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Ventura E, Rodrigues GP, Leitão EFV, do Monte SA. Theoretical Study of an Authentic Hydrocarbon Ion Pair. ACS OMEGA 2024; 9:34981-34989. [PMID: 39157103 PMCID: PMC11325399 DOI: 10.1021/acsomega.4c04914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2024] [Revised: 07/17/2024] [Accepted: 07/22/2024] [Indexed: 08/20/2024]
Abstract
For many years researchers believed that hydrocarbons only contain covalent bonds. However, since 1985 Okamoto et al. demonstrated the formation of hydrocarbon salts in several systems, demolishing the structural principle that hydrocarbons only contain covalent bonds. Despite the great importance of this outcome to the study of chemical bonds, quantum chemical calculations on these systems are essentially nonexistent. The stability of the hydrocarbon ions along with the steric hindrance associated with the formation of the covalent bond contribute to their occurrence either in solution (dissociated) or in the solid state. These facts along with the common formation of ion pairs in solvents of low polarity motivated us to search for hydrocarbon ion pairs in the gas phase. Its energetics has also been studied in four nonprotic solvents, through a continuum solvation model (CPCM). DFT and CASSCF calculations indicate a metastable and highly polar ion pair between the tricyclopropylcyclopropenylium cation and a simplified Kuhn's anion. The barrier to the covalent structure varies from ∼4.8 to 14.4 kcal/mol, while the energy difference between the ion pair and the covalent form varies from ∼4.3 to 25.4 kcal/mol. The obtained theoretical results along with previous experimental results suggest the following strategy to obtain kinetically and thermodynamically stable hydrocarbon ion pairs: choose very stable hydrocarbon ions and systematically increase the steric hindrance between them.
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Affiliation(s)
- Elizete Ventura
- Departamento
de Química, CCEN, Universidade Federal
da Paraíba, 58059-900 João Pessoa, Brazil
| | | | - Ezequiel Fragoso Vieira Leitão
- Unidade
Acadêmica de Ciências Exatas e da Natureza, Universidade Federal de Campina Grande, Cajazeiras, PB 58900-000, Brazil
| | - Silmar Andrade do Monte
- Departamento
de Química, CCEN, Universidade Federal
da Paraíba, 58059-900 João Pessoa, Brazil
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Albertini S, Gruber E, Zappa F, Krasnokutski S, Laimer F, Scheier P. Chemistry and physics of dopants embedded in helium droplets. MASS SPECTROMETRY REVIEWS 2022; 41:529-567. [PMID: 33993543 DOI: 10.1002/mas.21699] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/20/2021] [Accepted: 04/20/2021] [Indexed: 05/18/2023]
Abstract
Helium droplets represent a cold inert matrix, free of walls with outstanding properties to grow complexes and clusters at conditions that are perfect to simulate cold and dense regions of the interstellar medium. At sub-Kelvin temperatures, barrierless reactions triggered by radicals or ions have been observed and studied by optical spectroscopy and mass spectrometry. The present review summarizes developments of experimental techniques and methods and recent results they enabled.
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Affiliation(s)
- Simon Albertini
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Elisabeth Gruber
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Fabio Zappa
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Serge Krasnokutski
- Laboratory Astrophysics Group of the MPI for Astronomy, University of Jena, Jena, Germany
| | - Felix Laimer
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
| | - Paul Scheier
- Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, Austria
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Araújo JR, de Andrade RB, Batista HJ, Ventura E, do Monte SA. Can a gas phase contact ion pair containing a hydrocarbon carbocation be formed in the ground state? RSC Adv 2021; 11:4221-4230. [PMID: 35424376 PMCID: PMC8694316 DOI: 10.1039/d0ra10523f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 01/11/2021] [Indexed: 11/21/2022] Open
Abstract
So far, no conclusive evidence of a ground-state contact ion-pair containing a hydrocarbon carbocation has been given in the gas phase.
