronuclear NMR under Spin Diffusion Conditions in Viscous DMSO–Water Solvent

Spin diffusion in NMR occurs for small- and medium-sized molecules when their tumbling rate reduces in solution so that magnetization exchange by longitudinal cross relaxation becomes highly efficient. Composite DMSO–water viscous solvents were used for the first time to access the individual NMR spectra of a mixture components in spin diffusion conditions. The easy handling and high dissolution power of [D6]DMSO/H2O offers a wide range of potential applications for polar and moderately apolar mixture analysis. In addition to 2D 1H-1H NOESY and 1H-13C HSQC-NOESY, 1H-15N HSQC-NOESY, 1D and 2D 1H-19F heteronuclear NOESY (HOESY) experiments were set up to offer new ways to individualize molecules within a mixture. This article reports the analysis of a polar mixture of four dipeptides dissolved in [D6]DMSO/H2O (7:3 v/v) and that of a medium-polarity fluorinated dinucleotide dissolved in [D6]DMSO/H2O (8:2 v/v) by means of spin diffusion in NOESY, HOESY, and HSQC–NOESY experiments.