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Meinnel J, Zeroual S, Mahboub MS, Boucekkine A, Juranyi F, Carlile C, Mimouni M, Hamadneh I, Boudjada A. Calculations of the molecular interactions in 1,3-dibromo-2,4,6-trimethyl-benzene: which methyl groups are quasi-free rotors in the crystal? Phys Chem Chem Phys 2021; 23:21272-21285. [PMID: 34543373 DOI: 10.1039/d1cp02581c] [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
Dibromomesitylene (DBMH) is one of the few molecules in which a methyl group is a quasi-free rotor in the crystal state. Density functional theory calculations - using the Born-Oppenheimer approximation (BOa) - indicate that in isolated DBMH, Me4 and Me6 are highly hindered in a 3-fold potential V3 > 55 meV while Me2 symmetrically located between two Br atoms has a small 6-fold rotation hindering potential: V6 ∼ 8 meV. Inelastic neutron scattering studies have shown that this is also true in the crystal, the Me2 tunneling gap being 390 μeV at 4.2 K and V6 ∼ 18 meV. In the monoclinic DBMH crystal, molecules are packed in an anti-ferroelectric manner along the oblique a axis, favoring strong van der Waals interactions, while in the corrugated bc planes each molecule has a quasi hexagonal environment and weaker interactions. This results in the nearby environment of Me2 only being composed of hydrogen atoms. This explains why the Me2 rotation barrier remains small in the crystal and mainly 6-fold. Using the same potentials in the Schrödinger equation for a -CD3 rotor has allowed predicting a tunneling gap of 69 μeV for deuterated Me2 in very good agreement with inelastic neutron scattering measurements. Therefore, because of a rare and unexpected local symmetry in the crystal, the Me2 rotation barrier remains small and 6-fold and hydrogen nuclei are highly delocalized and not relevant to the Born-Oppenheimer approximation. This and the neglect of spin states explain the failure of density functional theory calculations for finding the rotation energy levels of Me2.
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Affiliation(s)
- Jean Meinnel
- Univ Rennes 1, CNRS, ISCR - UMR 6226, ssF-35000 Rennes, France
| | - Soria Zeroual
- LEVRES Laboratory, University of El Oued, 39000 El Oued, Algeria.
| | | | | | - Fanni Juranyi
- Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Colin Carlile
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | - Mourad Mimouni
- LEVRES Laboratory, University of El Oued, 39000 El Oued, Algeria.
| | - Imad Hamadneh
- Department of Chemistry, Faculty of Science, University of Jordan, Amman 11942, Jordan
| | - Ali Boudjada
- Laboratoire de Cristallographie, Département de Physique, Faculté des Sciences Exactes, Université des Frères Mentouri Constantine-1, 25000, Algeria
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Leela JSPP, Hemamalini R, Muthu S, Al-Saadi AA. Spectroscopic investigation (FTIR spectrum), NBO, HOMO-LUMO energies, NLO and thermodynamic properties of 8-Methyl-N-vanillyl-6-nonenamideby DFT methods. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2015; 146:177-186. [PMID: 25813174 DOI: 10.1016/j.saa.2015.03.027] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Revised: 01/23/2015] [Accepted: 03/01/2015] [Indexed: 06/04/2023]
Abstract
Capsicum a hill grown vegetable is also known as red pepper or chili pepper. Capsaicin(8-Methyl-N-vanillyl-6-nonenamide) is the active component in chili peppers, which is currently used in the treatment of osteoarthritis, psoriasis and cancer. Fourier transform infrared (FT-IR) spectrum of Capsaicin in the solid phase were recorded in the region 4000-400 cm(-1) and analyzed. The vibrational frequencies of the title compound were obtained theoretically by DFT/B3LYP calculations employing the standard 6-311++G(d,p) basis set and were compared with Fourier transform infrared spectrum. Complete vibrational assignment analysis and correlation of the fundamental modes for the title compound were carried out. The vibrational harmonic frequencies were scaled using scale factor, yielding a good agreement between the experimentally recorded and the theoretically calculated values. Stability of the molecule arising from hyper conjugative interactions, charge delocalization and intra molecular hydrogen bond-like weak interaction has been analyzed using Natural bond orbital (NBO) analysis by using B3LYP/6-311++G(d,p) method. The results show that electron density (ED) in the σ∗ and π∗ antibonding orbitals and second-order delocalization energies E (2) confirm the occurrence of intra molecular charge transfer (ICT) within the molecule. The dipole moment (μ), polarizability (α) and the hyperpolarizability (β) values of the molecule has been computed. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures were calculated.
