1
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Salvino RA, De Luca G, Celebre G. Assessing the chirality-dependent conformational distribution of small flexible opposite enantiomers dissolved in weakly ordering enantiopure media by means of liquid crystal NMR techniques. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.117994] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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2
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Aroulanda C, Lesot P. Molecular enantiodiscrimination by NMR spectroscopy in chiral oriented systems: Concept, tools, and applications. Chirality 2021; 34:182-244. [PMID: 34936130 DOI: 10.1002/chir.23386] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 09/20/2021] [Accepted: 10/15/2021] [Indexed: 11/06/2022]
Abstract
The study of enantiodiscriminations in relation to various facets of enantiomorphism (chirality/prochirality) and/or molecular symmetry is an exciting area of modern organic chemistry and an ongoing challenge for nuclear magnetic resonance (NMR) spectroscopists who have developed many useful analytical approaches to solve stereochemical problems. Among them, the anisotropic NMR using chiral aligning solvents has provided a set of new and original tools by making accessible all intramolecular, order-dependent NMR interactions (anisotropic interactions), such as residual chemical shift anisotropy (RCSA), residual dipolar coupling (RDC), and residual quadrupolar coupling (RQC) for spin I > 1/2, while preserving high spectral resolution. The force of NMR in enantiopure, oriented solvents lies on its ability to orient differently in average on the NMR timescale enantiomers of chiral molecules and enantiotopic elements of prochiral ones, leading distinct NMR spectra or signals to be detected. In this compendium mainly written for all chemists playing with (pro)chirality, we overview various key aspects of NMR in weakly aligning chiral solvents as the lyotropic liquid crystals (LLCs), in particular those developed in France to study (pro)chiral compounds in relation with chemists needs: study of enantiopurity of mixture, stereochemistry, natural isotopic fractionation, as well as molecular conformation and configuration. Key representative examples covering the diversity of enantiomorphism concept, and the main and most recent applications illustrating the analytical potential of this NMR in polypeptide-based chiral liquid crystals (CLCs) are examined. The latest analytical strategy developed to determine in-solution conformational distribution of flexibles solutes using NMR in polypeptide-based aligned solvents is also proposed.
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Affiliation(s)
- Christie Aroulanda
- RMN en Milieu Orienté, ICMMO, UMR CNRS 8182, Université Paris-Saclay, Orsay cedex, France
| | - Philippe Lesot
- RMN en Milieu Orienté, ICMMO, UMR CNRS 8182, Université Paris-Saclay, Orsay cedex, France
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3
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Sager E, Tzvetkova P, Gossert AD, Piechon P, Luy B. Determination of Configuration and Conformation of a Reserpine Derivative with Seven Stereogenic Centers Using Molecular Dynamics with RDC-Derived Tensorial Constraints*. Chemistry 2020; 26:14435-14444. [PMID: 32744785 PMCID: PMC7702126 DOI: 10.1002/chem.202002642] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 07/22/2020] [Indexed: 11/11/2022]
Abstract
NMR-based determination of the configuration of complex molecules containing many stereocenters is often not possible using traditional NOE data and coupling patterns. Making use of residual dipolar couplings (RDCs), we were able to determine the relative configuration of a natural product containing seven stereocenters, including a chiral amine lacking direct RDC data. To identify the correct relative configuration out of 32 possible ones, experimental RDCs were used in three different approaches for data interpretation: by fitting experimental data based singular value decomposition (SVD) using a single alignment tensor and either (i) a single conformer or (ii) multiple conformers, or alternatively (iii) using molecular dynamics simulations with tensorial orientational constraints (MDOC). Even though in all three approaches one and the same configuration could be selected and clear discrimination between possible configurations was achieved, the experimental data was not fully satisfied by the methods based on single tensor approaches. While these two approaches are faster, only MDOC is able to fully reproduce experimental results, as the obtained conformational ensemble adequately covers the conformational space necessary to describe the molecule with inherent flexibility.
