Investigation on the structure of liquid N-methylformamide-dimethylsulfoxide mixtures

The structures of liquid mixtures of N-methylformamide (NMF) and dimethyl sulfoxide (DMSO) at two concentrations (80% and 50% NMF) are investigated using a combination of neutron diffraction augmented with isotopic substitution and empirical potential structure refinement simulations. The results indicate that the NMF and DMSO molecules are hydrogen-bonded to one another with a preference for NMF-DMSO hydrogen bonding, compared to the NMF-NMF ones. The liquid is orientationally structured as a consequence of these hydrogen bonds between molecules. NMF-DMSO dimers are very stable species in the bulk of the mixture. The structure of the dimers is such that the angle between the molecular dipole moments is around 60°. The NMF molecules are well solvated in DMSO with potential implications for peptides solvation in this solvent.

Graphical abstractStructure of liquid NMF and DMSO mixtures investigated using a combination of neutron diffraction techniques augmented with isotopic substitution and empirical potential structure refinement simulations.Download full-size imageResearch highlights► NMF-DMSO mixture is a well-structured liquid. ► The liquid structure is driven by strong hydrogen bonds. ► There is a preference for NMF-DMSO hydrogen bonding compared to the NMF-NMF. ► There are very stable NMF-DMSO dimers dispersed through the liquid. ► The peptide structure is very well solvated in DMSO.