Asymmetric Molecules and Chirality Recognition

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Chemistry: Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 26591

Special Issue Editors


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Guest Editor
Department of Physical Chemistry, Faculty of Science, University of Valladolid, 47011 Valladolid, Spain
Interests: molecular spectroscopy; water clusters; hydrogen-bonding; chirality

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Guest Editor
CFisUC, Department of Physics, University of Coimbra, 3004-516 Coimbra, Portugal
Interests: molecular physics; chiral recognition; molecular and chiroptical spectroscopies

E-Mail Website
Guest Editor
Department of Physical Chemistry, Faculty of Science, University of Valladolid, 47011 Valladolid, Spain
Interests: microwave spectroscopy and its applications to chirality; instrument development; astrochemistry; polycyclic aromatic hydrocarbons and their chemistry

Special Issue Information

Dear Colleagues,

Symmetry is a concept with immense implications for the way we interpret the universe and its properties. In this realm, chirality is ubiquitous and can be observed at the subatomic, supramolecular, and galactic scales. Strikingly, asymmetric molecules carry tremendous importance in the way biological matter is structured. The origin of biological homochirality is still an open debate, and it eludes us in many aspects. To tackle several of the most pressing open questions linked to breaks in symmetry and chiral structures, an increasing number of experimental techniques are being developed that can capture and retrieve precise quantitative information on chiral molecules, either in isolation or in condensed phases. This endeavor is crucial, as chiral probes are essential for improving design and separation methods in an increasingly fast-paced scientific enterprise.

The aim of this Special Issue is to bring together the old and the new in experimental methodologies for chiral analysis and separation, spanning molecular to supramolecular research domains, thus stimulating a stronger synergy between complementary tools to recover chiral information.

With this mindset, we call on our peers for contributions (short communications, research, and review articles) on topics related to chirality at the molecular scale, covering a broad range of technical methods employed to detect, interrogate, analyse, and separate chiral molecules in all phases of matter.

Dr. Cristóbal Pérez
Dr. Sérgio R. Domingos
Dr. Amanda Steber
Guest Editors

Manuscript Submission Information

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Keywords

  • chiral molecules
  • absolute configuration
  • stereochemistry
  • enantiomers
  • chiroptical spectroscopy
  • circular spectropolarimetry
  • chiral separation
  • chiral chromatography
  • optical rotation
  • rotational spectroscopy
  • infrared spectroscopy
  • vibrational circular dichroism
  • Raman optical activity
  • gas-phase spectroscopies
  • molecular beams
  • photoelectron circular dichroism
  • Coulomb explosion
  • molecular recognition
  • enantiomeric excess
  • mixture analysis
  • NMR
  • asymmetric synthesis
  • parity violation
  • non-linear optical processes
  • circularly polarised luminescence
  • MOFs
  • emergent technologies

Published Papers (10 papers)

