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A molecular propeller effect for chiral separation and analysis.

Clemens JB, Kibar O, Chachisvilis M - Nat Commun (2015)

Bottom Line: Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions.We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion.We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light.

View Article: PubMed Central - PubMed

Affiliation: Dynamic Connections, LLC, 6150 Lusk Boulevard B104, San Diego, California 92121, USA.

ABSTRACT
Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved.

No MeSH data available.


Related in: MedlinePlus

Theoretical results.(a) Binapthyl molecule I (S enantiomer). Dipole moment, μ=5.3 Debye. (b) The mean square angular displacement of molecule I around three different molecular rotation axes. (c–e) Displacement of the centre of mass of the molecule along a specified axis versus the angle of rotation around the same axis (only part of the trajectory is shown to reduce the number of points on the graph). Each data point represents a time step of 250 fs. (c,e) S enantiomer. (d) R enantiomer. Red lines indicate linear regression fit to the data. Slope values (c) 1.22±0.03 Å, (d) −1.18±0.03 Å, (e) −0.02±0.03 Å per 360 deg revolution (mean±s.e.m.). (f) Distribution of molecules as a function of the angle between the external electric field and the dipole moment of the molecule (α), plotted for four different values of dipole moment—electric field interaction energies. Molecules above the dashed line represent the ‘responding' fraction of the molecules that respond to changes in electric field direction. (g) The dependence of the expected propeller velocity on relative electric field magnitude calculated according to equation (4) for the following parameters: molecule rotation frequency, νeff=0.9 MHz, displacement per one revolution, Lrev=1.2 Å.
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f1: Theoretical results.(a) Binapthyl molecule I (S enantiomer). Dipole moment, μ=5.3 Debye. (b) The mean square angular displacement of molecule I around three different molecular rotation axes. (c–e) Displacement of the centre of mass of the molecule along a specified axis versus the angle of rotation around the same axis (only part of the trajectory is shown to reduce the number of points on the graph). Each data point represents a time step of 250 fs. (c,e) S enantiomer. (d) R enantiomer. Red lines indicate linear regression fit to the data. Slope values (c) 1.22±0.03 Å, (d) −1.18±0.03 Å, (e) −0.02±0.03 Å per 360 deg revolution (mean±s.e.m.). (f) Distribution of molecules as a function of the angle between the external electric field and the dipole moment of the molecule (α), plotted for four different values of dipole moment—electric field interaction energies. Molecules above the dashed line represent the ‘responding' fraction of the molecules that respond to changes in electric field direction. (g) The dependence of the expected propeller velocity on relative electric field magnitude calculated according to equation (4) for the following parameters: molecule rotation frequency, νeff=0.9 MHz, displacement per one revolution, Lrev=1.2 Å.

Mentions: We introduce hydrodynamic chirality to characterize the direction and magnitude of propeller-like motion of a molecule. The dipole moments of the selected binaphthyl molecules are parallel to the C2 symmetry axes (which is aligned along the I2 axis in Fig. 1a). An applied external electric field will impose a torque around any axis in the coordinate plane containing I1 and I3 axes (Fig. 1a) depending on the spatial orientation of the molecule. On the basis of symmetry considerations, it is expected that rotation around the I1 axis will propel the molecule because of the propeller effect, while rotation around the I3 axis (aligned along internaphthyl bond) should not lead to significant propulsion. Owing to random orientations of the molecules in solution with respect to the plane of the REF, the molecule on average will rotate around all possible axes in the I1 and I3 planes. On the basis of a simple hydrodynamic picture, the propulsion direction for a rotating binaphthyl critically depends on the dihedral angle between naphthyl moieties—similar to propeller blades. Therefore, the propulsion direction is expected to be of the opposite sign for different absolute configurations S and R.


A molecular propeller effect for chiral separation and analysis.

Clemens JB, Kibar O, Chachisvilis M - Nat Commun (2015)

Theoretical results.(a) Binapthyl molecule I (S enantiomer). Dipole moment, μ=5.3 Debye. (b) The mean square angular displacement of molecule I around three different molecular rotation axes. (c–e) Displacement of the centre of mass of the molecule along a specified axis versus the angle of rotation around the same axis (only part of the trajectory is shown to reduce the number of points on the graph). Each data point represents a time step of 250 fs. (c,e) S enantiomer. (d) R enantiomer. Red lines indicate linear regression fit to the data. Slope values (c) 1.22±0.03 Å, (d) −1.18±0.03 Å, (e) −0.02±0.03 Å per 360 deg revolution (mean±s.e.m.). (f) Distribution of molecules as a function of the angle between the external electric field and the dipole moment of the molecule (α), plotted for four different values of dipole moment—electric field interaction energies. Molecules above the dashed line represent the ‘responding' fraction of the molecules that respond to changes in electric field direction. (g) The dependence of the expected propeller velocity on relative electric field magnitude calculated according to equation (4) for the following parameters: molecule rotation frequency, νeff=0.9 MHz, displacement per one revolution, Lrev=1.2 Å.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4525176&req=5

f1: Theoretical results.(a) Binapthyl molecule I (S enantiomer). Dipole moment, μ=5.3 Debye. (b) The mean square angular displacement of molecule I around three different molecular rotation axes. (c–e) Displacement of the centre of mass of the molecule along a specified axis versus the angle of rotation around the same axis (only part of the trajectory is shown to reduce the number of points on the graph). Each data point represents a time step of 250 fs. (c,e) S enantiomer. (d) R enantiomer. Red lines indicate linear regression fit to the data. Slope values (c) 1.22±0.03 Å, (d) −1.18±0.03 Å, (e) −0.02±0.03 Å per 360 deg revolution (mean±s.e.m.). (f) Distribution of molecules as a function of the angle between the external electric field and the dipole moment of the molecule (α), plotted for four different values of dipole moment—electric field interaction energies. Molecules above the dashed line represent the ‘responding' fraction of the molecules that respond to changes in electric field direction. (g) The dependence of the expected propeller velocity on relative electric field magnitude calculated according to equation (4) for the following parameters: molecule rotation frequency, νeff=0.9 MHz, displacement per one revolution, Lrev=1.2 Å.
Mentions: We introduce hydrodynamic chirality to characterize the direction and magnitude of propeller-like motion of a molecule. The dipole moments of the selected binaphthyl molecules are parallel to the C2 symmetry axes (which is aligned along the I2 axis in Fig. 1a). An applied external electric field will impose a torque around any axis in the coordinate plane containing I1 and I3 axes (Fig. 1a) depending on the spatial orientation of the molecule. On the basis of symmetry considerations, it is expected that rotation around the I1 axis will propel the molecule because of the propeller effect, while rotation around the I3 axis (aligned along internaphthyl bond) should not lead to significant propulsion. Owing to random orientations of the molecules in solution with respect to the plane of the REF, the molecule on average will rotate around all possible axes in the I1 and I3 planes. On the basis of a simple hydrodynamic picture, the propulsion direction for a rotating binaphthyl critically depends on the dihedral angle between naphthyl moieties—similar to propeller blades. Therefore, the propulsion direction is expected to be of the opposite sign for different absolute configurations S and R.

Bottom Line: Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions.We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion.We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light.

View Article: PubMed Central - PubMed

Affiliation: Dynamic Connections, LLC, 6150 Lusk Boulevard B104, San Diego, California 92121, USA.

ABSTRACT
Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved.

No MeSH data available.


Related in: MedlinePlus