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Gupta S, Cummings CN, Walker NR, Arunan E. Microwave spectroscopic and computational analyses of the phenylacetylene⋯methanol complex: insights into intermolecular interactions. Phys Chem Chem Phys 2024; 26:19795-19811. [PMID: 38985163 DOI: 10.1039/d4cp01916d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2024]
Abstract
The microwave spectra of five isotopologues of phenylacetylene⋯methanol complex, C6H5CCH⋯CH3OH, C6H5CCH⋯CH3OD, C6H5CCH⋯CD3OD, C6H5CCD⋯CH3OH and C6H5CCH⋯13CH3OH, have been observed through Fourier transform microwave spectroscopy. Rotational spectra unambiguously unveil a specific structural arrangement characterised by dual interactions between the phenylacetylene and methanol. CH3OH serves as a hydrogen bond donor to the acetylenic π-cloud while concurrently accepting a hydrogen bond from the ortho C-H group of the PhAc moiety. The fitted rotational constants align closely with the structural configuration computed at the B3LYP-D3/aug-cc-pVDZ level of theory. The transitions of all isotopologues exhibit doublets owing to the methyl group's internal rotation within the methanol molecule. Comprehensive computational analyses, including natural bond orbital (NBO) analysis, atoms in molecules (AIM) theory, and non-covalent interactions (NCI) index plots, reveal the coexistence of both O-H⋯π and C-H⋯O hydrogen bonds within the complex. Symmetry adapted perturbation theory with density functional theory (SAPT-DFT) calculations performed on the experimentally determined geometry provide an insight into the prominent role of electrostatic interactions in stabilising the overall structural arrangement.
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Affiliation(s)
- Surabhi Gupta
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, 560012, India.
| | - Charlotte N Cummings
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Bedson Building, Newcastle-upon-Tyne NE1 7RU, UK
| | - Nicholas R Walker
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Bedson Building, Newcastle-upon-Tyne NE1 7RU, UK
| | - Elangannan Arunan
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, 560012, India.
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Antonelli E, Gougoula E, Walker NR, Schwell M, Nguyen HVL, Kleiner I. A global rho-axis method for fitting asymmetric tops with one methyl internal rotor and two 14N nuclei: Application of BELGI-2N to the microwave spectra of four methylimidazole isomers. J Chem Phys 2024; 160:214309. [PMID: 38836784 DOI: 10.1063/5.0207944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Accepted: 05/08/2024] [Indexed: 06/06/2024] Open
Abstract
A number of internal rotation codes can deal with the combination of one or two internal rotors with one 14N quadrupole nucleus, but once it comes to two 14N nuclei, no such code is available even for the case of one internal rotor. We present here the extension of our internal rotor program called BELGI-2N using the rho-axis method global approach to deal with compounds containing one methyl rotor and two weakly coupling 14N nuclei. To test our new code, we applied it to the microwave data recorded for N-methylimidazole, 2-methylimidazole, 4-methylimidazole, and 5-methylimidazole using a chirped-pulse Fourier transform microwave spectrometer in the 7.0-18.5 GHz frequency range. Compared to the previously published study, BELGI-2N was able to (i) significantly increase the number of assigned and fitted lines, (ii) fit the complete datasets considering both the internal rotation and the 14N nuclear quadrupole coupling effects simultaneously, and (iii) achieve standard deviations within the measurement accuracy for all methylimidazole isomers.