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Research

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12 pages, 9104 KiB  
Article
A Scent of Peppermint—A Microwave Spectroscopy Analysis on the Composition of Peppermint Oil
by Anna Krin, María Mar Quesada Moreno, Cristóbal Pérez and Melanie Schnell
Symmetry 2022, 14(6), 1262; https://doi.org/10.3390/sym14061262 - 18 Jun 2022
Cited by 3 | Viewed by 2358
Abstract
Essential oils have a vast number of applications in different areas of our daily life. Detailed chiral analysis and structural characterization of their constituents remains an important subject in analytical chemistry. Here, we report on a broadband rotational spectroscopy study of peppermint oil [...] Read more.
Essential oils have a vast number of applications in different areas of our daily life. Detailed chiral analysis and structural characterization of their constituents remains an important subject in analytical chemistry. Here, we report on a broadband rotational spectroscopy study of peppermint oil in the frequency range 2–8 GHz. We focus on an unambiguous determination of the excess enantiomers of the oil constituents menthone and isomenthone in the oil by applying chirality-sensitive rotational spectroscopy, the so-called microwave three-wave mixing (M3WM) technique. Additionally, a new menthol conformer, not previously characterized, was experimentally observed, and the gas-phase structures of the two conformers of menthol and menthone were determined experimentally based on the assignment of their 13C-isotopologues in natural abundance. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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12 pages, 2662 KiB  
Article
MCD and Induced CD of a Tetraphenoxyperylene-Based Dye in Chiral Solvents: An Experimental and Computational Study
by Simone Ghidinelli, Marco Fusè, Giuseppe Mazzeo, Sergio Abbate and Giovanna Longhi
Symmetry 2022, 14(6), 1108; https://doi.org/10.3390/sym14061108 - 28 May 2022
Cited by 2 | Viewed by 2226
Abstract
The magnetic circular dichroism (MCD) spectrum of N,N′-bis(2,6-diisopropylphenyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxydiimide, also known as Lumogen Red 300 or ROT-300, has been recorded both in achiral and chiral solvents. The induced CD spectra in chiral solvents have, similarly, been recorded. A discussion of the spectroscopic response, both [...] Read more.
The magnetic circular dichroism (MCD) spectrum of N,N′-bis(2,6-diisopropylphenyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxydiimide, also known as Lumogen Red 300 or ROT-300, has been recorded both in achiral and chiral solvents. The induced CD spectra in chiral solvents have, similarly, been recorded. A discussion of the spectroscopic response, both in CD and in MCD experiments, is presented in this paper. Both types of spectra have been predicted most satisfactorily by DFT calculations; the CD spectra were obtained by assuming the prevalence of one “enantiomeric” conformer and the same set of conformers could also be used for MCD, since “enantiomeric” structures present identically in MCD spectra. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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14 pages, 2150 KiB  
Article
Accurate Determination of Enantiomeric Excess Using Raman Optical Activity
by Pavel Michal, Jana Hudecová, Radek Čelechovský, Milan Vůjtek, Michal Dudka and Josef Kapitán
Symmetry 2022, 14(5), 990; https://doi.org/10.3390/sym14050990 - 12 May 2022
Cited by 5 | Viewed by 2134
Abstract
The optical purity of a chiral sample is of particular importance to the analytical chemistry and pharmaceutical industries. In recent years, the vibrational optical activity (VOA) has become established as a sensitive and nondestructive technique for the analysis of chiral molecules in solution. [...] Read more.
The optical purity of a chiral sample is of particular importance to the analytical chemistry and pharmaceutical industries. In recent years, the vibrational optical activity (VOA) has become established as a sensitive and nondestructive technique for the analysis of chiral molecules in solution. However, the relatively limited accuracy in the range of about 1–2% reported in published papers and the relatively small spread of experimental facilities to date have meant that vibrational spectroscopy has not been considered a common method for determining enantiomeric excess. In this paper, we attempt to describe, in detail, a methodology for the determination of enantiomeric excess using Raman optical activity (ROA). This method achieved an accuracy of 0.05% for neat α-pinene and 0.22% for alanine aqueous solution, after less than 6 h of signal accumulation for each enantiomeric mixture, which we believe is the best result achieved to date using vibrational optical activity techniques. An algorithm for the elimination of systematic errors (polarization artifacts) is proposed, and the importance of normalizing ROA spectra to correct for fluctuations in excitation power is established. Results comparable to those obtained with routinely used chemometric analysis by the partial least squares (PLS) method were obtained. These findings show the great potential of ROA spectroscopy for the quantitative analysis of enantiomeric mixtures. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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10 pages, 1955 KiB  
Article
Chiral Analysis of Linalool, an Important Natural Fragrance and Flavor Compound, by Molecular Rotational Resonance Spectroscopy
by Reilly E. Sonstrom, Donald M. Cannon and Justin L. Neill
Symmetry 2022, 14(5), 917; https://doi.org/10.3390/sym14050917 - 30 Apr 2022
Cited by 7 | Viewed by 2740
Abstract
The chiral analysis of terpenes in complex mixtures of essential oils, necessary for authentication, has been further developed using chiral tagging molecular rotational resonance (MRR) spectroscopy. One analyte that is of particular interest is linalool (3,7-dimethyl-1,6-octadien-3-ol), a common natural chiral terpene found in [...] Read more.
The chiral analysis of terpenes in complex mixtures of essential oils, necessary for authentication, has been further developed using chiral tagging molecular rotational resonance (MRR) spectroscopy. One analyte that is of particular interest is linalool (3,7-dimethyl-1,6-octadien-3-ol), a common natural chiral terpene found in botanicals with its enantiomers having unique flavor, fragrance, and aromatherapy characteristics. In this MRR demonstration, resolution of the enantiomers is achieved through the addition of a chiral tag, which creates non-covalent diastereomeric complexes with distinct spectral signatures. The relative stereochemistry of the complexes is identified by the comparison of calculated spectroscopic parameters with experimentally determined parameters of the chiral complexes with high accuracy. The diastereomeric complex intensities are analyzed to determine the absolute configuration (AC) and enantiomeric excess (EE) in each sample. Here, we demonstrate the use of chiral tagging MRR spectroscopy to perform a quantitative routine enantiomer analysis of linalool in complex essential oil mixtures, without the need for reference samples or chromatographic separation. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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17 pages, 4881 KiB  
Article
Rational Pulse Design for Enantiomer-Selective Microwave Three-Wave Mixing
by Monika Leibscher, Jonas Kalveram and Christiane P. Koch
Symmetry 2022, 14(5), 871; https://doi.org/10.3390/sym14050871 - 24 Apr 2022
Cited by 4 | Viewed by 2320
Abstract
Microwave three-wave mixing allows for enantiomer-selective excitation of randomly oriented chiral molecules into rotational states with different energy. The random orientation of molecules is reflected in the degeneracy of the rotational spectrum with respect to the orientational quantum number M and reduces, if [...] Read more.