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Affiliation(s)
- Emine Sager
- Institut für Organische ChemieKarlsruher Institut für Technologie (KIT)Fritz-Haber-Weg 676131KarlsruheGermany
- Novartis Pharma AGNovartis Institutes for Biomedical Research4002BaselSwitzerland
| | - Pavleta Tzvetkova
- Institut für Biologische Grenzflächen 4—Magnetische ResonanzKarlsruher Institut für Technologie (KIT)Postfach 364076021KarlsruheGermany
| | - Alvar D. Gossert
- Novartis Pharma AGNovartis Institutes for Biomedical Research4002BaselSwitzerland
- Institut für Molekularbiologie und BiophysikETH Zürich8093ZürichSwitzerland
| | - Philippe Piechon
- Novartis Pharma AGNovartis Institutes for Biomedical Research4002BaselSwitzerland
| | - Burkhard Luy
- Institut für Organische ChemieKarlsruher Institut für Technologie (KIT)Fritz-Haber-Weg 676131KarlsruheGermany
- Institut für Biologische Grenzflächen 4—Magnetische ResonanzKarlsruher Institut für Technologie (KIT)Postfach 364076021KarlsruheGermany
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4
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Lesot P, Aroulanda C, Berdagué P, Meddour A, Merlet D, Farjon J, Giraud N, Lafon O. Multinuclear NMR in polypeptide liquid crystals: Three fertile decades of methodological developments and analytical challenges. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2020; 116:85-154. [PMID: 32130960 DOI: 10.1016/j.pnmrs.2019.10.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 10/24/2019] [Indexed: 06/10/2023]
Abstract
NMR spectroscopy of oriented samples makes accessible residual anisotropic intramolecular NMR interactions, such as chemical shift anisotropy (RCSA), dipolar coupling (RDC), and quadrupolar coupling (RQC), while preserving high spectral resolution. In addition, in a chiral aligned environment, enantiomers of chiral molecules or enantiopic elements of prochiral compounds adopt different average orientations on the NMR timescale, and hence produce distinct NMR spectra or signals. NMR spectroscopy in chiral aligned media is a powerful analytical tool, and notably provides unique information on (pro)chirality analysis, natural isotopic fractionation, stereochemistry, as well as molecular conformation and configuration. Significant progress has been made in this area over the three last decades, particularly using polypeptide-based chiral liquid crystals (CLCs) made of organic solutions of helically chiral polymers (as PBLG) in organic solvents. This review presents an overview of NMR in polymeric LCs. In particular, we describe the theoretical tools and the major NMR methods that have been developed and applied to study (pro)chiral molecules dissolved in such oriented solvents. We also discuss the representative applications illustrating the analytical potential of this original NMR tool. This overview article is dedicated to thirty years of original contributions to the development of NMR spectroscopy in polypeptide-based chiral liquid crystals.
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Affiliation(s)
- Philippe Lesot
- Université Paris Sud/Université Paris-Saclay, UMR CNRS 8182, Institut de Chimie Moléculaire et des Matériaux d'Orsay, ICMMO, Equipe RMN en Milieu Orienté, Bât. 410, 15 rue du Doyen Georges Poitou, F-91405 Orsay cedex, France; Centre National de la Recherche Scientifique (CNRS), France.
| | - Christie Aroulanda
- Université Paris Sud/Université Paris-Saclay, UMR CNRS 8182, Institut de Chimie Moléculaire et des Matériaux d'Orsay, ICMMO, Equipe RMN en Milieu Orienté, Bât. 410, 15 rue du Doyen Georges Poitou, F-91405 Orsay cedex, France
| | - Philippe Berdagué
- Université Paris Sud/Université Paris-Saclay, UMR CNRS 8182, Institut de Chimie Moléculaire et des Matériaux d'Orsay, ICMMO, Equipe RMN en Milieu Orienté, Bât. 410, 15 rue du Doyen Georges Poitou, F-91405 Orsay cedex, France
| | - Abdelkrim Meddour
- Université Paris Sud/Université Paris-Saclay, UMR CNRS 8182, Institut de Chimie Moléculaire et des Matériaux d'Orsay, ICMMO, Equipe RMN en Milieu Orienté, Bât. 410, 15 rue du Doyen Georges Poitou, F-91405 Orsay cedex, France
| | - Denis Merlet
- Université Paris Sud/Université Paris-Saclay, UMR CNRS 8182, Institut de Chimie Moléculaire et des Matériaux d'Orsay, ICMMO, Equipe RMN en Milieu Orienté, Bât. 410, 15 rue du Doyen Georges Poitou, F-91405 Orsay cedex, France
| | - Jonathan Farjon
- Centre National de la Recherche Scientifique (CNRS), France; Faculté des Sciences et Techniques de Nantes, UMR CNRS 6230, Chimie et Interdisciplinarité, Synthèse, Analyse, Modélisation, CEISAM, Equipe EBSI, BP 92208, 2 rue de la Houssinière, F-44322 Nantes cedex 3, France
| | - Nicolas Giraud
- Université Paris Descartes, Sorbonne Paris Cité, UMR CNRS 8601, Laboratory of Pharmacological and Toxicological Chemistry and Biochemistry, LPTCB, 45 rue des Saints Pères, F-75006 Paris, France
| | - Olivier Lafon
- Universite de Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR CNRS 8181, Unité de Catalyse et Chimie du Solide, UCCS, F-59000 Lille, France; Institut Universitaire de France (IUF), France
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5
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Tzvetkova P, Sternberg U, Gloge T, Navarro-Vázquez A, Luy B. Configuration determination by residual dipolar couplings: accessing the full conformational space by molecular dynamics with tensorial constraints. Chem Sci 2019; 10:8774-8791. [PMID: 31803450 PMCID: PMC6849632 DOI: 10.1039/c9sc01084j] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 07/19/2019] [Indexed: 12/27/2022] Open
Abstract
Residual dipolar couplings (RDCs) and other residual anisotropic NMR parameters provide valuable structural information of high quality and quantity, bringing detailed structural models of flexible molecules in solution in reach. The corresponding data interpretation so far is directly or indirectly based on the concept of a molecular alignment tensor, which, however, is ill-defined for flexible molecules. The concept is typically applied to a single or a small set of lowest energy structures, ignoring the effect of vibrational averaging. Here, we introduce an entirely different approach based on time averaged molecular dynamics with dipolar couplings as tensorial orientational restraints that can be used to solve structural problems in molecules of any size without the need of introducing an explicit molecular alignment tensor into the computation. RDC restraints are represented by their full 3D interaction tensor in the laboratory frame, for which pseudo forces are calculated using a secular dipolar Hamiltonian as the target. The resulting rotational averaging of each individual tensorial restraint leads to structural ensembles that best fulfil the experimental data. Using one-bond RDCs, the approach has been implemented in the force field procedures of the program COSMOS and extensively tested. A concise theoretical introduction, including the special treatment of force fields for stable and fast MD simulations, as well as applications regarding configurational analyses of small to medium-sized organic molecules with different degrees of flexibility, is given. The observed results are discussed in detail.