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Affiliation(s)
- Eléonore Antonelli
- Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France
| | - Eva Gougoula
- Chemistry, School of Natural and Environmental Sciences, Newcastle University, Bedson Building, Newcastle Upon Tyne NE1 7RU, United Kingdom
| | - Nicholas R Walker
- Chemistry, School of Natural and Environmental Sciences, Newcastle University, Bedson Building, Newcastle Upon Tyne NE1 7RU, United Kingdom
| | - Martin Schwell
- Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France
| | - Ha Vinh Lam Nguyen
- Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, F-94010 Créteil, France
- Institut Universitaire de France (IUF), F-75231 Paris, France
| | - Isabelle Kleiner
- Université Paris Cité and Univ Paris Est Creteil, CNRS, LISA, F-75013 Paris, France
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Cummings CN, Walker NR. Hydrogen Bonding and Molecular Geometry in Isolated Hydrates of 2-Ethylthiazole Characterised by Microwave Spectroscopy. Chemphyschem 2024; 25:e202400011. [PMID: 38314654 DOI: 10.1002/cphc.202400011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 02/02/2024] [Accepted: 02/02/2024] [Indexed: 02/06/2024]
Abstract
Broadband microwave spectra of the isolated 2-ethylthiazole molecule, and complexes of 2-ethylthiazole⋅⋅⋅H2O and 2-ethylthiazole⋅⋅⋅(H2O)2 have been recorded by probing a gaseous sample containing low concentrations of 2-ethylthiazole and water within a carrier gas undergoing supersonic expansion. The identified conformer of the isolated 2-ethylthiazole molecule and the 2-ethylthiazole sub-unit within each of 2-ethylthiazole⋅⋅⋅H2O and 2-ethylthiazole⋅⋅⋅(H2O)2 have C1 symmetry. The angle that defines rotation of the ethyl group relative to the plane of the thiazole ring, ∠(S-C2-C6-C7), is -98.6(10)° within the isolated 2-ethylthiazole molecule. Analysis of molecular geometries and non-covalent interactions reveals each hydrate complex contains a non-linear primary, N⋅⋅⋅Hb-O, hydrogen bond between an O-H of H2O and the nitrogen atom while the O atom of the water molecule(s) interacts weakly with the ethyl group. The ∠(Hb⋅⋅⋅N-C2) parameter, which defines the position of the H2O molecule relative to the thiazole ring, is found to be significantly greater for 2-ethylthiazole⋅⋅⋅H2O than for thiazole⋅⋅⋅H2O. The distance between the O atoms is determined to be 2.894(21) Å within the dihydrate complex which is shorter than observed within the isolated water dimer. The primary hydrogen bond within 2-ethylthiazole⋅⋅⋅(H2O)2 is shorter and stronger than that in 2-ethylthiazole⋅⋅⋅H2O as a result of cooperative hydrogen bonding effects.
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Affiliation(s)
- Charlotte N Cummings
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Bedson, Building, NE1 7RU, U.K
| | - Nicholas R Walker
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Bedson, Building, NE1 7RU, U.K
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Cummings C, Kleiner I, Walker NR. Noncovalent Interactions in the Molecular Geometries of 4-Methylthiazole···H 2O and 5-Methylthiazole···H 2O Revealed by Microwave Spectroscopy. J Phys Chem A 2023; 127:8133-8145. [PMID: 37751499 PMCID: PMC10561259 DOI: 10.1021/acs.jpca.3c05360] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 09/08/2023] [Indexed: 09/28/2023]
Abstract
The pure rotational spectra of 4-methylthiazole···H2O and 5-methylthiazole···H2O were recorded by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. Each complex was generated within the rotationally cold environment of a gas sample undergoing supersonic expansion in the presence of an argon buffer gas. The spectra of five isotopologues of each complex have been measured and analyzed to determine the rotational constants, A0, B0, and C0; centrifugal distortion constants, DJ, DJK, and d1; nuclear quadrupole coupling constants, χaa(N3) and [χbb(N3) - χcc(N3)]; and parameters describing the internal rotation of the CH3 group, V3 and ∠(i,b). The experimentally deduced parameters were obtained using the XIAM and the BELGI-Cs-hyperfine code. For each complex, parameters in the molecular geometry are fitted to experimentally determined moments of inertia. DFT calculations have been performed at the ωB97X-D/aug-cc-pVQZ level in support of the experiments. Each complex contains two hydrogen bonds; a comparatively strong, primary interaction between the N of thiazole and an O-H of H2O, and a weaker, secondary interaction between O and either the hydrogen atom attached to C2 (in 5-methylthiazole···H2O) or the CH3 group attached to C4 (in 4-methylthiazole···H2O). The barrier to internal rotation of the CH3 group, V3, is slightly lower for 4-methylthiazole···H2O (XIAM result is 340.05(56) cm-1) than that for the 4-methylthiazole monomer (357.6 cm-1). This is likely to be a result of internal charge redistribution within the 4-methylthiazole subunit following its coordination by H2O. At the precision of the experiments, V3 of 5-methylthiazole···H2O (XIAM result is 325.16(38) cm-1) is not significantly different from V3 of the 5-methylthiazole monomer (332.0 cm-1).