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Affiliation(s)
| | - R Hemamalini
- PG & Research Department of Physics, Queen Mary's College, Tamilnadu, India
| | - S Muthu
- Department of Physics, Sri Venkateswara College of Engineering, Sriperumpudur 602105, Tamilnadu, India.
| | - Abdulaziz A Al-Saadi
- Department of Chemistry, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia
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Icker M, Fricke P, Grell T, Hollenbach J, Auer H, Berger S. Experimental boundaries of the quantum rotor induced polarization (QRIP) in liquid state NMR. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2013; 51:815-820. [PMID: 24214240 DOI: 10.1002/mrc.4021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 09/14/2013] [Accepted: 09/18/2013] [Indexed: 06/02/2023]
Abstract
The Haupt-effect is a rather seldom used hyperpolarization method. It is based on the interdependence between nuclear spin states and rotational states of nearly free rotating methyl groups having C3 symmetry. A sudden change in temperature from 4.2 K to room temperature by fast dissolution yields considerably enhanced (13)C and (1)H resonance signals. This phenomenon is now termed quantum rotor induced polarization. More than 40 substances have been studied by this approach in order to identify them as polarizable by the 'Haupt-effect in the liquid state'. Influencing factors have been analyzed systematically. It could be concluded that substances having a high tunneling frequency, which is due to a small and narrow potential barrier, are most likely to feature quantum rotor induced polarization-enhanced signals.
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Affiliation(s)
- Maik Icker
- Institute of Analytical Chemistry, University of Leipzig, Johannisallee 29, 04103, Leipzig, Germany
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Kose E, Atac A, Karabacak M, Nagabalasubramanian PB, Asiri AM, Periandy S. FT-IR and FT-Raman, NMR and UV spectroscopic investigation and hybrid computational (HF and DFT) analysis on the molecular structure of mesitylene. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2013; 116:622-634. [PMID: 23978748 DOI: 10.1016/j.saa.2013.07.070] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 07/08/2013] [Accepted: 07/25/2013] [Indexed: 06/02/2023]
Abstract
The spectroscopic properties of mesitylene were investigated by FT-IR, FT-Raman, UV, (1)H and (13)C NMR techniques. The geometrical parameters and energies have been obtained from density functional theory (DFT) B3LYP method and Hartree-Fock (HF) method with 6-311++G(d,p) and 6-311G(d,p) basis sets calculations. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (OPDOS) diagrams analysis were presented. (13)C and (1)H NMR chemical shifts were calculated by using the gauge-invariant atomic orbital (GIAO) method. The electronic properties, such as excitation energies, oscillator strength, wavelengths, HOMO and LUMO energies, were performed by time-dependent density functional theory (TD-DFT) results complements with the experimental findings. The results of the calculations were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) and thermodynamic properties were performed. Reduced density gradient (RDG) of the mesitylene was also given to investigate interactions of the molecule.
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Affiliation(s)
- E Kose
- Department of Physics, Celal Bayar University, Manisa, Turkey.
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Meinnel JJ, Boudjada A, Boucekkine A, Boudjada F, Moréac A, Parker SF. Vibrational Spectra of Triiodomesitylene: Combination of DFT Calculations and Experimental Studies. Effects of the Environment. J Phys Chem A 2008; 112:11124-41. [DOI: 10.1021/jp802621w] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jean J. Meinnel
- Laboratoire Sciences Chimiques de Rennes, UMR CNRS 6226 and Laboratoire Matière Condensée et Matériaux, UMR CNRS 6226, Université de Rennes 1, 35042 Rennes, France, Laboratoire de cristallographie, Faculté des Sciences, Université de Constantine, Constantine, Algerie, and Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX, U.K
| | - Ali Boudjada
- Laboratoire Sciences Chimiques de Rennes, UMR CNRS 6226 and Laboratoire Matière Condensée et Matériaux, UMR CNRS 6226, Université de Rennes 1, 35042 Rennes, France, Laboratoire de cristallographie, Faculté des Sciences, Université de Constantine, Constantine, Algerie, and Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX, U.K
| | - Abdou Boucekkine
- Laboratoire Sciences Chimiques de Rennes, UMR CNRS 6226 and Laboratoire Matière Condensée et Matériaux, UMR CNRS 6226, Université de Rennes 1, 35042 Rennes, France, Laboratoire de cristallographie, Faculté des Sciences, Université de Constantine, Constantine, Algerie, and Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX, U.K
| | - Fahima Boudjada
- Laboratoire Sciences Chimiques de Rennes, UMR CNRS 6226 and Laboratoire Matière Condensée et Matériaux, UMR CNRS 6226, Université de Rennes 1, 35042 Rennes, France, Laboratoire de cristallographie, Faculté des Sciences, Université de Constantine, Constantine, Algerie, and Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX, U.K
| | - Alain Moréac
- Laboratoire Sciences Chimiques de Rennes, UMR CNRS 6226 and Laboratoire Matière Condensée et Matériaux, UMR CNRS 6226, Université de Rennes 1, 35042 Rennes, France, Laboratoire de cristallographie, Faculté des Sciences, Université de Constantine, Constantine, Algerie, and Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX, U.K
| | - Stewart F. Parker
- Laboratoire Sciences Chimiques de Rennes, UMR CNRS 6226 and Laboratoire Matière Condensée et Matériaux, UMR CNRS 6226, Université de Rennes 1, 35042 Rennes, France, Laboratoire de cristallographie, Faculté des Sciences, Université de Constantine, Constantine, Algerie, and Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX, U.K
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