1
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Schmahl S, Horn F, Jin J, Westphal H, Belder D, Asmis KR. Online-Monitoring of the Enantiomeric Ratio in Microfluidic Chip Reactors Using Chiral Selector Ion Vibrational Spectroscopy. Chemphyschem 2024; 25:e202300975. [PMID: 38418402 DOI: 10.1002/cphc.202300975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/23/2024] [Accepted: 02/23/2024] [Indexed: 03/01/2024]
Abstract
A novel experimental approach for the rapid online monitoring of the enantiomeric ratio of chiral analytes in solution is presented. The charged analyte is transferred to the gas phase by electrospray. Diastereomeric complexes are formed with a volatile chiral selector in a buffer-gas-filled ion guide held at room temperature, mass-selected, and subsequently spectrally differentiated by cryogenic ion trap vibrational spectroscopy. Based on the spectra of the pure complexes in a small diastereomer-specific spectral range, the composition of diastereomeric mixtures is characterized using the cosine similarity score, from which the enantiomeric ratio in the solution is determined. The method is demonstrated for acidified alanine solutions and using three different chiral selectors (2-butanol, 1-phenylethanol, 1-amino-2-propanol). Among these, 2-butanol is the best choice as a selector for protonated alanine, also because the formation ratio of the corresponding diastereomeric complexes is found to be independent of the nature of the enantiomer. Subsequently, a microfluidic chip is implemented to mix enantiomerically pure alanine solutions continuously and determine the enantiomeric ratio online with minimal sample consumption within one minute and with competitive accuracy.
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Affiliation(s)
- Sonja Schmahl
- Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstraße 2, 04103, Leipzig, Germany
| | - Francine Horn
- Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstraße 2, 04103, Leipzig, Germany
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Jiaye Jin
- Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstraße 2, 04103, Leipzig, Germany
| | - Hannes Westphal
- Institut für Analytische Chemie, Universität Leipzig, Linnéstraße 3, 04103, Leipzig, Germany
| | - Detlev Belder
- Institut für Analytische Chemie, Universität Leipzig, Linnéstraße 3, 04103, Leipzig, Germany
| | - Knut R Asmis
- Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstraße 2, 04103, Leipzig, Germany
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2
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De Waele DJS, Luyten S, Sonstrom RE, Bogaerts J, Neill JL, Viereck P, Goossens K, Baeten M, Vervoort N, Herrebout W. Absolute configuration assignment of highly fluorinated carboxylic acids via VCD and MRR spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 306:123625. [PMID: 37950934 DOI: 10.1016/j.saa.2023.123625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 10/25/2023] [Accepted: 11/05/2023] [Indexed: 11/13/2023]
Abstract
Chiral analysis has become a crucial step in studying the stereospecific synthesis of Active Pharmaceutical Ingredients (APIs). Both Vibrational Circular Dichroism (VCD) and Molecular Rotational Resonance (MRR) spectroscopy are capable of determining absolute configurations (ACs) via comparison of experimental and calculated data. In this regard, each technique has its own caveats. In VCD analysis, accurate prediction of the normal modes as well as rigorous conformational searches of both the analyte and potential (self-)aggregation products are required to optimally match experimental spectra. In MRR analysis, chiral species are resolved through complexation with a chiral tag to prepare spectrally distinct diastereomeric complexes. Although individual complex isomers can be distinguished, spectral assignments need to be matched to unique isomer geometries for unambiguous AC assignment. In this work, the ACs of two highly fluorinated carboxylic acids were successfully assigned using VCD and MRR spectroscopy. In the VCD analysis, the M06-2X functional was demonstrated to be superior to B3LYP and B3LYP-GD3 in accurately predicting the C-F normal modes and both monomeric and dimeric spectral contributions were observed. In a similar analysis with broadband MRR, most experimentally identified geometries had more than one possible computational match. Nevertheless, careful consideration of the chiral tag, as well as additional isomer assignments, resulted in successful assignment of the AC. This comparative study demonstrates the power of contemporary VCD analysis and the unique contributions of MRR to the analytical toolbox.
