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Puente AR, Polavarapu PL. Influence of microsolvation on vibrational circular dichroism spectra in dimethyl sulfoxide solvent: A Bottom-Up approach using Quantum cluster growth. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 303:123231. [PMID: 37562213 DOI: 10.1016/j.saa.2023.123231] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 07/09/2023] [Accepted: 08/01/2023] [Indexed: 08/12/2023]
Abstract
Chiroptical spectroscopic measurements serve as routine methods to assign the absolute configuration of chiral compounds and interpret their conformational behavior in solution. One common challenge is the use of strongly hydrogen-bonding solvents, which can significantly bias the conformational ensemble and affect the vibrational circular dichroism (VCD) active bands in solution. One such solvent is dimethyl sulfoxide (DMSO)-an excellent solvent for stubborn compounds-that must be explicitly considered in VCD analysis. Explicit consideration of solvent remains a critical challenge in chiroptical spectroscopy due to the need to explore solute-solvent conformational space and the computational expense in modeling these clusters. Interested in the recent development of the Quantum Cluster Growth (QCG) program by the Grimme lab, we set out to model and interpret previously reported VCD spectra for several molecules using their efficient program. Our purposes are two-fold: (1) to investigate the applicability of the QCG program to the problem of reproducing VCD spectra in DMSO solvent and (2) to identify limitations in using this approach. We find that we can conveniently model and analyze the VCD spectra of investigated molecules in DMSO. However, the final set of conformers used for VCD calculations are functional dependent and different sets of conformers can provide satisfactory quantitative agreement between experimental and predicted VCD spectra. We hope that this study provides guidance for future chiroptical studies in the challenging DMSO solvent.
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Affiliation(s)
- Andrew R Puente
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
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Merten C. Modelling solute-solvent interactions in VCD spectra analysis with the micro-solvation approach. Phys Chem Chem Phys 2023; 25:29404-29414. [PMID: 37881890 DOI: 10.1039/d3cp03408a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2023]
Abstract
Vibrational circular dichroism (VCD) spectroscopy has become an important part of the (stereo-)chemists' toolbox as a reliable method for the determination of absolute configurations. Being the chiroptical version of infrared spectroscopy, it has also been recognized as being very sensitive to conformational changes and intermolecular interactions. This sensitivity originates from the fact that the VCD spectra of individual conformers are often more different than their IR spectra, so that changes in conformational distributions or band positions and intensities become more pronounced. What is an advantage for studies focussing on intermolecular interactions can, however, quickly turn into a major obstacle during AC determinations: solute-solvent interactions can have a strong influence on spectral signatures and they must be accurately treated when simulating VCD and IR spectra. In this perspective, we showcase selected examples which exhibit particularly pronounced solvent effects. It is demonstrated that it is typically sufficient to model solute-solvent interactions by placing single solvent molecules near hydrogen bonding sites of the solute and subsequently use the optimized structures for spectra simulations. This micro-solvation approach works reasonably well for medium-sized, not too conformationally flexible molecules. We thus also discuss its limitations and outline the next steps that method development needs to take in order to further improve the workflows for VCD spectra predictions.
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Affiliation(s)
- Christian Merten
- Ruhr Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraße 150, 44801 Bochum, Germany.
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Le Barbu-Debus K, Zehnacker A. Competition between inter and intramolecular hydrogen bond evidenced by vibrational circular dichroism spectroscopy: The case of (1S,2R)-(-)-cis-1-amino-2-indanol. Chirality 2021; 33:858-874. [PMID: 34570370 DOI: 10.1002/chir.23362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 08/29/2021] [Accepted: 08/31/2021] [Indexed: 02/06/2023]
Abstract
The infrared (IR) absorption and vibrational circular dichroism (VCD) spectra of an intramolecularly hydrogen-bonded chiral amino-alcohol, (1S,2R)-(-)-cis-1-amino-2-indanol, are studied in DMSO-d6 . The spectra are simulated at the density functional theory (DFT) level within the frame of the cluster-in-the-liquid model. Both IR and VCD spectra show a clear signature of the formation of intermolecular hydrogen bonds at the detriment of the intramolecular OH … N interaction present in the isolated molecule. Two solvent molecules are necessary to reproduce the experimental spectra. Whereas the first DMSO molecule captures the main spectral modifications due to hydrogen bond formation between the solute and the solvent, the second DMSO molecule is necessary for a good description of the Boltzmann contribution of the different complexes, based on their Gibbs free energy.