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Affiliation(s)
- Charlotte
N. Cummings
- Chemistry-
School of Natural and Environmental Sciences, Newcastle University, Bedson
Building, Newcastle-upon-Tyne, NE1 7RU, U.K.
| | - Isabelle Kleiner
- Université
de Paris and Université Paris Est Creteil, CNRS, LISA, F-75013 Paris, France
| | - Nicholas R. Walker
- Chemistry-
School of Natural and Environmental Sciences, Newcastle University, Bedson
Building, Newcastle-upon-Tyne, NE1 7RU, U.K.
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Gougoula E, Cummings CN, Xu Y, Lu T, Feng G, Walker NR. Cooperative hydrogen bonding in thiazole⋯(H 2O) 2 revealed by microwave spectroscopy. J Chem Phys 2023; 158:114307. [PMID: 36948828 DOI: 10.1063/5.0143024] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023] Open
Abstract
Two isomers of a complex formed between thiazole and two water molecules, thi⋯(H2O)2, have been identified through Fourier transform microwave spectroscopy between 7.0 and 18.5 GHz. The complex was generated by the co-expansion of a gas sample containing trace amounts of thiazole and water in an inert buffer gas. For each isomer, rotational constants, A0, B0, and C0; centrifugal distortion constants, DJ, DJK, d1, and d2; and nuclear quadrupole coupling constants, χaa(N) and [χbb(N) - χcc(N)], have been determined through fitting of a rotational Hamiltonian to the frequencies of observed transitions. The molecular geometry, energy, and components of the dipole moment of each isomer have been calculated using Density Functional Theory (DFT). The experimental results for four isotopologues of isomer I allow for accurate determinations of atomic coordinates of oxygen atoms by r0 and rs methods. Isomer II has been assigned as the carrier of an observed spectrum on the basis of very good agreement between DFT-calculated results and a set of spectroscopic parameters (including A0, B0, and C0 rotational constants) determined by fitting to measured transition frequencies. Non-covalent interaction and natural bond orbital analyses reveal that two strong hydrogen bonding interactions are present within each of the identified isomers of thi⋯(H2O)2. The first of these binds H2O to the nitrogen of thiazole (OH⋯N), and the second binds the two water molecules (OH⋯O). A third, weaker interaction binds the H2O sub-unit to the hydrogen atom that is attached to C2 (for isomer I) or C4 (for isomer II) of the thiazole ring (CH⋯O).
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Affiliation(s)
- Eva Gougoula
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Bedson Building, Newcastle-upon-Tyne NE1 7RU, United Kingdom
| | - Charlotte N Cummings
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Bedson Building, Newcastle-upon-Tyne NE1 7RU, United Kingdom
| | - Yugao Xu
- School of Chemistry and Chemical Engineering, Chongqing University, Daxuecheng South Rd. 55, 401331 Chongqing, China
| | - Tao Lu
- School of Biology and Engineering (School of Modern Industry for Health and Medicine), Guiyang 550025, China
| | - Gang Feng
- School of Chemistry and Chemical Engineering, Chongqing University, Daxuecheng South Rd. 55, 401331 Chongqing, China
| | - Nicholas R Walker
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Bedson Building, Newcastle-upon-Tyne NE1 7RU, United Kingdom
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