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Affiliation(s)
- Dimitri J S De Waele
- Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Sjobbe Luyten
- Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Reilly E Sonstrom
- BrightSpec, Inc., 770 Harris Street Suite 104b, Charlottesville, VA 22903, United States
| | - Jonathan Bogaerts
- Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Justin L Neill
- BrightSpec, Inc., 770 Harris Street Suite 104b, Charlottesville, VA 22903, United States
| | - Peter Viereck
- Chemical Process R&D, Discovery Process Research, Janssen R&D, Turnhoutseweg 30, B-2340 Beerse, Belgium
| | - Karel Goossens
- Chemical Process R&D, Process Analytical Research, Janssen R&D, Turnhoutseweg 30, B-2340 Beerse, Belgium
| | - Mattijs Baeten
- Chemical Process R&D, Process Analytical Research, Janssen R&D, Turnhoutseweg 30, B-2340 Beerse, Belgium
| | - Nico Vervoort
- Chemical Process R&D, Process Analytical Research, Janssen R&D, Turnhoutseweg 30, B-2340 Beerse, Belgium
| | - Wouter Herrebout
- Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
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3
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Vang ZP, Sonstrom RE, Scolati HN, Clark JR, Pate BH. Assignment of the absolute configuration of molecules that are chiral by virtue of deuterium substitution using chiral tag molecular rotational resonance spectroscopy. Chirality 2023; 35:856-883. [PMID: 37277968 PMCID: PMC11102577 DOI: 10.1002/chir.23596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 05/10/2023] [Accepted: 05/16/2023] [Indexed: 06/07/2023]
Abstract
Chiral tag molecular rotational resonance (MRR) spectroscopy is used to assign the absolute configuration of molecules that are chiral by virtue of deuterium substitution. Interest in the improved performance of deuterated active pharmaceutical ingredients has led to the development of precision deuteration reactions. These reactions often generate enantioisotopomer reaction products that pose challenges for chiral analysis. Chiral tag rotational spectroscopy uses noncovalent derivatization of the enantioisotopomer to create the diastereomers of the 1:1 molecular complexes of the analyte and a small, chiral molecule. Assignment of the absolute configuration requires high-confidence determinations of the structures of these weakly bound complexes. A general search method, CREST, is used to identify candidate geometries. Subsequent geometry optimization using dispersion corrected density functional theory gives equilibrium geometries with sufficient accuracy to identify the isomers of the chiral tag complexes produced in the pulsed jet expansion used to introduce the sample into the MRR spectrometer. Rotational constant scaling based on the fact that the diastereomers have the same equilibrium geometry gives accurate predictions allowing identification of the homochiral and heterochiral tag complexes and, therefore, assignment of absolute configuration. The method is successfully applied to three oxygenated substrates from enantioselective Cu-catalyzed alkene transfer hydrodeuteration reaction chemistry.
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Affiliation(s)
- Zoua Pa Vang
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin, USA
| | - Reilly E. Sonstrom
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
- BrightSpec Inc, Charlottesville, Virginia, USA
| | - Haley N. Scolati
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
| | - Joseph R. Clark
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin, USA
| | - Brooks H. Pate
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
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4
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Ebrahimi M, Norouzi P, Ghasemi JB, Moosavi-Movahedi AA, Noroozifar M, Salahandish R. Advancing chirality analysis through enhanced enantiomer characterization and quantification via fast Fourier transform capacitance voltammetry. Sci Rep 2023; 13:16739. [PMID: 37798351 PMCID: PMC10556018 DOI: 10.1038/s41598-023-43945-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 09/30/2023] [Indexed: 10/07/2023] Open
Abstract
The exploration of the chiral configurations of enantiomers represents a highly intriguing realm of scientific inquiry due to the distinct roles played by each enantiomer (D and L) in chemical reactions and their practical utilities. This study introduces a pioneering analytical methodology, termed fast Fourier transform capacitance voltammetry (FFT-CPV), in conjunction with principal component analysis (PCA), for the identification and quantification of the chiral forms of tartaric acid (TA), serving as a representative model system for materials exhibiting pronounced chiral characteristics. The proposed methodology relies on the principle of chirality, wherein the capacitance signal generated by the adsorption of D-TA and L-TA onto the surface of a platinum electrode (Pt-electrode) in an acidic solution is harnessed. The capacitance voltammograms were meticulously recorded under optimized experimental conditions. To compile the final dataset for the analyte, the average of the FFT capacitance voltammograms of the acidic solution (without the presence of the analyte) was subtracted from those containing the analyte. A distinct arrangement was obtained by employing PCA as a linear data transformation method, representing D-TA and L-TA in a two/three-dimensional space. The outcomes of the study reveal the successful detection of the two chiral forms of TA with a considerable degree of precision and reproducibility. Moreover, the proposed method facilitated the establishment of two linear response ranges for the concentration values of each enantiomer, spanning from 1 to 20 µM, and 50 to 500 µM. The respective detection limits were also determined to be 0.4 µM for L-TA and 1.3 µM for D-TA. These findings underscore the satisfactory sensitivity and efficiency of the proposed method in both qualitative and quantitative assessments of the chiral forms of TA.