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Affiliation(s)
- Pavleta Tzvetkova
- Institute of Organic Chemistry and Institute for Biological Interfaces 4 - Magnetic Resonance , Karlsruhe Institute of Technology (KIT) , Fritz-Haber-Weg 6 , 76131 Karlsruhe , Germany . ;
| | - Ulrich Sternberg
- Institute of Organic Chemistry and Institute for Biological Interfaces 4 - Magnetic Resonance , Karlsruhe Institute of Technology (KIT) , Fritz-Haber-Weg 6 , 76131 Karlsruhe , Germany . ;
| | - Thomas Gloge
- Institute of Organic Chemistry and Institute for Biological Interfaces 4 - Magnetic Resonance , Karlsruhe Institute of Technology (KIT) , Fritz-Haber-Weg 6 , 76131 Karlsruhe , Germany . ;
| | - Armando Navarro-Vázquez
- Institute of Organic Chemistry and Institute for Biological Interfaces 4 - Magnetic Resonance , Karlsruhe Institute of Technology (KIT) , Fritz-Haber-Weg 6 , 76131 Karlsruhe , Germany . ;
| | - Burkhard Luy
- Institute of Organic Chemistry and Institute for Biological Interfaces 4 - Magnetic Resonance , Karlsruhe Institute of Technology (KIT) , Fritz-Haber-Weg 6 , 76131 Karlsruhe , Germany . ;
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6
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Di Pietro ME, Sternberg U, Luy B. Molecular Dynamics with Orientational Tensorial Constraints: A New Approach to Probe the Torsional Angle Distributions of Small Rotationally Flexible Molecules. J Phys Chem B 2019; 123:8480-8491. [PMID: 31502838 DOI: 10.1021/acs.jpcb.9b07008] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The potential of residual dipolar couplings (RDCs) in conformational studies of small molecules is now widely recognized, but current theoretical approaches for their interpretation have several limitations and there is still the need for a general method to probe the torsional angle distributions applicable to any rotationally flexible molecule. Molecular dynamics simulations with RDC-based orientational tensorial constraints (MDOC), implemented in the software COSMOS, are presented here as a conceptually new strategy. For the cases of the fluorinated anti-inflammatory drug diflunisal and the disaccharide cellobiose, we demonstrate that MDOC simulations with one-bond RDCs as tensorial constraints unveil torsion distributions and allow the determination of relative configuration in the presence of rotational flexibility. The independence of the initial structure or any a priori assumption as well as the possibility to combine different experimental constraints represent features, which make the COSMOS software a promising tool for the investigation of torsional angle distributions of flexible molecules, regardless of their size and degree of freedom.
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Affiliation(s)
- Maria E Di Pietro
- Institute of Organic Chemistry , Karlsruhe Institute of Technology (KIT) , Karlsruhe 76131 , Germany
| | - Ulrich Sternberg
- COSMOS GbR , Jena 07743 , Germany.,Research Partner , Karlsruhe Institute of Technology (KIT) , Karlsruhe 76131 , Germany
| | - Burkhard Luy
- Institute of Organic Chemistry , Karlsruhe Institute of Technology (KIT) , Karlsruhe 76131 , Germany.,Institute for Biological Interfaces 4-Magnetic Resonance , Karlsruhe Institute of Technology (KIT) , Eggenstein-Leopoldshafen 76021 , Germany
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7
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Di Pietro ME, Celebre G, Aroulanda C, Merlet D, De Luca G. Assessing the stable conformations of ibuprofen in solution by means of Residual Dipolar Couplings. Eur J Pharm Sci 2017; 106:113-121. [DOI: 10.1016/j.ejps.2017.05.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Revised: 04/21/2017] [Accepted: 05/13/2017] [Indexed: 11/28/2022]
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8
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Di Pietro ME, Aroulanda C, Celebre G, Merlet D, De Luca G. The conformational behaviour of naproxen and flurbiprofen in solution by NMR spectroscopy. NEW J CHEM 2015. [DOI: 10.1039/c5nj01753j] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The conformational equilibrium of common anti-inflammatory drugs has been studied experimentally in solution by NMR in weakly ordered PBLG phases.
