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Dominant changes in centre Fe atom of decamethyl-ferrocene from ferrocene in methylation. Theor Chem Acc 2023. [DOI: 10.1007/s00214-022-02949-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
AbstractStaggered decamethyl-ferrocene (*Fc) becomes the lower energy conformer at low temperature, whereas the eclipsed conformer of ferrocene (Fc) is more stable. The powerful infrared (IR) spectroscopy which has remarkably provided signatures of ferrocene (Fc) in eclipsed and staggered conformers recently is employed to investigate methylation of Fc. The most significant consequences of the full methylation of Fc in the IR spectra are the blue shift of the band at ~ 800 cm−1 in Fc to ~ 1500 cm−1 in *Fc, and the enhancement of the C–H stretch band at ~ 3200 cm−1 region in *Fc. Further analysis reveals large impact of Fc methylation on core electron energies of the centre Fe atom (1s22s22p63s23p6). The Fe core electron energy changes can be as large as ~ 10 kcal mol−1 and are directional—the Fe 2pz and 3pz orbitals along the *Cp–Fe–*Cp axis (Cp centroids, vertical) change more strongly than other Fe core electrons in px and py orbitals. The directional inner shell energy changes are evidenced by larger inner shell reorganization energy. Energy decomposition analysis (EDA) indicates that methyl groups in *Fc apparently change the physical energy components with respect to Fc. The large steric energy of *Fc evidences that the closest hydrogens on adjacent methyl groups of the same *Cp ring in crystal structure are 0.2–0.4 Å closer than the hydrogens on nearest-neighbour methyl groups on opposing rings in *Fc. A significant increase in Pauli repulsive energy contributes to the large repulsive steric energy in *Fc.
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Oemry F, Adilina IB, Cahyanto WT, Rinaldi N, Aulia F, Jackson A, Parker SF, Kroner AB, Shotton EJ. Experimental and computational studies of sulfided NiMo supported on pillared clay: catalyst activation and guaiacol adsorption sites. Phys Chem Chem Phys 2023; 25:2978-2989. [PMID: 36606490 DOI: 10.1039/d2cp03987g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We report on intermediate (oxysulfides) and sulfided structures of NiMo supported on aluminium pillared clay (Al-PILC) during the catalyst activation process and the prefered guaiacol adsorption sites on the sulfided catalyst. In situ X-ray absorption fine structure (XAFS) together with density functional theory (DFT) calculations confirm the existence of ill-defined suboxides (MoOx, NiOx) and the well-known subsulfides (Mo2S9, Ni3S2) at the first stage which, at a later stage in the process, transform into MoS2 with two edges, oxygen-decorated Mo and Ni with zero sulfur coverage. The freshly sulfided NiMoS2 catalyst under sulfiding agents is mainly terminated by Mo-edge surface with 50% sulfur coverage (Mo-S50) with a disordered Ni-edge surface that can be assigned as NiMoS (1̄010). When exposed to an inert atmosphere such as He gas, the Mo and Ni edges evolved partially into new structures of Mo and Ni edges with zero sulfur coverage, labelled as Mo-Bare and Ni-Bare. Guaiacol is often used as a model compound for lignin and a series of calculations of guaiacol on the structural edges of a sulfided NiMoS2 catalyst show relatively good agreement between the observed and calculated inelastic neutron scattering (INS) spectra for Mo-S50, Ni-Bare, and NiMoS (1̄010) where guaiacol weakly chemisorbed via oxygen atom of OH group. The results also confirm that guaiacol is physisorbed on the basal plane of NiMoS2 in a horizontal (flat-lying) configuration via van der Waals interaction at a separation of about 3.25 Å.
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Affiliation(s)
- F Oemry
- Research Center for Quantum Physics, National Research and Innovation Agency, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15314, Indonesia.