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Affiliation(s)
- Mehrnaz Ebrahimi
- Chemistry Faculty, School of Sciences, University of Tehran, POB 14155-6455, Tehran, Iran
| | - Parviz Norouzi
- Chemistry Faculty, School of Sciences, University of Tehran, POB 14155-6455, Tehran, Iran.
- Laboratory of Advanced Biotechnologies for Health Assessments (Lab-HA), Lassonde School of Engineering, York University, Toronto, M3J 1P3, Canada.
- Department of Electrical Engineering and Computer Science, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
| | - Jahan B Ghasemi
- Chemistry Faculty, School of Sciences, University of Tehran, POB 14155-6455, Tehran, Iran
| | | | - Meissam Noroozifar
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada
| | - Razieh Salahandish
- Laboratory of Advanced Biotechnologies for Health Assessments (Lab-HA), Lassonde School of Engineering, York University, Toronto, M3J 1P3, Canada.
- Department of Electrical Engineering and Computer Science, York University, 4700 Keele Street, Toronto, ON, M3J 1P3, Canada.
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5
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Sonstrom RE, Vang ZP, Scolati HN, Neill JL, Pate BH, Clark JR. Rapid Enantiomeric Excess Measurements of Enantioisotopomers by Molecular Rotational Resonance Spectroscopy. Org Process Res Dev 2023; 27:1185-1197. [PMID: 38046274 PMCID: PMC10691865 DOI: 10.1021/acs.oprd.3c00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
Abstract
Recent work in drug discovery has shown that selectively deuterated small molecules can improve the safety and efficacy for active pharmaceutical ingredients. The advantages derive from changes in metabolism resulting from the kinetic isotope effect when deuterium is substituted for a hydrogen atom at a structural position where rate limiting C-H bond breaking occurs. This application has pushed the development of precision deuteration strategies in synthetic chemistry that can install deuterium atoms with high regioselectivity and with stereocontrol. Copper-catalyzed alkene transfer hydrodeuteration chemistry has recently been shown to have high stereoselectivity for deuteration at the metabolically important benzyl C-H position. In this case, stereocontrol results in the creation of enantioisotopomers-molecules that are chiral solely by virtue of the deuterium substitution-and chiral analysis techniques are needed to assess the reaction selectivity. It was recently shown that chiral tag molecular rotational resonance (MRR) spectroscopy provides a routine way to measure the enantiomeric excess and establish the absolute configuration of enantioisotopomers. High-throughput implementations of chiral tag MRR spectroscopy are needed to support optimization of the chemical synthesis. A measurement methodology for high-throughput chiral analysis is demonstrated in this work. The high-throughput ee measurements are performed using cavity-enhanced MRR spectroscopy, which reduces measurement times and sample consumption by more than an order-of-magnitude compared to the previous enantioisotopomer analysis using a broadband MRR spectrometer. It is also shown that transitions for monitoring the enantiomers can be selected from a broadband rotational spectrum without the need for spectroscopic analysis. The general applicability of chiral tag MRR spectroscopy is illustrated by performing chiral analysis on six enantioisotopomer reaction products using a single molecule as the tag for chiral discrimination.