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Affiliation(s)
- Maria Enrica Di Pietro
- Lab. LXNMR_S.C.An
- Dipartimento di Chimica e Tecnologie Chimiche
- Università della Calabria
- Arcavacata di Rende (CS)
- Italy
| | - Christie Aroulanda
- Equipe de RMN en milieu orienté
- ICMMO
- UMR 8182 CNRS
- Université Paris-Sud
- Orsay
| | - Giorgio Celebre
- Lab. LXNMR_S.C.An
- Dipartimento di Chimica e Tecnologie Chimiche
- Università della Calabria
- Arcavacata di Rende (CS)
- Italy
| | - Denis Merlet
- Equipe de RMN en milieu orienté
- ICMMO
- UMR 8182 CNRS
- Université Paris-Sud
- Orsay
| | - Giuseppina De Luca
- Lab. LXNMR_S.C.An
- Dipartimento di Chimica e Tecnologie Chimiche
- Università della Calabria
- Arcavacata di Rende (CS)
- Italy
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9
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Lesot P, Aroulanda C, Zimmermann H, Luz Z. Enantiotopic discrimination in the NMR spectrum of prochiral solutes in chiral liquid crystals. Chem Soc Rev 2015; 44:2330-75. [DOI: 10.1039/c4cs00260a] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Theory and applications to stereo- and bio-chemistry of the discrimination of enantiotopic elements observed in the NMR spectra of prochiral solutes dissolved in chiral liquid crystals are comprehensively discussed.
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Affiliation(s)
- Philippe Lesot
- Laboratoire de RMN en Milieu Orienté CNRS UMR 8182
- ICMMO
- 91405 Orsay cedex
- France
| | - Christie Aroulanda
- Laboratoire de RMN en Milieu Orienté CNRS UMR 8182
- ICMMO
- 91405 Orsay cedex
- France
| | - Herbert Zimmermann
- Abteilung Biophysik
- Max-Planck-Institut für Medizinische Forschung
- 69120 Heidelberg
- Germany
| | - Zeev Luz
- Weizmann Institute of Science
- Department of Chemical Physics
- Rehovot 76100
- Israel
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10
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Di Pietro ME, Aroulanda C, Merlet D, Celebre G, De Luca G. Conformational Investigation in Solution of a Fluorinated Anti-inflammatory Drug by NMR Spectroscopy in Weakly Ordering Media. J Phys Chem B 2014; 118:9007-16. [DOI: 10.1021/jp505084g] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Maria Enrica Di Pietro
- Dipartimento
di Chimica e Tecnologie Chimiche, Università della Calabria, via P.
Bucci, 87036, Arcavacata
di Rende, Cosenza, Italy
- Equipe
de RMN
en milieu orienté, ICMMO, UMR 8182, Université Paris-Sud, 15 Rue Georges Clemenceau, 91405 Orsay, France
| | - Christie Aroulanda
- Equipe
de RMN
en milieu orienté, ICMMO, UMR 8182, Université Paris-Sud, 15 Rue Georges Clemenceau, 91405 Orsay, France
| | - Denis Merlet
- Equipe
de RMN
en milieu orienté, ICMMO, UMR 8182, Université Paris-Sud, 15 Rue Georges Clemenceau, 91405 Orsay, France
| | - Giorgio Celebre
- Dipartimento
di Chimica e Tecnologie Chimiche, Università della Calabria, via P.
Bucci, 87036, Arcavacata
di Rende, Cosenza, Italy
| | - Giuseppina De Luca
- Dipartimento
di Chimica e Tecnologie Chimiche, Università della Calabria, via P.
Bucci, 87036, Arcavacata
di Rende, Cosenza, Italy
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11
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Badawi HM. A comparative study of the structure and vibrational spectra of diphenylmethane, the carcinogen 4,4'-methylenedianiline and 4,4'-methylenebis(N,N-dimethylaniline). SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2013; 109:213-220. [PMID: 23528920 DOI: 10.1016/j.saa.2013.02.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 02/07/2013] [Accepted: 02/12/2013] [Indexed: 06/02/2023]
Abstract
The structural stability of 4,4'-methylenedianiline (MDA), 4,4'-methylenebis(N,N-dimethylaniline) (MBDMA) and their parent diphenylmethane (DPM) was investigated by the DFT-B3LYP and ab initio MP2 calculations with the 6-311G(**) basis set. From the calculations the three diphenylmethanes were predicted to exist predominantly in a non-planar structure with a near C2 molecular symmetry in agreement with X-ray studies. The CCCC angles in DPM and the two dianilines were calculated to be nearly equal of about 60° as compared to X-ray angles of 17° and 67° for MDA. The NH2 inversion barriers in MDA was estimated to be about 1-5 kcal/mol. On comparison of the Raman spectra of the three compounds, the line intensity and position of the characteristic ring breathing mode were shown to be sensitive to the amino substitution. The vibrational wavenumbers of the optimized structures of the two dianilines were computed at the DFT-B3LYP level of theory. Tentative vibrational assignments were made on the basis of combined DFT and experimental FT-IR and FT-Raman data of MDA and MBDMA.