Microwave three-wave mixing allows for enantiomer-selective excitation of randomly oriented chiral molecules into rotational states with different energy. The random orientation of molecules is reflected in the degeneracy of the rotational spectrum with respect to the orientational quantum number M and reduces, if not accounted for, enantiomer-selectivity. Here, we show how to design pulse sequences with maximal enantiomer-selectivity from an analysis of the M-dependence of the Rabi frequencies associated with rotational transitions induced by resonant microwave drives. We compare different excitations schemes for rotational transitions and show that maximal enantiomer-selectivity at a given rotational temperature is achieved for synchronized three-wave mixing with circularly polarized fields. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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13 pages, 3721 KiB  
Article
Construction and Demonstration of a 6–18 GHz Microwave Three-Wave Mixing Experiment Using Multiple Synchronized Arbitrary Waveform Generators
by Nicole T. Moon, Klaus Woelk and Garry S. Grubbs II
Symmetry 2022, 14(5), 848; https://doi.org/10.3390/sym14050848 - 19 Apr 2022
Cited by 2 | Viewed by 3356
Abstract
This manuscript details the construction and demonstration of the first known microwave three-wave mixing (M3WM) experiment utilizing multiple arbitrary waveform generators (AWGs) completely operable in the 6–18 GHz frequency range for use in chirality determination and quantification. Many M3WM techniques, which involve two [...] Read more.
This manuscript details the construction and demonstration of the first known microwave three-wave mixing (M3WM) experiment utilizing multiple arbitrary waveform generators (AWGs) completely operable in the 6–18 GHz frequency range for use in chirality determination and quantification. Many M3WM techniques, which involve two orthogonal, subsequent Rabi π/2 and π microwave pulses, suffer from flexibility in pulse types and timings as well as frequency due to most instruments only using one, one-channel AWG and the M3WM probability decreasing with an increasing quantum number, J. In this work, we presented an M3WM instrument that allows that flexibility by introducing multiple, synchronized AWGs and adheres to the high probability transition loop pathways in carvone. The functionality and reliability of the instrument were demonstrated using a series of experiments and mixtures of the R and S enantiomers and determined to be of similar accuracy to other reported M3WM setups with the additional benefit of flexibility in pulsing schemes. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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19 pages, 1220 KiB  
Article
Attaching Onto or Inserting Into an Intramolecular Hydrogen Bond: Exploring and Controlling a Chirality-Dependent Dilemma for Alcohols
by Manuel Lange, Elisabeth Sennert and Martin A. Suhm
Symmetry 2022, 14(2), 357; https://doi.org/10.3390/sym14020357 - 11 Feb 2022
Cited by 3 | Viewed by 2173
Abstract
Prereactive complexes in noncovalent organocatalysis are sensitive to the relative chirality of the binding partners and to hydrogen bond isomerism. Both effects are present when a transiently chiral alcohol docks on a chiral α-hydroxy ester, turning such 1:1 complexes into elementary, non-reactive [...] Read more.
Prereactive complexes in noncovalent organocatalysis are sensitive to the relative chirality of the binding partners and to hydrogen bond isomerism. Both effects are present when a transiently chiral alcohol docks on a chiral α-hydroxy ester, turning such 1:1 complexes into elementary, non-reactive model systems for chirality induction in the gas phase. With the help of linear infrared and Raman spectroscopy in supersonic jet expansions, conformational preferences are investigated for benzyl alcohol in combination with methyl lactate, also exploring p-chlorination of the alcohol and the achiral homolog methyl glycolate to identify potential London dispersion and chirality effects on the energy sequence. Three of the four combinations prefer barrierless complexation via the hydroxy group of the ester (association). In contrast, the lightest complex predominantly shows insertion into the intramolecular hydrogen bond, such as the analogous lactate and glycolate complexes of methanol. The experimental findings are rationalized with computations, and a uniform helicality induction in the alcohol by the lactate is predicted, independent of insertion into or association with the internal lactate hydrogen bond. p-chlorination of benzyl alcohol has a stabilizing effect on association because the insertion motif prevents a close contact between the chlorine and the hydroxy ester. After simple anharmonicity and substitution corrections, the B3LYP-D3 approach offers a fairly systematic description of the known spectroscopic data on alcohol complexes with α-hydroxy esters. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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10 pages, 1600 KiB  
Article
Sub-Hz Differential Rotational Spectroscopy of Enantiomers
by Lincoln Satterthwaite, Greta Koumarianou, Daniel Sorensen and David Patterson
Symmetry 2022, 14(1), 28; https://doi.org/10.3390/sym14010028 - 27 Dec 2021
Cited by 5 | Viewed by 2693
Abstract
We demonstrate for the first time high-precision differential microwave spectroscopy, achieving sub-Hz precision by coupling a cryogenic buffer gas cell with a tunable microwave Fabry–Perot cavity. We report statistically limited sub-Hz precision of (0.08 ± 0.72) Hz, observed between enantiopure samples of (R)-1,2-propanediol [...] Read more.
We demonstrate for the first time high-precision differential microwave spectroscopy, achieving sub-Hz precision by coupling a cryogenic buffer gas cell with a tunable microwave Fabry–Perot cavity. We report statistically limited sub-Hz precision of (0.08 ± 0.72) Hz, observed between enantiopure samples of (R)-1,2-propanediol and (S)-1,2-propanediol at frequencies near 15 GHz. We confirm highly repeatable spectroscopic measurements compared to traditional pulsed-jet methods, opening up new capabilities in probing subtle molecular structural effects at the 10−10 level and providing a platform for exploring sources of systematic error in parity-violation searches. We discuss dominant systematic effects at this level and propose possible extensions of the technique for higher precision. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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13 pages, 1680 KiB  
Article
Molecular Recognition, Transient Chirality and Sulfur Hydrogen Bonding in the Benzyl Mercaptan Dimer
by Rizalina Tama Saragi, Marcos Juanes, Ruth Pinacho, José Emiliano Rubio, José A. Fernández and Alberto Lesarri
Symmetry 2021, 13(11), 2022; https://doi.org/10.3390/sym13112022 - 26 Oct 2021
Cited by 11 | Viewed by 2154
Abstract
The homodimers of transiently chiral molecules offer physical insight into the process of molecular recognition, the preference for homo or heterochiral aggregation and the nature of the non-covalent interactions stabilizing the adducts. We report the observation of the benzyl mercaptan dimer in the [...] Read more.
The homodimers of transiently chiral molecules offer physical insight into the process of molecular recognition, the preference for homo or heterochiral aggregation and the nature of the non-covalent interactions stabilizing the adducts. We report the observation of the benzyl mercaptan dimer in the isolation conditions of a supersonic jet expansion, using broadband (chirped-pulse) microwave spectroscopy. A single homochiral isomer was observed for the dimer, stabilized by a cooperative sequence of S-H···S and S-H···π hydrogen bonds. The structural data, stabilization energies and energy decomposition describe these non-covalent interactions as weak and dispersion-controlled. A comparison is also provided with the benzyl alcohol dimer. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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Review

