Influence of Magnetic Field on the Mobility of Aromatic Chiral Molecules

Abstract

The influence of magnetic fields on the properties of chiral molecules is of great interest nowadays. This work presents an (1)H NMR study of the mobility of 1-phenylethanol and 1-phenyl-1-propanol molecules in pure forms and in chirally polarized mixtures in external magnetic fields. Molecular mobility is shown to be dependent on the strength of the external magnetic field and chiral mixing. It could be assumed that the mobility changes are caused by rotational and magnetic interactions between induced magnetic moments of the aromatic molecules and the external magnetic field; intermolecular interactions are also essential. The results are important for the tasks related to enantiomer separation.

Separation of enantiomers by their enantiospecific interaction with achiral magnetic substrates

“…As can be realized from the data presented, the time scale to reach thermodynamics depends on the molecules and the experimental conditions, such as surface area versus concentration in the solution This is why the kinetics can actually be obtained only experimentally. We emphasize once again that the effect reported here is not associated with the direct interaction of chiral molecules with magnetic fields (31)(32)(33)(34) but rather with the magnetic-exchange interaction of the spin-polarized molecules with the spinpolarized substrate [see Figs. 1A, (v), and 4B].…”

Activation Parameters of Self-Diffusion of Aromatic Chiral Molecules in External Magnetic Fields

“…The increase of E values with increasing H 0 cannot be responsible for the ∼10 10 increment in D 0 if assuming that k 1 and k 2 remain constant with changes in magnetic field (Tables and ). Hence, it follows that variation of H 0 changes the type of mobility, which implicitly enters into parameters k 1 and k 2 , if using for analysis of the Arrhenius equation. − Such changes in self-diffusion of aromatic molecules can be related to the induced magnetic moments in aromatic molecules and their interactions with the external magnetic field. , The indicated interactions affect the orientation of the molecules, their hydrodynamic status, and the overall self-diffusion process, as was shown earlier …”

“…The racemate densities of 1-phenylethanol and 1-phenyl-1-propanol were 1.012 and 0.994 g/mL (25 °C), and the viscosities were 8.49 and 13.49 mPa s (25 °C), respectively. Mixtures were prepared by the addition of corresponding enantiomers to their racemates, as was done in refs and . These mixtures were described with the enantiomeric excess parameter ee = ( x R – x S )/( x R + x S ), where x R and x S are the concentration ratios of R and S molecules in the mixture (chiral polarized medium).…”

“…Despite the fact that chiral mixtures of 1-phenylethanol and 1-phenyl-1-propanol were used in the experiments, the separate spectral lines of 1 H NMR of the enantiomers were not observed. This is due to the weak effect of the chiral polarized mediums in the chemical shifts for 1 H nuclei. ,, …”

“…Earlier, it was shown that self-diffusion of aromatic chiral molecules (1-phenylethanol and 1-phenyl-1-propanol) in liquids depends on the magnetic field strength and concentration ratio of enantiomers. , In mixtures consisting of enantiomers, enantiomers may be surrounded by enantiomers of other chirality. The dynamic distribution of molecules must be different and depend on the concentration ratio of enantiomers in a liquid.…”