| | - I B Adilina
- Research Center for Advanced Chemistry, National Research and Innovation Agency, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15314, Indonesia
| | - W T Cahyanto
- Department of Physics, Universitas Jenderal Soedirman, Jl. dr. Soeparno 61, Purwokerto, 53122, Indonesia
| | - N Rinaldi
- Research Center for Advanced Chemistry, National Research and Innovation Agency, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15314, Indonesia
| | - F Aulia
- Research Center for Advanced Chemistry, National Research and Innovation Agency, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15314, Indonesia
| | - A Jackson
- Scientific Computing Department, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
| | - S F Parker
- ISIS Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
| | - A B Kroner
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
| | - E J Shotton
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
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Nolasco MM, Coimbra MM, Parker SF, Vaz PD, Ribeiro-Claro PJA. Structural Dynamics of Chloromethanes through Computational Spectroscopy: Combining INS and DFT. Molecules 2022; 27:molecules27217661. [PMID: 36364488 PMCID: PMC9655087 DOI: 10.3390/molecules27217661] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 11/02/2022] [Accepted: 11/04/2022] [Indexed: 11/09/2022] Open
Abstract
In this work, the structural dynamics of the chloromethanes CCl4, CHCl3 and CH2Cl2 were evaluated through a computational spectroscopy approach by comparing experimental inelastic neutron scattering (INS) spectra with the corresponding simulated spectra obtained from periodic DFT calculations. The overall excellent agreement between experimental and calculated spectra allows a confident assignment of the vibrational features, including not only the molecular fundamental modes but also lattice and combination modes. In particular, an impressive overtone sequence for CHCl3 is fully described by the simulated INS spectrum. In the CCl4 spectrum, the splitting of the ν3 mode at ca. 765–790 cm−1 is discussed on the basis of the Fermi resonance vs. crystal splitting controversy.
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Affiliation(s)
- Mariela M. Nolasco
- CICECO—Instituto de Materiais de Aveiro, Departamento de Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal
- Correspondence:
| | - Mariana Matos Coimbra
- CICECO—Instituto de Materiais de Aveiro, Departamento de Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal
| | - Stewart F. Parker
- ISIS Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK
| | - Pedro D. Vaz
- Champalimaud Foundation, Champalimaud Centre for the Unknown, 1400-038 Lisboa, Portugal
| | - Paulo J. A. Ribeiro-Claro
- CICECO—Instituto de Materiais de Aveiro, Departamento de Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal
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The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy. Molecules 2022; 27:molecules27123948. [PMID: 35745072 PMCID: PMC9230607 DOI: 10.3390/molecules27123948] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/27/2022] [Accepted: 06/06/2022] [Indexed: 11/17/2022] Open
Abstract
Large amplitude motions (LAMs) form a fundamental phenomenon that demands the development of specific theoretical and Hamiltonian models. In recent years, along with the strong progress in instrumental techniques on high-resolution microwave spectroscopy and computational capacity in quantum chemistry, studies on LAMs have become very diverse. Larger and more complex molecular systems have been taken under investigation, ranging from series of heteroaromatic molecules from five- and six-membered rings to polycyclic-aromatic-hydrocarbon derivatives. Such systems are ideally suited to create families of molecules in which the positions and the number of LAMs can be varied, while the heteroatoms often provide a sufficient dipole moment to the systems to warrant the observation of their rotational spectra. This review will summarize three types of LAMs: internal rotation, inversion tunneling, and ring puckering, which are frequently observed in aromatic five-membered rings such as furan, thiophene, pyrrole, thiazole, and oxazole derivatives, in aromatic six-membered rings such as benzene, pyridine, and pyrimidine derivatives, and larger combined rings such as naphthalene, indole, and indan derivatives. For each molecular class, we will present the representatives and summarize the recent insights on the molecular structure and internal dynamics and how they help to advance the field of quantum mechanics.
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Vibrational Dynamics in crystalline 4-(dimethylamino) benzaldehyde: Inelastic Neutron Scattering and Periodic DFT Study. MATERIALS 2022; 15:ma15020475. [PMID: 35057193 PMCID: PMC8780805 DOI: 10.3390/ma15020475] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/05/2022] [Accepted: 01/05/2022] [Indexed: 01/04/2023]
Abstract
The structure and dynamics of crystalline 4-(dimethylamino) benzaldehyde, 4DMAB, are assessed through INS spectroscopy combined with periodic DFT calculations. The excellent agreement between experimental and calculated spectra is the basis for a reliable assignment of INS bands. The external phonon modes of crystalline 4DMAB are quite well described by the simulated spectrum, as well as the modes involving low-frequency molecular vibrations. Crystal field splitting is predicted and observed for the modes assigned to the dimethylamino group. Concerning the torsional motion of methyl groups, four individual bands are identified and assigned to specific methyl groups in the asymmetric unit. The torsional frequencies of the four methyl groups in the asymmetric unit fall in a region of ca. 190 ± 20 cm-1, close to the range of values observed for methyl groups bonding to unsaturated carbon atoms. The hybridization state of the X atom in X-CH3 seems to play a key role in determining the methyl torsional frequency.