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13 pages, 3012 KiB  
Review
How Symmetry Influences the Dissociation of Protonated Cyclic Peptides
by Ariel F. Pérez-Mellor, Riccardo Spezia and Anne Zehnacker
Symmetry 2022, 14(4), 679; https://doi.org/10.3390/sym14040679 - 25 Mar 2022
Cited by 4 | Viewed by 2141
Abstract
Protonated cyclic dipeptides undergo collision-induced dissociation, and this reaction mechanism strongly depends on the symmetry and the nature of the residues. We review the main dissociation mechanism for a series of cyclic dipeptides, obtained through chemical dynamics simulations. The systems range from the [...] Read more.
Protonated cyclic dipeptides undergo collision-induced dissociation, and this reaction mechanism strongly depends on the symmetry and the nature of the residues. We review the main dissociation mechanism for a series of cyclic dipeptides, obtained through chemical dynamics simulations. The systems range from the symmetrical cyclo-(glycyl-glycyl), with two possible symmetrical protonation sites located on the peptide ring, to cyclo-(tyrosyl-prolyl), where the symmetry of protonation sites on the peptide ring is broken by the dissimilar nature of the different residues. Finally, cyclo-(phenylalanyl-histidyl) shows a completely asymmetric situation, with the proton located on one of the dipeptide side chains, which explains the peculiar fragmentation mechanism induced by shuttling the proton, whose efficiency is strongly dependent on the relative chirality of the residues. Full article
(This article belongs to the Special Issue Asymmetric Molecules and Chirality Recognition)
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