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Affiliation(s)
- Katia Le Barbu-Debus
- Institut des Sciences Moléculaires d'Orsay, Université Paris-Saclay, Orsay, France
| | - Anne Zehnacker
- Institut des Sciences Moléculaires d'Orsay, Université Paris-Saclay, Orsay, France
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Koenis MAJ, Nicu VP, Visscher L, Kuehn C, Bremer M, Krier M, Untenecker H, Zhumaev U, Küstner B, Buma WJ. Vibrational circular dichroism studies of exceptionally strong chirality inducers in liquid crystals. Phys Chem Chem Phys 2021; 23:10021-10028. [DOI: 10.1039/d1cp00854d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Chiral dopants are used in liquid crystal displays to introduce uniform helical alignment. VCD can provide unambiguous determination of the absolute configuration and structural details of such a dopant, while X-ray crystallography fails.
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Koenis MAJ, Visser O, Visscher L, Buma WJ, Nicu VP. GUI Implementation of VCDtools, A Program to Analyze Computed Vibrational Circular Dichroism Spectra. J Chem Inf Model 2020; 60:259-267. [PMID: 31830414 PMCID: PMC6988127 DOI: 10.1021/acs.jcim.9b00956] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
As
computing power increases, vibrational circular dichroism (VCD)
calculations on molecules of larger sizes and complexities become
possible. At the same time, the spectra resulting from these computations
become increasingly more cumbersome to analyze. Here, we describe
the GUI implementation into the Amsterdam Density Functional (ADF)
software package of VCDtools, a toolbox that provides a user-friendly
means to analyze VCD spectra. Key features are the use of the generalized
coupled oscillator analysis methods, as well as an easy visualization
of the atomic electric and magnetic transition dipole moments which
together provide detailed insight in the origin of the VCD intensity.
Using several prototypical examples we demonstrate the functionalities
of the program. In particular, we show how the spectra can be analyzed
to detect differences between theory and experiment arising from large-amplitude
motions or incorrect molecular structures and, most importantly, how
the program can be used to prevent incorrect enantiomeric assignments.
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Affiliation(s)
- Mark A J Koenis
- Van 't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098 XH Amsterdam , The Netherlands
| | - Olivier Visser
- Software for Chemisty and Materials , De Boelelaan 1083 , 1081 HV Amsterdam , The Netherlands
| | - Lucas Visscher
- Amsterdam Center for Multiscale Modeling, Section Theoretical Chemistry, Faculty of Sciences , Vrije Universiteit Amsterdam , De Boelelaan 1083 , 1081 HV Amsterdam , The Netherlands
| | - Wybren J Buma
- Van 't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098 XH Amsterdam , The Netherlands.,Institute for Molecules and Materials, FELIX Laboratory , Radboud University , Toernooiveld 7c , 6525 ED Nijmegen , The Netherlands
| | - Valentin P Nicu
- Department of Environmental Science, Physics, Physical Education and Sport , Lucian Blaga University of Sibiu , loan Ratiu Street, Number 7-9 , 550012 Sibiu , Romania
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Koenis MAJ, Xia Y, Domingos SR, Visscher L, Buma WJ, Nicu VP. Taming conformational heterogeneity in and with vibrational circular dichroism spectroscopy. Chem Sci 2019; 10:7680-7689. [PMID: 31803406 PMCID: PMC6844231 DOI: 10.1039/c9sc02866h] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 07/08/2019] [Indexed: 01/19/2023] Open
Abstract
Genetic fitting algorithm accounting for the uncertainty in computed energies allows a significantly more reliable assignment of stereochemistry and conformational heterogeneity of chiral compounds using vibrational circular dichroism.