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Affiliation(s)
- Hassan M Badawi
- Department of Chemistry, King Fahd University of Peteroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia.
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12
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Celebre G, De Luca G, Di Pietro ME. The stable conformations of 4,4′-dichloro-trans-stilbene in solution by liquid crystal NMR spectroscopy. J Mol Struct 2013. [DOI: 10.1016/j.molstruc.2012.10.057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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13
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Celebre G, De Luca G, Di Pietro ME. Conformational Distribution of trans-Stilbene in Solution Investigated by Liquid Crystal NMR Spectroscopy and Compared with in Vacuo Theoretical Predictions. J Phys Chem B 2012; 116:2876-85. [DOI: 10.1021/jp211962w] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Giorgio Celebre
- Dipartimento di Chimica, Università della Calabria, v. P. Bucci, I-87036
Rende (CS), Italy
| | - Giuseppina De Luca
- Dipartimento di Chimica, Università della Calabria, v. P. Bucci, I-87036
Rende (CS), Italy
| | - Maria Enrica Di Pietro
- Dipartimento di Chimica, Università della Calabria, v. P. Bucci, I-87036
Rende (CS), Italy
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14
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De Luca G, Emsley JW, Salager E, Lesage A. A general strategy for obtaining 19F-19F and 13C-19F residual dipolar couplings in perfluorocarbons from the NMR spectroscopy of liquid crystalline samples. Phys Chem Chem Phys 2010; 12:7968-76. [PMID: 20514384 DOI: 10.1039/c002817g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A two-dimensional Fluorine Detected Local Field (FDLF) NMR experiment is demonstrated on a sample of perfluoropropyl iodide dissolved in the nematic solvent ZLI1132. In analogy to the proton detected local field (PDLF) technique, for each resolved site of the carbon spectrum, a simple map of the heteronuclear coupling network is obtained in the indirect dimension. A full analysis of the FDLF spectrum was achieved with the aid of two-dimensional (19)F-(13)C HETCOR and (13)C, D-resolved spectra (with D representing the anisotropic spin-spin coupling). A one-dimensional (19)F spectrum was recorded on the same sample at intermediate resolution, and values of the residual spin-spin couplings T(CF) and T(FF) obtained from both experiments were combined and used to provide starting parameters for the analysis of a very high resolution (19)F spectrum, including the weak satellite lines from single-(13)C isotopomers. The high-precision, residual, anisotropic couplings were used to explore whether they have an appreciable contribution from the anisotropic electron-mediated spin-spin couplings.
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Affiliation(s)
- Giuseppina De Luca
- Dipartimento di Chimica, Universita della Calabria, 87030 Arcavacata di Rende, Italy
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15
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Emsley JW, Lesot P, Lesage A, De Luca G, Merlet D, Pileio G. The conformation and orientational order of a 1,2-disubstituted ethane nematogenic molecule (I22) in liquid crystalline and isotropic phases studied by NMR spectroscopy. Phys Chem Chem Phys 2010; 12:2895-914. [PMID: 20449380 DOI: 10.1039/b915587b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- James W Emsley
- School of Chemistry, University of Southampton, Southampton, UKSO17 1BJ.
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16
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Sahakyan AB, Shahkhatuni AG, Shahkhatuni AA, Panosyan HA. Torsion sensitivity in NMR of aligned molecules: study on various substituted biphenyls. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46:144-149. [PMID: 18095265 DOI: 10.1002/mrc.2142] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
To estimate the torsion sensitivity of dipolar coupling, biphenylic molecules were chosen as probes due to their relatively simple structure and the surprisingly high ambiguity of the only flexible parameter-the interring torsion angle. Solution structures of 4,4'-dibromobiphenyl and 4,4'-diiodobiphenyl are reported for the first time in two liquid crystals I52 and ZLI 1695. The comparison of NMR structures of various para-substituted biphenyls (BPs), calculated by the additive potential maximum entropy (APME) approach, shows that the small spread of torsion angle values in case of different solvents and para-substituents is in good agreement with theoretical expectations from hybrid density functional theory (DFT) methods. Furthermore, the real structural changes of interring torsion and the prevalence of solvent effects over para-halosubstitution can be correctly revealed from these small fluctuations.
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Affiliation(s)
- Aleksandr B Sahakyan
- Molecule Structure Research Center of National Academy of Sciences, Yerevan 0014, Armenia.