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Affiliation(s)
| | - Zoua Pa Vang
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233-1881, United States
| | - Haley N Scolati
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, United States
| | - Justin L Neill
- BrightSpec Inc., Charlottesville, Virginia 22903, United States
| | - Brooks H Pate
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, United States
| | - Joseph R Clark
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233-1881, United States
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6
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Marshall MD, Leung HO. Molecular Structures and Microwave Spectra of the Gas-Phase Homodimers of 3-Fluoro-1,2-epoxypropane and 3,3-Difluoro-1,2-epoxypropane. J Phys Chem A 2023. [PMID: 37471074 DOI: 10.1021/acs.jpca.3c03643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Molecular structures for the heterochiral and homochiral gas-phase homodimers of 3-fluoro-1,2-epoxypropane and 3,3-difluoro-1,2-epoxypropane are investigated using both ab initio and density functional quantum chemistry calculations. Although microwave spectra for the heterochiral dimers are not observed as the lowest-energy isomers lack an electric dipole moment and others are presumably too high in energy, rotational spectra are observed for the homochiral dimers of each molecule that are consistent with the lowest-energy isomers of each. The presence of hydrogen atoms in the fluoromethyl groups makes it possible for these groups to participate in the intermolecular interactions that stabilize these dimers, resulting in a distinctly different bonding motif than is observed in the homodimers of 3,3,3-trifluoro-1,2-epoxypropane where the lack of a hydrogen atom prevents this possibility. The rotational spectra and energy ordering of the dimers are sufficiently well predicted with modest calculational methods to enable straightforward assignment of the observed spectra and to identify the molecular carrier of an assigned spectrum.
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Affiliation(s)
- Mark D Marshall
- Department of Chemistry, Amherst College, P.O. Box 5000, Amherst, Massachusetts 01002-5000, United States
| | - Helen O Leung
- Department of Chemistry, Amherst College, P.O. Box 5000, Amherst, Massachusetts 01002-5000, United States
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7
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Quesada-Moreno MM, Fatima M, Medel R, Pérez C, Schnell M. Sniffing out camphor: the fine balance between hydrogen bonding and London dispersion in the chirality recognition with α-fenchol. Phys Chem Chem Phys 2022; 24:12849-12859. [PMID: 35532923 DOI: 10.1039/d2cp00308b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Binary complexes between the chiral monoterpenoids camphor and α-fenchol were explored with vibrational and rotational jet spectroscopy as well as density functional theory in order to explore how chirality can influence the binding preferences in gas-phase complexes. The global minimum structures of the two diastereomers were assigned. It is found that chirality recognition leads to different compromises in the fine balance between intermolecular interactions. While one isomer features a stronger hydrogen bond, the other one is more tightly arranged and stabilized by larger London dispersion interactions. These new spectroscopic results help understand the influence of chirality in molecular aggregation and unveil the kind of interactions involved between a chiral alcohol and a chiral ketone with large dispersion contributions.
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Affiliation(s)
- María Mar Quesada-Moreno
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany. .,Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, 18071, Granada, Spain
| | - Mariyam Fatima
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany. .,I. Institute of Physics, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Robert Medel
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany.
| | - Cristóbal Pérez
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany. .,Departamento de Química Física y Química Inorgánica, Facultad de Ciencias & I.U. CINQUIMA, Universidad de Valladolid, E-47011 Valladolid, Spain
| | - Melanie Schnell
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany. .,Christian-Albrechts-Universität zu Kiel, Institut für Physikalische Chemie, Max-Eyth-Straße 1, 24118 Kiel, Germany.
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8
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Chiral Analysis of Linalool, an Important Natural Fragrance and Flavor Compound, by Molecular Rotational Resonance Spectroscopy. Symmetry (Basel) 2022. [DOI: 10.3390/sym14050917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
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 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.
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9
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Steber A, Li W, Pate BH, Lesarri A, Pérez C. The First Stages of Nanomicelle Formation Captured in the Sevoflurane Trimer. J Phys Chem Lett 2022; 13:3770-3775. [PMID: 35446045 PMCID: PMC9059180 DOI: 10.1021/acs.jpclett.2c00671] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 04/05/2022] [Indexed: 06/14/2023]
Abstract
Self-aggregation of sevoflurane, an inhalable, fluorinated anesthetic, provides a challenge for current state-of-the-art high-resolution techniques due to its large mass and the variety of possible hydrogen bonds between monomers. Here we present the observation of sevoflurane trimer by chirped-pulse Fourier transform microwave spectroscopy, identified through the interplay of experimental and computational methods. The trimer (>600 Da), one of the largest molecular aggregates observed through rotational spectroscopy, does not resemble the binding (C-H···O) motif of the already characterized sevoflurane dimer, instead adapting a new binding configuration created predominantly from 17 CH···F hydrogen bonds that resembles a nanomicellar arrangement. The observation of such a heavy aggregate highlights the potential of rotational spectroscopy to study larger biochemical systems in the limit of spectroscopic congestion but also showcases the challenges ahead as the mass of the system increases.
