Molecular dynamics simulation study of the effect of single-walled carbon nanotube on the enantioseparation ability of a chiral ionic liquid

Abstract

A non-halogenated type of chiral ionic liquids (CIL's) called 1-butyl-3-methylimidazolium (T-4)-bis[(αS)-α-(hydroxy-O) benzeneacetato-κO] borate, [BMIm+] [BSMB−], has been used for enantioseparation of propranolol enantiomers. Experimental studies indicate that carbon nanotubes (CNT's) increase the Enantioselectivity of chiral ionic liquids through the enhancement of the interaction surface of chiral selectors with the compounds enantiomers. With the aim of investigating the mechanism under this observation, we used Molecular Dynamics (MD) Simulations to investigate the molecular level picture of the behavior of CIL and propranolol enantiomers on the Single-Walled Carbon Nanotube (SWCNT) surface. The density profiles, micro structure, radial distribution function, dimer existence autocorrelation function (DAF) and dynamic properties of propranolol enantiomers were studied in the CIL/CNT solution. The results are indicative of stronger interactions between R-propranolol enantiomers with CIL and CNT surface. Furthermore stronger interactions were seen between the R-propranolol molecules with one another. This leads to the difference in the replacement of propranolol enantiomers on the CNT surface in such a way that R-propranolol molecules propagate more along the CNT to have the maximum interactions with CIL molecules. The diffusion coefficient difference between S-propranolol and R-propranolol molecules shows a higher value in comparison to the system that CNT is absent. Consequently, the interactions, propagation and mobility of propranolol enantiomers are strongly influenced by CNT presence.