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17
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Thaning J, Högberg CJ, Stevensson B, Lyubartsev AP, Maliniak A. Molecular Conformations in a Phospholipid Bilayer Extracted from Dipolar Couplings: A Computer Simulation Study. J Phys Chem B 2007; 111:13638-44. [DOI: 10.1021/jp075278t] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Johan Thaning
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Carl-Johan Högberg
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Baltzar Stevensson
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Alexander P. Lyubartsev
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Arnold Maliniak
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
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Celebre G, Concistré M, De Luca G, Longeri M, Pileio G. Intrinsic Information Content of NMR Dipolar Couplings: A Conformational Investigation of 1,3-Butadiene in a Nematic Phase. Chemphyschem 2006; 7:1930-43. [PMID: 16871617 DOI: 10.1002/cphc.200600220] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The conformational equilibrium of 1,3-butadiene in a condensed fluid phase is investigated by liquid-crystal NMR spectroscopy. The full set of D(HH) and D(CH) dipolar couplings is determined from the analysis of the (1)H spectra of the three 1,3-butadiene most-abundant isotopomers (i.e. the all (12)C and the two single-labeled (13)C isotopomers) for a total of 21 independent dipolar couplings. A very good starting set of spectral parameters for the analysis of the (1)H spectrum is determined in a semiautomated way by the analysis of the (N-1) (specifically, N=6, the number of 1/2 spin nuclei in the spin system) quantum refocused (5QR), and not (5Q), spectra. As an alternative approach, a Monte Carlo (MC) numerical simulation, capable of predicting the solute ordering, is tested to simulate the 5QR spectrum. The set of D(ij) couplings is very good, proving that the MC method can represent a novel, valid alternative to the existing spectral simplification procedures. The experimentally determined dipolar-coupling data set is fully compatible with the 1,3-butadiene conformational distribution reported in the literature for isolated molecules, indicating the presence of about 99 % of s-trans conformer. With regards to the remaining 1 %, in spite of the direct and very strong dependence of the observables on the molecular structure, it was not possible to discriminate between the planar s-cis and s-gauche forms, both of which produce a very good fit of the dipolar couplings. Vibrational corrections, up to the anharmonic term, were applied; the calculated geometrical parameters are in good- although not exact-agreement with those reported in the literature from experimental and theoretical investigations. This result can be considered as supporting the methodology used for obtaining the structure and conformational distribution of a flexible molecule in a liquid phase.
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Affiliation(s)
- Giorgio Celebre
- Universitá della Calabria, Dipartimento di Chimica Via P. Bucci, 87030 Arcavacata di Rende (Cs), Italy
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Emsley JW, Longeri M, Merlet D, Pileio G, Suryaprakash N. An investigation of the structure and bond rotational potential of some fluorinated ethanes by NMR spectroscopy of solutions in nematic liquid crystalline solvents. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 180:245-55. [PMID: 16554180 DOI: 10.1016/j.jmr.2006.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2006] [Revised: 02/24/2006] [Accepted: 03/01/2006] [Indexed: 05/07/2023]
Abstract
NMR spectra of 1,2-dibromo-1,1-difluoroethane and 1-bromo-2-iodo-tetrafluoroethane dissolved in nematic liquid crystalline solvents have been analysed to yield the magnitudes and signs of the scalar couplings, J(ij), and total anisotropic couplings, T(ij), between all the (1)H, (19)F, and (13)C nuclei, except for those between two (13)C nuclei. The values obtained for T(ij) in principle contain a contribution from J(ij)(aniso), the component along the static applied magnetic field of the anisotropic part of the electron-mediated spin-spin coupling. Neglecting this contribution allows partially averaged dipolar couplings, D(ij), to be extracted from the T(ij), and these were used to determine the structure, orientational order, and the conformational distribution generated by rotation about the C-C bond. The values obtained are compared with the results of calculations by ab initio and density functional methods. The differences found are no greater than those obtained for similar compounds which do not contain fluorine, so that there is no definitive evidence for significant contributions from J(CF)(aniso) or J(FF)(aniso) in the two compounds studied.
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Affiliation(s)
- J W Emsley
- Department of Chemistry, Universita della Calabria, Arcavacata di Rende, Italy.
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Celebre G, De Luca G, Emsley JW, Longeri M, Merlet D, Pileio G, Suryaprakash N. Obtaining the structure and bond rotational potential of a substituted ethane by NMR spectroscopy of solutions in nematic liquid-crystalline solvents. J Chem Phys 2005; 123:194907. [PMID: 16321113 DOI: 10.1063/1.2121628] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Partially averaged dipolar couplings (also referred to as residual dipolar couplings) D(ij) can be obtained from the analysis of the NMR spectra of molecules dissolved in liquid-crystalline solvents. Their values for a nonrigid molecule depend upon the bond lengths and angles, the rotational potentials, and the orientational order of the molecules. The molecule studied, 1-chloro-2-bromoethane, is one of the simplest example of a substituted alkane in which the rotational potential has three minimum-energy positions, trans and gauche+/-conformations, and the present investigation explores the problems inherent in deriving the form of the potential and the molecular geometry from the set of partially averaged couplings between the protons, and between protons and (13)C nuclei. The geometrical parameters and the rotational potential obtained are compared with the results from a density-functional theory method.