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Affiliation(s)
- Amanda
L. Steber
- Departamento
de Química Física y Química Inorgánica,
Facultad de Ciencias-I.U. CINQUIMA, Universidad
de Valladolid, E-47011 Valladolid, Spain
| | - Wenqin Li
- Departamento
de Química Física y Química Inorgánica,
Facultad de Ciencias-I.U. CINQUIMA, Universidad
de Valladolid, E-47011 Valladolid, Spain
| | - Brooks H. Pate
- Department
of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, United States
| | - Alberto Lesarri
- Departamento
de Química Física y Química Inorgánica,
Facultad de Ciencias-I.U. CINQUIMA, Universidad
de Valladolid, E-47011 Valladolid, Spain
| | - Cristóbal Pérez
- Departamento
de Química Física y Química Inorgánica,
Facultad de Ciencias-I.U. CINQUIMA, Universidad
de Valladolid, E-47011 Valladolid, Spain
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10
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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 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.
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11
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Construction and Demonstration of a 6–18 GHz Microwave Three-Wave Mixing Experiment Using Multiple Synchronized Arbitrary Waveform Generators. Symmetry (Basel) 2022. [DOI: 10.3390/sym14050848] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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 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.
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12
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Assignment-free chirality detection in unknown samples via microwave three-wave mixing. Commun Chem 2022; 5:31. [PMID: 36697786 PMCID: PMC9814651 DOI: 10.1038/s42004-022-00641-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 02/03/2022] [Indexed: 01/28/2023] Open
Abstract
Straightforward identification of chiral molecules in multi-component mixtures of unknown composition is extremely challenging. Current spectrometric and chromatographic methods cannot unambiguously identify components while the state of the art spectroscopic methods are limited by the difficult and time-consuming task of spectral assignment. Here, we introduce a highly sensitive generalized version of microwave three-wave mixing that uses broad-spectrum fields to detect chiral molecules in enantiomeric excess without any prior chemical knowledge of the sample. This method does not require spectral assignment as a necessary step to extract information out of a spectrum. We demonstrate our method by recording three-wave mixing spectra of multi-component samples that provide direct evidence of enantiomeric excess. Our method opens up new capabilities in ultrasensitive phase-coherent spectroscopic detection that can be applied for chiral detection in real-life mixtures, raw products of chemical reactions and difficult to assign novel exotic species.
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13
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Wang H, Chen J, Zheng Y, Obenchain DA, Xu X, Gou Q, Grabow JU, Caminati W. Interaction Types in C 6H 5(CH 2) nOH-CO 2 ( n = 0-4) Determined by the Length of the Side Alkyl Chain. J Phys Chem Lett 2022; 13:149-155. [PMID: 34962816 DOI: 10.1021/acs.jpclett.1c03740] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
C6H5(CH2)nOH-CO2 complexes have been investigated using rotational spectroscopy (n = 0-2) complemented by quantum chemical calculations (n = 0-4), which implies that the side alkyl chain length can determine the types of intermolecular interactions. Unlike the in-plane C···O tetrel bond in phenol-CO2, the π*CO2···πaromatic interaction has been shown to link CO2 to phenylmethanol and 2-phenylethanol, which is, to the best of our knowledge, the first time it has been demonstrated by rotational spectroscopy. Further elongations of the side alkyl chain gradually increase the energies of intramolecular hydrogen bonds in 3-phenylpropanol and 4-phenylbutanol so that CO2 cannot break it. CO2 will be pushed farther from the monomers and link with the -OH group through a dominating C···O tetrel bond. Our observations would allow, with the choice of the proper length of the side alkyl chain, new strategies for engineering C···πaromatic-centered noncovalent bonding schemes for the capture, utilization, and storage of CO2.