The flexibility of a molecule has important consequences on its function and application. Vibrational Circular Dichroism (VCD) is intrinsically an excellent experimental technique to get a hold on this flexibility as it is highly sensitive to key conformational details and able to distinguish rapidly interconverting conformers. One of the major challenges in analyzing the spectra by comparison to theoretical predictions is the uncertainty in the computed energies of the multitude of conformations. This uncertainty also affects the reliability of the stereochemical assignment it is normally used for. We present here a novel approach that explicitly takes the energy uncertainties into account in a genetic algorithm based method that fits calculated to the experimental spectra. We show that this approach leads to significant improvements over previously used methodologies. Importantly, statistical validation studies provide quantitative measures for the reliability of relevant parameters used such as the energy uncertainty and the extent to which conformational heterogeneity can be determined. Similarly, quantitative measures can be obtained for the possibility that the flexibility that is introduced in the fit might lead to an incorrect assignment of the stereochemistry. These results break new ground for different techniques based on VCD to elucidate conformational flexibility.
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Affiliation(s)
- Mark A J Koenis
- Van't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098 XH Amsterdam , The Netherlands .
| | - Yiyin Xia
- Van't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098 XH Amsterdam , The Netherlands .
| | - Sérgio R Domingos
- Deutsches Elektronen-Synchrotron DESY , Notkestraße 85 , 22607 Hamburg , Germany
| | - Lucas Visscher
- Amsterdam Center for Multiscale Modeling , Division Theoretical Chemistry , Faculty of Sciences , Vrije Universiteit Amsterdam , De Boelelaan 1083 , 1081 HV Amsterdam , The Netherlands
| | - Wybren Jan Buma
- Van't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , 1098 XH Amsterdam , The Netherlands . .,Radboud University , Institute for Molecules and Materials , FELIX Laboratory , Toernooiveld 7c , 6525 ED Nijmegen , The Netherlands
| | - Valentin P Nicu
- Department of Environmental Science, Physics, Physical Education and Sport , Lucian Blaga University of Sibiu , loan Ratiu Street Nr. 7-9 , 550012 Sibiu , Romania .
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Johnson J, Polavarapu PL. Chiral Molecular Structures of Substituted Indans: Ring Puckering, Rotatable Substituents, and Vibrational Circular Dichroism. ACS OMEGA 2019; 4:4963-4976. [PMID: 31459680 PMCID: PMC6648482 DOI: 10.1021/acsomega.8b03628] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Accepted: 02/21/2019] [Indexed: 05/06/2023]
Abstract
The chiral molecular structures of four different substituted indans, namely, (S)-1-methylindan, (R)-1-methylindan-1-d, (R)-1-aminoindan, and (S)-1-indanol, were investigated using experimental vibrational absorption and vibrational circular dichroism spectra and corresponding spectra predicted using quantum chemical (QC) calculations. All of these molecules possess two ring puckering conformations, with ring puckering leading to the pseudoequatorial substituent being approximately four times more abundant over that leading to the pseudoaxial substituent. The amino group in 1-aminoindan has three conformations arising from the rotation of NH2 group, for each ring puckering conformation, resulting in a total of six conformations. Whereas 1-indanol in the nonhydrogen-bonding solvent CCl4 also has six conformations similar to those of 1-aminoindan, 1-indanol in the hydrogen-bonding solvent DMSO-d 6 adopts numerous conformations, of which 30 conformers are considered to have at least ∼1% or more population. In DMSO solution, ring puckering leading to pseudoequatorial substituent accounts for 77% population and 23% for pseudoaxial substituent. The QC spectra predicted for the geometry optimized conformers are found to be in excellent quantitative agreement with corresponding experimental spectra in all of the molecules considered. The procedures suggested in this work are hoped to provide successful pathways for future chiral molecular structural analyses.
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Weirich L, Merten C. Solvation and self-aggregation of chiral alcohols: how hydrogen bonding affects their VCD spectral signatures. Phys Chem Chem Phys 2019; 21:13494-13503. [DOI: 10.1039/c9cp01407a] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
IR and VCD spectra of chiral alcohols in different solvents are analyzed with DFT spectra calculations. We show that for ACN or DMSO explicit solvation is needed to reproduce experimental spectra.
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Affiliation(s)
- Luisa Weirich
- Ruhr-Universität Bochum
- Fakultät für Chemie und Biochemie
- Organische Chemie II
- 44801 Bochum
- Germany
| | - Christian Merten
- Ruhr-Universität Bochum
- Fakultät für Chemie und Biochemie
- Organische Chemie II
- 44801 Bochum
- Germany
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