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Affiliation(s)
- G Celebre
- Department of Chemistry, Universita della Calabria, Arcavacata di Rende, 87036 Rende, Italy
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21
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Concistré M, De Lorenzo L, De Luca G, Longeri M, Pileio G, Raos G. Conformational Analysis of 2,2‘-Bithiophene: A 1H Liquid Crystal NMR Study Using the 13C Satellite Spectra. J Phys Chem A 2005; 109:9953-63. [PMID: 16838912 DOI: 10.1021/jp054003f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have obtained a very large data set of spectral parameters from the analysis of (1)H NMR and (13)C satellite spectra of 2,2'-bithiophene dissolved in anisotropic, partially orienting mesophases. In particular, this parameter set includes 33 dipolar couplings, which are directly related to the interatomic distances, the dihedral angle phi between the two thiophenic rings, and the anisotropic solute-solvent interaction potential. This allows an exhaustive investigation of the conformational equilibrium of 2,2'-bithiophene in a liquidlike phase. Comparison with the predictions of high-level theoretical calculations for the isolated molecule provides evidence of a strong flattening as well as the sharpening effect of the medium on the conformer population. The approximations needed to apply vibrational corrections to flexible molecules are discussed in detail and some general conclusions concerning their effect on structure and conformational equilibria are proposed.
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Affiliation(s)
- Maria Concistré
- Dipartimento di Chimica, Universita della Calabria, Via P. Bucci, 87030 Arcavacata di Rende (Cs), Italy
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De Luca G, Longeri M, Pileio G, Lantto P. NMR Spectroscopy Investigation of the Cooperative Nature of the Internal Rotational Motions in Acetophenone. Chemphyschem 2005; 6:2086-98. [PMID: 16208750 DOI: 10.1002/cphc.200500134] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The proton NMR spectrum of the doubly enriched acetophenone-carbonyl,methyl-13C2 isotopomer dissolved in a liquid-crystalline solvent (LXNMR) was analyzed to yield a data set of 19 dipolar couplings. The presence of so many couplings, and in particular the dependence of some of them on the acetyl carbons enabled the investigation of the structure of the acetyl moiety and of possible cooperative motions about the aryl-carbonyl and carbonyl-methyl bonds. Methodological aspects, and approximations relating to the application of the vibrational correction procedure in the presence of large-amplitude torsional motions, are discussed. Results show that it is possible to discriminate between a continuous and a discrete conformer distribution about the angle phi(1) but not among a few proposed continuous shapes of U(iso)({phi}). In this study, the use of dipolar couplings with a non-negligible contribution from the indirect spin-spin coupling tensor J, (D(C8C9) in our case), for structural determination is extended from rigid to flexible molecules. The 1/2J(aniso)(C8C9) contribution was derived theoretically using the density functional theory linear response (DFT-LR) first-principles calculation of the J(C8C9) spin-spin coupling tensor.
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Affiliation(s)
- Giuseppina De Luca
- Universitá della Calabria, Dipartimento di Chimica, Via P. Bucci, 87030 Arcavacata di Rende Cs, Italy
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Concistrè M, De Luca G, Longeri M, Pileio G, Emsley JW. The Structure and Conformations of 2-Thiophenecarboxaldehyde Obtained from Partially Averaged Dipolar Couplings. Chemphyschem 2005; 6:1483-91. [PMID: 16082671 DOI: 10.1002/cphc.200500190] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The proton NMR spectra of samples of 2-thiophenecarboxaldehyde dissolved in a nematic liquid crystalline solvent, including those from all five singly labelled 13C isotopomers, have been obtained. These have been analysed to yield sets of partially averaged dipolar couplings which have been used to determine the structure and the relative amounts of the cis and trans forms, which are the two minimum-energy structures generated by rotation about the ring-aldehyde bond. A procedure for applying vibrational corrections to the dipolar couplings in the presence of large amplitude motions is discussed.