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Affiliation(s)
- Hao Wang
- Department of Chemistry, School of Chemistry and Chemical Engineering, Chongqing University, No. 55 Daxuecheng South Road, Shapingba, Chongqing 401331, China
| | - Junhua Chen
- Department of Chemistry, School of Chemistry and Chemical Engineering, Chongqing University, No. 55 Daxuecheng South Road, Shapingba, Chongqing 401331, China
| | - Yang Zheng
- Department of Chemistry, School of Chemistry and Chemical Engineering, Chongqing University, No. 55 Daxuecheng South Road, Shapingba, Chongqing 401331, China
| | - Daniel A Obenchain
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Xuefang Xu
- Department of Chemistry, School of Chemistry and Chemical Engineering, Chongqing University, No. 55 Daxuecheng South Road, Shapingba, Chongqing 401331, China
| | - Qian Gou
- Department of Chemistry, School of Chemistry and Chemical Engineering, Chongqing University, No. 55 Daxuecheng South Road, Shapingba, Chongqing 401331, China
| | - Jens-Uwe Grabow
- Institut für Physikalische Chemie & Elektrochemie, Leibniz Universität Hannover, Callinstraβe 3A, 30167 Hannover, Germany
| | - Walther Caminati
- Dipartimento di Chimica "G. Ciamician", Università di Bologna, Via Selmi 2, I-40126 Bologna, Italy
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14
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Gong L, Zhao Q, Wu S, Yin ZZ, Wu D, Cai W, Kong Y. Ultrasensitive Electrochemical Impedance Chiral Discrimination and Sensing of Tryptophan Isomers Based on Core-Shell-Structured Au-Ag Nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:14454-14462. [PMID: 34851110 DOI: 10.1021/acs.langmuir.1c02423] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Au-Ag nanoparticles (Au-Ag NPs) with a core-shell structure are prepared and used for ultrasensitive electrochemical impedance (EI) discrimination of the isomers of tryptophan (Trp). As revealed by circular dichroism, rotary polarization caused by the Au-Ag NPs is consistent with D-Trp but opposite to L-Trp, and thus, the Au-Ag NPs can selectively combine with D-Trp through preferential interactions. Compared with Au-Ag NPs, the composites of D-Trp and Au-Ag NPs (Au-Ag NPs/D-Trp) display significantly increased charge transfer resistance (Rct); differently, the Rct of Au-Ag NPs/L-Trp remains almost unchanged because the Au-Ag NPs exhibit poor affinity toward L-Trp. Therefore, ultrasensitive EI enantiodiscrimination of the isomers of Trp is realized even at an extremely low concentration of the Trp isomers (0.1 nM). In addition, it is successfully applied in the ultrasensitive determination of D-Trp at a low concentration level (0.1 nM∼10 μM).
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Affiliation(s)
- Ling Gong
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
- School of Chemical and Pharmaceutical Engineering, Changzhou Vocational Institute of Engineering, Changzhou 213164, China
| | - Qianqian Zhao
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Shanshan Wu
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Zheng-Zhi Yin
- College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing 314001, China
| | - Datong Wu
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Wenrong Cai
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Yong Kong
- Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
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15
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Sonstrom RE, Neill JL, Mikhonin AV, Doetzer R, Pate BH. Chiral analysis of pantolactone with molecular rotational resonance spectroscopy. Chirality 2021; 34:114-125. [PMID: 34698412 DOI: 10.1002/chir.23379] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 09/27/2021] [Accepted: 09/30/2021] [Indexed: 11/07/2022]
Abstract
A molecular rotational resonance spectroscopy method for measuring the enantiomeric excess of pantolactone, an intermediate in the synthesis of panthenol and pantothenic acid, is presented. The enantiomers are distinguished via complexation with a small chiral tag molecule, which produces diastereomeric complexes in the pulsed jet expansion used to inject the sample into the spectrometer. These complexes have distinct moments of inertia, so their spectra are resolved by MRR spectroscopy. Quantitative enantiomeric excess (EE) measurements are made by taking the ratio of normalized complex signal levels when a chiral tag sample of high, known EE is used, while the absolute configuration of the sample can be determined from electronic structure calculations of the complex geometries. These measurements can be performed without the need for reference samples with known enantiopurity. Two instruments were used in the analysis. A broadband, chirped-pulse spectrometer is used to perform structural characterization of the complexes. The broadband spectrometer is also used to determine the EE; however, this approach requires relatively long measurement times. A targeted MRR spectrometer is also used to demonstrate EE analysis with approximately 15-min sample-to-sample cycle time. The quantitative accuracy of the method is demonstrated by comparison with chiral gas chromatography and through the measurement of a series of reference samples prepared from mixtures of (R)-pantolactone and (S)-pantolactone samples of known EE.
