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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

Experimental results for Molecule I.(a) Absorbance and CD chromatograms (obtained simultaneously) for samples of molecule I after being exposed to the REF for 83 h and subsequently collected. All process conditions were identical, except where noted. The first (left) peak of each chromatogram represents the leading half of the slug and the second (right) peak represents the trailing half of the slug. Upper: racemic molecule I after exposure to counterclockwise (CCW) REF. Middle: racemic molecule I after CW REF. Lower: pure S enantiomer of molecule I after CW REF. (b) Absorbance chromatogram from the in-line detector of a slug of racemic molecule I after exposure to CW REF for 45 h. The sample collected from the shaded left side of the chromatogram had ee of 26% of the S enantiomer of molecule I, while the right shaded section of the chromatogram had ee of 61% of the R enantiomer of molecule I. This is consistent with the edge of the sample slug being more enantiomerically enriched than in the centre. The boundaries of the active area of the separation chamber are also shown after conversion to the elution timescale.
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f3: Experimental results for Molecule I.(a) Absorbance and CD chromatograms (obtained simultaneously) for samples of molecule I after being exposed to the REF for 83 h and subsequently collected. All process conditions were identical, except where noted. The first (left) peak of each chromatogram represents the leading half of the slug and the second (right) peak represents the trailing half of the slug. Upper: racemic molecule I after exposure to counterclockwise (CCW) REF. Middle: racemic molecule I after CW REF. Lower: pure S enantiomer of molecule I after CW REF. (b) Absorbance chromatogram from the in-line detector of a slug of racemic molecule I after exposure to CW REF for 45 h. The sample collected from the shaded left side of the chromatogram had ee of 26% of the S enantiomer of molecule I, while the right shaded section of the chromatogram had ee of 61% of the R enantiomer of molecule I. This is consistent with the edge of the sample slug being more enantiomerically enriched than in the centre. The boundaries of the active area of the separation chamber are also shown after conversion to the elution timescale.

Mentions: To experimentally confirm the molecular propeller effect, we have performed experiments on solutions of molecules I and II using the experimental apparatus depicted in Fig. 2a. The REF inside the microfluidic chamber is generated by applying π/2 phase-shifted voltages to the four pairs of electrodes surrounding the chamber (Fig. 2b,c). A small amount of a racemic solution was injected into the centre of separation chamber and exposed to the REF. Data in Fig. 3a show that the materials collected from the leading and trailing sides of the exposed sample (which was split into two halves at the centre of the absorption chromatogram) have finite and opposite signs of circular dichroism (CD) signal. If the rotation direction of the REF is inverted, the CD signals from the leading and trailing fractions are inverted too. Furthermore, when the experiment is performed on a pure enantiomer sample, no inversion of the CD signal for leading and trailing fractions occurs; these results unequivocally prove that exposure to the REF leads to enantiomeric separation of binaphthyl molecules. Importantly, the experimentally detected direction of propulsion of S and R enantiomers is the same as predicted by MD simulations (compare signs of Lrev in Fig. 1c,d and CD signals in Fig. 3a and Supplementary Fig. 3a; for example, the leading fraction is enriched with the S enantiomer for the clockwise (CW) REF, see Fig. 3a middle panel). This offers a new approach for determining absolute configuration of a chiral molecule.


A molecular propeller effect for chiral separation and analysis.

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

Experimental results for Molecule I.(a) Absorbance and CD chromatograms (obtained simultaneously) for samples of molecule I after being exposed to the REF for 83 h and subsequently collected. All process conditions were identical, except where noted. The first (left) peak of each chromatogram represents the leading half of the slug and the second (right) peak represents the trailing half of the slug. Upper: racemic molecule I after exposure to counterclockwise (CCW) REF. Middle: racemic molecule I after CW REF. Lower: pure S enantiomer of molecule I after CW REF. (b) Absorbance chromatogram from the in-line detector of a slug of racemic molecule I after exposure to CW REF for 45 h. The sample collected from the shaded left side of the chromatogram had ee of 26% of the S enantiomer of molecule I, while the right shaded section of the chromatogram had ee of 61% of the R enantiomer of molecule I. This is consistent with the edge of the sample slug being more enantiomerically enriched than in the centre. The boundaries of the active area of the separation chamber are also shown after conversion to the elution timescale.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525176&req=5

f3: Experimental results for Molecule I.(a) Absorbance and CD chromatograms (obtained simultaneously) for samples of molecule I after being exposed to the REF for 83 h and subsequently collected. All process conditions were identical, except where noted. The first (left) peak of each chromatogram represents the leading half of the slug and the second (right) peak represents the trailing half of the slug. Upper: racemic molecule I after exposure to counterclockwise (CCW) REF. Middle: racemic molecule I after CW REF. Lower: pure S enantiomer of molecule I after CW REF. (b) Absorbance chromatogram from the in-line detector of a slug of racemic molecule I after exposure to CW REF for 45 h. The sample collected from the shaded left side of the chromatogram had ee of 26% of the S enantiomer of molecule I, while the right shaded section of the chromatogram had ee of 61% of the R enantiomer of molecule I. This is consistent with the edge of the sample slug being more enantiomerically enriched than in the centre. The boundaries of the active area of the separation chamber are also shown after conversion to the elution timescale.
Mentions: To experimentally confirm the molecular propeller effect, we have performed experiments on solutions of molecules I and II using the experimental apparatus depicted in Fig. 2a. The REF inside the microfluidic chamber is generated by applying π/2 phase-shifted voltages to the four pairs of electrodes surrounding the chamber (Fig. 2b,c). A small amount of a racemic solution was injected into the centre of separation chamber and exposed to the REF. Data in Fig. 3a show that the materials collected from the leading and trailing sides of the exposed sample (which was split into two halves at the centre of the absorption chromatogram) have finite and opposite signs of circular dichroism (CD) signal. If the rotation direction of the REF is inverted, the CD signals from the leading and trailing fractions are inverted too. Furthermore, when the experiment is performed on a pure enantiomer sample, no inversion of the CD signal for leading and trailing fractions occurs; these results unequivocally prove that exposure to the REF leads to enantiomeric separation of binaphthyl molecules. Importantly, the experimentally detected direction of propulsion of S and R enantiomers is the same as predicted by MD simulations (compare signs of Lrev in Fig. 1c,d and CD signals in Fig. 3a and Supplementary Fig. 3a; for example, the leading fraction is enriched with the S enantiomer for the clockwise (CW) REF, see Fig. 3a middle panel). This offers a new approach for determining absolute configuration of a chiral molecule.

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