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Affiliation(s)
- José R. Araújo
- Departamento de Química
- CCEN
- Universidade Federal da Paraíba
- João Pessoa
- Brazil
| | | | - Hélcio J. Batista
- Departamento de Química
- Universidade Federal Rural de Pernambuco
- Recife
- Brazil
| | - Elizete Ventura
- Departamento de Química
- CCEN
- Universidade Federal da Paraíba
- João Pessoa
- Brazil
| | - Silmar A. do Monte
- Departamento de Química
- CCEN
- Universidade Federal da Paraíba
- João Pessoa
- Brazil
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Brice JT, Liang T, Raston PL, McCoy AB, Douberly GE. Infrared Stark and Zeeman spectroscopy of OH–CO: The entrance channel complex along the OH + CO → trans-HOCO reaction pathway. J Chem Phys 2016; 145:124310. [DOI: 10.1063/1.4963226] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Joseph T. Brice
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA
| | - Tao Liang
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA
| | - Paul L. Raston
- Department of Chemistry and Biochemistry, James Madison University, Harrisonburg, Virginia 22807, USA
| | - Anne B. McCoy
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Gary E. Douberly
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA
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Zhang C, Zhang Z, Huang C, Zhang Q, Chen Y. Helium Droplets: An Apparatus to Study Ultra Cold Chemistry. CHINESE J CHEM PHYS 2013. [DOI: 10.1063/1674-0068/26/03/270-276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Krasnokutski SA, Huisken F. Ultra-Low-Temperature Reactions of Mg Atoms with O2 Molecules in Helium Droplets. J Phys Chem A 2010; 114:7292-300. [DOI: 10.1021/jp103947z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Serge A. Krasnokutski
- Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Helmholtzweg 3, D-07743 Jena, Germany
| | - Friedrich Huisken
- Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena, Helmholtzweg 3, D-07743 Jena, Germany
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Merritt JM, Douberly GE, Stiles PL, Miller RE. Infrared Spectroscopy of Prereactive Aluminum−, Gallium−, and Indium−HCN Entrance Channel Complexes Solvated in Helium Nanodroplets. J Phys Chem A 2007; 111:12304-16. [PMID: 17877336 DOI: 10.1021/jp074981e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Prereactive metal atom-HCN entrance channel complexes [M-HCN (M=Al, Ga, In)] have been stabilized in helium nanodroplets. Rotationally resolved infrared spectra are reported for the CH stretching vibration of the linear nitrogen-bound HCN-Ga and HCN-In complexes that show significant perturbation due to spin-orbit coupling of the 2Pi1/2 ground state with the 2Sigma1/2 state which are degenerate at long range. Six unresolved bands are also observed and assigned to the linear hydrogen-bound isomers of Al-HCN, Ga-HCN, and In-HCN corresponding to the fundamental CH stretching vibration and a combination band involving the CH stretch plus intermolecular stretch for each isomer. A nitrogen-bound HCN-Al complex is not observed, which is attributed to reaction, even at 0.37 K. This conclusion is supported by the observation of a weakly bound complex containing two HCN's and one Al atom which, from the analysis of its rotationally resolved zero-field and Stark spectra is assigned to a weakly bound complex of a HCNAl reaction product and a second HCN molecule. Theoretical calculations are presented to elucidate the reaction mechanisms and energetics of these metal atom reactions with HCN.