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Affiliation(s)
- Reilly E Sonstrom
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
- BrightSpec, Inc., Charlottesville, Virginia, USA
| | | | | | | | - Brooks H Pate
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
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16
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Dindić C, Nguyen HVL. Microwave Spectrum of Two-Top Molecule: 2-Acetyl-3-Methylthiophene. Chemphyschem 2021; 22:2420-2428. [PMID: 34546633 DOI: 10.1002/cphc.202100514] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 08/19/2021] [Indexed: 11/06/2022]
Abstract
The microwave spectrum of 2-acetyl-3-methylthiophene (2A3MT) was recorded in the frequency range from 2 to 26.5 GHz using a molecular jet Fourier transform microwave spectrometer and could be fully assigned to the anti-conformer of the molecule, while the syn-conformer was not observable. Torsional splittings of all rotational transitions in quintets due to internal rotations of the acetyl methyl and the ring methyl groups were resolved and analyzed, yielding barriers to internal rotation of 306.184(46) cm-1 and 321.813(64) cm-1 , respectively. The rotational and centrifugal distortion constants were determined with high accuracy, and the experimental values are compared to those derived from quantum chemical calculations. The experimentally determined inertial defect supports the conclusion that anti-2A3MT is planar, even though a number of MP2 calculations predicted the contrary.
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Affiliation(s)
- Christina Dindić
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Ha Vinh Lam Nguyen
- Univ Paris Est Creteil and Université de Paris, CNRS, LISA, 94010, Créteil, France.,Institut Universitaire de France (IUF), 75231, Paris cedex 05, France
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17
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Chen J, Wang H, Kisiel Z, Gou Q, Caminati W. Hydrogen versus tetrel bonds in complexes of 3-oxetanone with water and formaldehyde. Phys Chem Chem Phys 2021; 23:7295-7301. [PMID: 33876089 DOI: 10.1039/d1cp00239b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ability and preference of 3-oxetanone to form hydrogen or tetrel bonds have been investigated in its complexes with water and formaldehyde by using Fourier transform microwave spectroscopy complemented with quantum chemical calculations. Different types of interactions and internal dynamics have been observed in the targeted complexes. With water, the ether oxygen of 3-oxetanone is the favoured interaction site forming a classical O-HO hydrogen bond. Quite differently, the carbonyl group of 3-oxetanone plays the dual role as a tetrel donor and a proton acceptor in the 3-oxetanone-formaldehyde complex, featuring the CO tetrel bond and C-HO weak hydrogen bond interactions. Splittings originated from the internal rotation of formaldehyde around its C2 axis were also observed. The V2 barrier was estimated to be 375(10) cm-1 based on Meyer's one-dimensional flexible model. The changes in geometries and electronic densities upon complexation would shed light on the impact of archetype solvent and organic substrate molecules on the reactivity of 3-oxetanone.
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Affiliation(s)
- Junhua Chen
- School of Chemistry and Chemical Engineering, Chongqing University, No. 55 Daxuecheng South Rd, Shapingba, Chongqing 401331, China.