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Affiliation(s)
- Maria Concistrè
- Dipartimento di Chimica, Università della Calabria, Via P. Bucci, 87030, Arcavacata, Rende (Cs), Italy
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Celebre G, De Luca G, Maiorino M, Iemma F, Ferrarini A, Pieraccini S, Spada GP. Solute−Solvent Interactions and Chiral Induction in Liquid Crystals. J Am Chem Soc 2005; 127:11736-44. [PMID: 16104751 DOI: 10.1021/ja051589a] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The induction of a cholesteric phase by doping an achiral nematic liquid crystal with an enantiopure solute is a phenomenon that, as in all general supramolecular phenomena of chiral amplification, depends in a subtle way on intermolecular interactions. The micrometric helical deformation of the phase director in the cholesteric phase is generated by the interplay of anisotropy and chirality of probe-medium interactions. In the case of a flexible chiral dopant, the solvent can influence the twisting power in two ways, difficult to disentangle: it is responsible for the solute orientational order, an essential ingredient for the emergence of phase chirality; but also it can affect the dopant conformational distribution and then the chirality of the structures present in the solution. In this work we have investigated methyl phenyl sulfoxide, a flexible, chiral molecule that, when dissolved in different nematics, can produce cholesteric phases of opposite handedness. This peculiar, intriguing sensitivity to the environment makes MPS a suitable probe for a thorough investigation of the effects of solute-solvent interactions on chiral induction in liquid crystals. NMR experiments in various nematic solvents have been performed in addition to twisting power measurements. From the analysis of partially averaged 1H-1H and 13C-1H dipolar couplings, the effects of solvent on solute conformation and orientational order are disentangled, and this information is combined with the modeling of the chirality of intermolecular interactions, within a molecular field theory. The integration of different techniques allows an unprecedented insight into the role of solvent in mediating the chirality transfer from molecule to phase.
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Affiliation(s)
- Giorgio Celebre
- Dipartimento di Chimica, Università della Calabria, via P. Bucci, 87036 Rende (CS), Italy.
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Thaning J, Stevensson B, Maliniak A. Molecular structure extracted from residual dipolar couplings: Diphenylmethane dissolved in a nematic liquid crystal. J Chem Phys 2005; 123:044507. [PMID: 16095369 DOI: 10.1063/1.1950629] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This paper describes an analysis of 1H-1H residual dipolar couplings (RDCs) in diphenylmethane (DPM) dissolved in a nematic liquid crystal, reported by Celebre et al. [J. Chem. Phys. 118, 6417 (2003)]. In that article, the conformational distribution function for DPM was extracted from the RDCs, using the additive potential (AP) model which is based on the molecular-field theory. The AP approach is a powerful, and frequently used, tool for analysis of the nuclear-magnetic-resonance (NMR) parameters in liquid crystals. It requires, however, a priori knowledge of the functional form of the torsional potential, which may even for a simple molecule, such as DPM, be complicated to determine. Here, we analyze the same set of the RDCs using our APME procedure, which is a hybrid model based on the AP approach and maximum entropy (ME) theory. The APME procedure does not require any assumptions about the functional form of the torsional potential and, in contrast with the ME method, is applicable to weakly ordered systems. In the investigation reported in the present study, the results from the APME analysis are in good agreement with the AP interpretation, whereas the ME approach essentially fails in the extraction of the conformational distribution function for DPM.
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Affiliation(s)
- Johan Thaning
- Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
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Celebre G, Concistrè M, De Luca G, Longeri M, Pileio G, Emsley JW. The Structure of Acrolein in a Liquid Crystal Phase. Chemistry 2005; 11:3599-608. [PMID: 15809986 DOI: 10.1002/chem.200401059] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The (1)H NMR spectrum of a sample of acrolein dissolved in the nematic liquid crystal phase I52 has been analysed to yield 18 dipolar couplings between all the magnetic nuclei in the molecule; moreover, the (13)C and (13)C{(1)H} NMR spectra of a sample of acrolein in CDCl(3) were recorded and analysed to determine the indirect J(ij) couplings. The data were used to obtain the relative positions of the carbon and hydrogen atoms, assuming that these are independent of the conformations generated by rotation around the C--C bond through an angle phi, and to obtain a probability distribution P(phi). It has been found that in the liquid phase, the distribution is a maximum at the trans form whereas the abundance of the cis form is significantly smaller compared with that found by microwave spectroscopy or high level quantum mechanical calculations. Such calculations produced also a suitable force field needed to develop suitable strategies for vibrational correction procedure in the case of flexible molecules.
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Affiliation(s)
- Giorgio Celebre
- Università della Calabria, Dipartimento di Chimica, Arcavacata di Rende (Cs), Italy
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Celebre G, De Luca G, Longeri M, Pileio G, Emsley JW. Is styrene planar in liquid phases? J Chem Phys 2004; 120:7075-84. [PMID: 15267611 DOI: 10.1063/1.1668636] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The proton NMR spectra of two (13)C-labeled isotopomers of styrene dissolved in two liquid crystalline solvents have been obtained and analyzed to yield four sets each of 24 dipolar couplings. These couplings were then used to investigate the structure of the ring and the ene fragments of the molecule, and the position of the maximum, phi(0), in the ring-ene bond rotational probability distribution. To do this, the effect on the dipolar couplings of small-amplitude vibrational motion was taken into account using vibrational wave functions calculated by molecular orbital and density functional methods. It is concluded that the NMR data are consistent with the ring fragment, averaged over the ring-ene rotation, planar, while the ene fragment is not. The value of phi(0) is found to be 18.0 degrees +/-0.2 degrees for the two solutions, compared with a value of 27 degrees calculated by the molecular method MP2/6-31G(*).
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Affiliation(s)
- Giorgio Celebre
- Dipartimento di Chimica, Università della Calabria, Rende (CS), 87036, Italy.
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