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How Many Molecules Can Fit in a Zeolite Pore? Implications for the Hydrocarbon Pool Mechanism of the Methanol-to-Hydrocarbons Process. Catalysts 2021. [DOI: 10.3390/catal11101204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The methanol-to-hydrocarbons (MTH) process is a very advantageous way to upgrade methanol to more valuable commodity chemicals such as light alkenes and gasoline. There is general agreement that, at steady state, the process operates via a dual cycle “hydrocarbon pool” mechanism. This mechanism defines a minimum number of reactants, intermediates, and products that must be present for the reaction to occur. In this paper, we calculate (by three independent methods) the volume required for a range of compounds that must be present in a working catalyst. These are compared to the available volume in a range of zeolites that have been used, or tested, for MTH. We show that this straightforward comparison provides a means to rationalize the product slate and the deactivation pathways in zeotype materials used for the MTH reaction.
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New Insights on the Vibrational Dynamics of 2-Methoxy-, 4-Methoxy- and 4-Ethoxy-Benzaldehyde from INS Spectra and Periodic DFT Calculations. MATERIALS 2021; 14:ma14164561. [PMID: 34443083 PMCID: PMC8399430 DOI: 10.3390/ma14164561] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 07/29/2021] [Accepted: 08/05/2021] [Indexed: 12/01/2022]
Abstract
The dynamics of 2-methoxybenzaldehyde, 4-methoxybenzaldehyde, and 4-ethoxybenzaldehyde in the solid state are assessed through INS spectroscopy combined with periodic DFT calculations. In the absence of experimental data for 4-ethoxybenzaldehyde, a tentative crystal structure, based on its similarity with 4-methoxybenzaldehyde, is considered and evaluated. The excellent agreement between calculated and experimental spectra allows a confident assignment of the vibrational modes. Several spectral features in the INS spectra are unambiguously assigned and torsional potential barriers for the methyl groups are derived from experimental frequencies. The intramolecular nature of the potential energy barrier for methyl rotation about O–CH3 bonds compares with the one reported for torsion about saturated C–CH3 bonds. On the other hand, the intermolecular contribution to the potential energy barrier may represent 1/3 of the barrier height in these systems.
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Zachariou A, Hawkins AP, Suwardiyanto, Collier P, Barrow N, Howe RF, Parker SF, Lennon D. New Spectroscopic Insight into the Deactivation of a ZSM‐5 Methanol‐to‐Hydrocarbons Catalyst. ChemCatChem 2021. [DOI: 10.1002/cctc.202100286] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Andrea Zachariou
- School of Chemistry University of Glasgow Joseph Black Building Glasgow G12 8QQ UK
- UK Catalysis Hub Research Complex at Harwell STFC Rutherford Appleton Laboratory Chilton, Oxon OX11 0FA UK
| | - Alexander P. Hawkins
- School of Chemistry University of Glasgow Joseph Black Building Glasgow G12 8QQ UK
- UK Catalysis Hub Research Complex at Harwell STFC Rutherford Appleton Laboratory Chilton, Oxon OX11 0FA UK
| | - Suwardiyanto
- Department of Chemistry University of Jember Jember 68121 East Java Indonesia
| | - Paul Collier
- Johnson Matthey Plc. Johnson Matthey Technology Centre Blounts Court Sonning Common Reading RG4 9NH UK
| | - Nathan Barrow
- Johnson Matthey Plc. Johnson Matthey Technology Centre Blounts Court Sonning Common Reading RG4 9NH UK
| | - Russell F. Howe
- Department of Chemistry University of Aberdeen Meston Building Aberdeen AB24 3UE UK
| | - Stewart F. Parker
- School of Chemistry University of Glasgow Joseph Black Building Glasgow G12 8QQ UK
- UK Catalysis Hub Research Complex at Harwell STFC Rutherford Appleton Laboratory Chilton, Oxon OX11 0FA UK
- ISIS Neutron and Muon Source ISIS Facility STFC Rutherford Appleton Laboratory Chilton, Oxon OX11 0QX UK
| | - David Lennon
- School of Chemistry University of Glasgow Joseph Black Building Glasgow G12 8QQ UK
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