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18
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Xie F, Seifert NA, Hazrah AS, Jäger W, Xu Y. Conformational Landscape, Chirality Recognition and Chiral Analyses: Rotational Spectroscopy of Tetrahydro-2-Furoic Acid⋅⋅⋅Propylene Oxide Conformers. Chemphyschem 2021; 22:455-460. [PMID: 33453085 DOI: 10.1002/cphc.202000995] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 12/31/2020] [Indexed: 11/05/2022]
Abstract
A chiral adduct formed between a chiral carboxylic acid, tetrahydro-2-furoic acid (THFA), and a chiral ester, propylene oxide (PO), was investigated using rotational spectroscopy and DFT calculations. Isolated THFA exists dominantly as three different conformers: I, II, and III in a jet, with I and II taking on the trans-COOH configuration and III having the cis-COOH configuration. We utilized CREST, a conformational ensemble space exploration tool, to identify the possible conformations of the binary adduct, THFA⋅⋅⋅PO. Subsequent DFT geometry optimizations predicted about two hundred homochiral and heterochiral binary structures with 28 low energy structures within an energy window of 15 kJ mol-1 . A rich broadband rotational spectrum was obtained with a mixture of trace amounts of THFA+PO in neon in a supersonic jet expansion. Six THFA⋅⋅⋅PO conformers were identified experimentally. Kinetically favored binary products which contain trans-COOH I dominate among the observed conformers, while thermodynamically more stable adducts were also detected. Detailed analyses of the structures of the observed conformers show interesting chirality-controlled structural preferences. Such non-covalently bound chiral contact pairs are the foundation of chiral-tag rotational spectroscopy, an exciting new analytical application of rotational spectroscopy for determination of enantiomeric excess. Enantiomeric excess analyses were performed and the results are discussed.
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Affiliation(s)
- Fan Xie
- Department of Chemistry, University of Alberta Edmonton, Alberta, T6G 2G2, Canada
| | - Nathan A Seifert
- Current address: Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Arsh S Hazrah
- Department of Chemistry, University of Alberta Edmonton, Alberta, T6G 2G2, Canada
| | - Wolfgang Jäger
- Department of Chemistry, University of Alberta Edmonton, Alberta, T6G 2G2, Canada
| | - Yunjie Xu
- Department of Chemistry, University of Alberta Edmonton, Alberta, T6G 2G2, Canada
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19
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Juanes M, Saragi RT, Enríquez L, Jaraíz M, Lesarri A. Molecular Rotation Spectrum of Tetracyclic Quinolizidines: Observation of trans-Matrine and the Elusive cis-Matrine. J Org Chem 2021; 86:1861-1867. [PMID: 33405924 DOI: 10.1021/acs.joc.0c02689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We characterized the bis-quinolizidine tetracyclic alkaloid (5S, 6S, 7R, 11R)-matrine in a supersonic jet expansion, using chirped-pulsed broadband microwave spectroscopy. Previous crystal diffraction analyses suggested 16 diastereoisomers associated with matrine's four carbon stereocenters but were inconclusive whether the lactamic nitrogen atom would additionally produce separated trans-/cis- diastereoisomers or if both species may interconvert through low potential barriers. Our experiment simultaneously detected trans- and cis-matrine through their rotational spectrum, confirming the possibility of conformational rearrangement in matrine alkaloids. The two matrine conformers mainly differ in the envelope or half-chair lactamic ring, as evidenced by the experimental rotational and nuclear quadrupole coupling parameters. Molecular orbital calculations with ab initio (MP2) and density functional methods (B3LYP-D3(BJ) and MN15) were tested against the experiment, additionally offering an estimation of the cis-/trans- barrier of 24.9-26.9 kJ mol-1. The experiment illustrates the structural potential of chirped-pulsed broadband microwave spectroscopy for high-resolution rotational studies of biomolecules in the range of 20-40 atoms.
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Affiliation(s)
- Marcos Juanes
- Departamento de Química Física y Química Inorgánica, Facultad de Ciencias-I.U. CINQUIMA, Universidad de Valladolid, Paseo de Belén, 7, 47011 Valladolid, Spain
| | - Rizalina Tama Saragi
- Departamento de Química Física y Química Inorgánica, Facultad de Ciencias-I.U. CINQUIMA, Universidad de Valladolid, Paseo de Belén, 7, 47011 Valladolid, Spain
| | - Lourdes Enríquez
- Departamento de Electrónica, ETSIT, Universidad de Valladolid, Paseo de Belén, 11, 47011 Valladolid, Spain
| | - Martín Jaraíz
- Departamento de Electrónica, ETSIT, Universidad de Valladolid, Paseo de Belén, 11, 47011 Valladolid, Spain
| | - Alberto Lesarri
- Departamento de Química Física y Química Inorgánica, Facultad de Ciencias-I.U. CINQUIMA, Universidad de Valladolid, Paseo de Belén, 7, 47011 Valladolid, Spain
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