Solvent-induced enantioselectivity reversal in a chiral metal organic framework.

Benjamin D Slater,Bradley P Ladewig,Matthew R Hill

doi:10.1002/jssc.202100322

Abstract

Solvent-induced enantioselectivity reversal is a rarely reported phenomenon in porous homochiral materials. Similar behavior has been studied in chiral high performance liquid chromatography, where minor modifications to the mobile phase can induce elution order reversal of two enantiomers on a chiral stationary phase column. We report the first instance of solvent-induced enantioselectivity reversal in a homochiral metal organic framework. Further, we highlight the complex enantioselectivity behavior of homochiral metal organic frameworks toward racemic mixtures in the presence of solvents through racemate-solvent enantioselectivity and loading experiments as well as enantiopure-solvent loading experiments. We hypothesize that this interesting selectivity reversal behavior is likely to be observed in other competitive adsorption, nonchiral selective processes involving a solvent.

Highlights

Metal organic frameworks (MOFs) are an exciting class of porous materials consisting of metal ions or clusters coordinated to organic multivalent ligands to form multi-dimensional structures [1]
These materials can be engineered to allow lower energy separation processes toward enantiopure chemicals from racemic mixtures making them attractive candidates for industrial chiral separation processes
Vibrational circular dichroism coupled with density functional theory calculations were employed to investigate the enantioseparation of two chiral analytes on a cellulose and amylose column under chromatographic conditions

Summary

Introduction

Metal organic frameworks (MOFs) are an exciting class of porous materials consisting of metal ions or clusters coordinated to organic multivalent ligands to form multi-dimensional structures [1]. Solvent-induced enantioselectivity reversal in crystalline porous materials has been previously reported for a leucine-based cage material of the general formula M12L12, where the material preferentially adsorbed the (R) enantiomer of 2-methyl-2,4-pentanediol in methanol but the (S) enantiomer in heptane [25].

Results

Conclusion