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Affiliation(s)
- Jeremy M Merritt
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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Fishchuk AV, Merritt JM, van der Avoird A. Ab Initio Treatment of the Chemical Reaction Precursor Complex Br( 2P)−HCN. 1. Adiabatic and Diabatic Potential Surfaces. J Phys Chem A 2007; 111:7262-9. [PMID: 17567108 DOI: 10.1021/jp068495n] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The three adiabatic potential surfaces of the Br(2P)-HCN complex that correlate to the 2P ground state of the Br atom were calculated ab initio. With the aid of a geometry-dependent diabatic mixing angle, also calculated ab initio, these adiabatic potential surfaces were transformed into a set of four diabatic potential surfaces required to define the full 3 x 3 matrix of diabatic potentials. Each of these diabatic potential surfaces was expanded in terms of the appropriate spherical harmonics in the atom-linear molecule Jacobi angle theta. The dependence of the expansion coefficients on the distance R between Br and the HCN center of mass and on the CH bond length was fit to an analytic form. For HCN in its equilibrium geometry, the global minimum with De = 800.4 cm(-1) and Re = 6.908a0 corresponds to a linear Br-NCH geometry, with an electronic ground state of Sigma symmetry. A local minimum with De = 415.1 cm-1, Re = 8.730a0, and a twofold degenerate Pi ground state is found for the linear Br-HCN geometry. The binding energy, De, depends strongly on the CH bond length for the Br-HCN complex and much less strongly for the Br-NCH complex, with a longer CH bond giving stronger binding for both complexes. Spin-orbit coupling was included and diabatic states were constructed that correlate to the ground 2P3/2 and excited 2P1/2 spin-orbit states of the Br atom. For the ground spin-orbit state with electronic angular momentum j = (3/2) the minimum in the potential for projection quantum number omega = +/-(3/2) coincides with the local minimum for linear Br-HCN of the spin-free case. The minimum in the potential for projection quantum number omega = +/-(1/2) occurs for linear Br-NCH but is considerably less deep than the global minimum of the spin-free case. According to the lowest spin-orbit coupling included adiabatic potential the two linear isomers, Br-NCH and Br-HCN, are about equally stable. In the subsequent paper, we use these potentials in calculations of the rovibronic states of the Br-HCN complex.
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Affiliation(s)
- Anna V Fishchuk
- Theoretical Chemistry, IMM, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
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Fishchuk AV, Merritt JM, Groenenboom GC, Avoird AVD. Ab Initio Treatment of the Chemical Reaction Precursor Complex Br(2P)−HCN. 2. Bound-State Calculations and Infrared Spectra. J Phys Chem A 2007; 111:7270-81. [PMID: 17567109 DOI: 10.1021/jp0684978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rovibronic energy levels and properties of the Br(2P)-HCN complex were obtained from three-dimensional calculations, with HCN kept linear and the CN bond frozen. All diabatic states that correlate to the 2P3/2 and 2P1/2 states of the Br atom were included and spin-orbit coupling was taken into account. The 3 x 3 matrix of diabatic potential surfaces was taken from the preceding paper (paper 1). In agreement with experiment, we found two linear isomers, Br-NCH and Br-HCN. The calculated binding energies are very similar: D0 = 352.4 cm(-1) and D0 = 349.1 cm(-1), respectively. We established, also in agreement with experiment, that the ground electronic state of Br-NCH has |Omega| = (1/2) and that Br-HCN has a ground state with |Omega| = (3/2), where the quantum number, Omega, is the projection of the total angular momentum, J, of the complex on the intermolecular axis R. This picture can be understood as being caused by the electrostatic interaction between the quadrupole of the Br(2P) atom and the dipole of HCN, combined with the very strong spin-orbit coupling in Br. We predicted the frequencies of the van der Waals modes of both isomers and found a direct Renner-Teller splitting of the bend mode in Br-HCN and a smaller, indirect, splitting in Br-NCH. The red shift of the CH stretch frequency in the complex, relative to free HCN, was calculated to be 1.98 cm(-1) for Br-NCH and 23.11 cm(-1) for Br-HCN, in good agreement with the values measured in helium nanodroplets. Finally, with the use of the same potential surfaces, we modeled the Cl(2P)-HCN complex and found that the experimentally observed linear Cl-NCH isomer is considerably more stable than the (not observed) Cl-HCN isomer. This was explained mainly as an effect of the substantially smaller spin-orbit coupling in Cl, relative to Br.
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Affiliation(s)
- Anna V Fishchuk
- Theoretical Chemistry, IMM, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
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Küpper J, Merritt JM. Spectroscopy of free radicals and radical containing entrance-channel complexes in superfluid helium nanodroplets. INT REV PHYS CHEM 2007. [DOI: 10.1080/01442350601087664] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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