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Roque JPL, Rosado MTS, Fausto R, Reva I. Dual Photochemistry of Benzimidazole. J Org Chem 2023; 88:2884-2897. [PMID: 36795993 PMCID: PMC9990075 DOI: 10.1021/acs.joc.2c02560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Monomers of benzimidazole trapped in an argon matrix at 15 K were characterized by vibrational spectroscopy and identified as 1H-tautomers exclusively. The photochemistry of matrix-isolated 1H-benzimidazole was induced by excitations with a frequency-tunable narrowband UV light and followed spectroscopically. Hitherto unobserved photoproducts were identified as 4H- and 6H-tautomers. Simultaneously, a family of photoproducts bearing the isocyano moiety was identified. Thereby, the photochemistry of benzimidazole was hypothesized to follow two reaction pathways: the fixed-ring and the ring-opening isomerizations. The former reaction channel results in the cleavage of the NH bond and formation of a benzimidazolyl radical and an H-atom. The latter reaction channel involves the cleavage of the five-membered ring and concomitant shift of the H-atom from the CH bond of the imidazole moiety to the neighboring NH group, leading to 2-isocyanoaniline and subsequently to the isocyanoanilinyl radical. The mechanistic analysis of the observed photochemistry suggests that detached H-atoms, in both cases, recombine with the benzimidazolyl or isocyanoanilinyl radicals, predominantly at the positions with the largest spin density (revealed using the natural bond analysis computations). The photochemistry of benzimidazole therefore occupies an intermediate position between the earlier studied prototype cases of indole and benzoxazole, which exhibit exclusively the fixed-ring and the ring-opening photochemistries, respectively.
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Affiliation(s)
- José P L Roque
- CQC-IMS, Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal
| | - Mário T S Rosado
- CQC-IMS, Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal
| | - Rui Fausto
- CQC-IMS, Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal
| | - Igor Reva
- CQC-IMS, Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal.,CIEPQPF, Department of Chemical Engineering, University of Coimbra, Coimbra 3030-790, Portugal
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Makuvaza JT, Loman JL, Kokkin DL, Reid SA. Probing cooperativity in C-H⋯N and C-H⋯π interactions: Dissociation energies of aniline⋯(CH 4) n (n = 1, 2) van der Waals complexes from resonant ionization and velocity mapped ion imaging measurements. J Chem Phys 2020; 153:044303. [PMID: 32752709 DOI: 10.1063/5.0015624] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recent studies of the weakly bound anisole⋯CH4 complex found a dual mode of binding, featuring both C/H⋯π and C/H⋯O noncovalent interactions. In this work, we examine the dissociation energies of related aniline⋯(CH4)n (n = 1, 2) van der Waals clusters, where both C/H⋯π and C/H⋯N interactions are possible. Using a combination of theory and experiments that include mass-selected two-color resonant two-photon ionization spectroscopy, two-color appearance potential (2CAP) measurements, and velocity-mapped ion imaging (VMI), we derive the dissociation energies of both complexes in the ground (S0), excited (S1), and cation radical (D0) states. As the amide group is non-planar in the ground state, the optimized ground state geometry of the aniline⋯CH4 1:1 complex shows two isomers, each with the methane positioned above the aniline ring. The observed redshift of the electronic origin from the aniline monomer is consistent with TDDFT calculations for the more stable isomer, where the methane sits on the same face as the amino hydrogens. The dissociation energies of the 1:1 complex, obtained from 2CAP measurements, are in good agreement with the calculated theoretical values from selected density functional theory methods. VMI data for the 1:1 complex gave a binding energy value overestimated by ∼179 cm-1 when compared to the 2CAP results, indicating that dissociative ionization selectively populates an excited vibrational level of the aniline cation radical. Given that the electron donating ability of aromatic substituents trends as -NH2 > -OCH3 > -CH3, it is noteworthy that the strength of methane binding also trends in this order, as found by experiment (dissociation energies in kJ/mol: 6.6 > 5.8 > 4.5) and predicted by theory (PBE0-D3/def2-QZVPPD, in kJ/mol: 6.9 > 6.0 > 5.0). For the 1:2 complex of aniline and methane, calculations predict that the more stable conformer is the one where the two methane molecules lie on opposite faces of the ring, consistent with the observed redshift of the electronic origin. Unlike the anisole-methane 1:2 complex, which shows an enhanced dissociation energy for the loss of one methane in comparison with the 1:1 complex, here, we find that the energy required to remove one methane from the ground state aniline-methane 1:2 complex is smaller than that of the 1:1 complex, consistent with theoretical expectations.
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Affiliation(s)
- James T Makuvaza
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, USA
| | - John L Loman
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, USA
| | - Damian L Kokkin
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, USA
| | - Scott A Reid
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, USA
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Roy M, Alauddin M, Song JK, Park SM. Structures of aniline(pyrrole) +, aniline(ethanol) +, and aniline-(benzene) . SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2018; 204:665-669. [PMID: 29982157 DOI: 10.1016/j.saa.2018.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 06/14/2018] [Accepted: 07/01/2018] [Indexed: 06/08/2023]
Abstract
Molecular structures of aniline(pyrrole)+, aniline(ethanol)+, and aniline(benzene)+ produced via resonance two-photon ionization at 266 nm were analyzed by infrared predissociation spectroscopy coupled with tandem mass spectrometry. Structural optimization and frequency calculation using density functional theory were carried out to suggest the most probable isomers which are in good agreement with the observed infrared absorption spectra. Intermolecular bonds in the cluster ions were formed such that the electronegative oxygen atom of the solvent molecule or the pi electron of the aromatic ring forms a hydrogen bonding to NH of aniline.
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Affiliation(s)
- Madhusudan Roy
- Department of Chemistry, Kyung Hee University, Seoul 02447, South Korea
| | - Mohammad Alauddin
- Department of Chemistry, Kyung Hee University, Seoul 02447, South Korea
| | - Jae Kyu Song
- Department of Chemistry, Kyung Hee University, Seoul 02447, South Korea
| | - Seung Min Park
- Department of Chemistry, Kyung Hee University, Seoul 02447, South Korea.
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Sarkar S, Ramanathan N, Gopi R, Sundararajan K. Pyrrole multimers and pyrrole-acetylene hydrogen bonded complexes studied in N2 and para-H2 matrixes using matrix isolation infrared spectroscopy and ab initio computations. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2017.07.110] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Yuan C, An P, Chen J, Luo Z, Yao J. Unraveling weak interactions in aniline-pyrrole dimer clusters. Sci China Chem 2016. [DOI: 10.1007/s11426-016-0105-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Chowdhury PK. Infrared depletion spectroscopy of the doubly hydrogen-bonded aniline–(tetrahydrofuran)2 complex produced in supersonic jet. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2005.06.041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Piracha N, Ito F, Nakanaga T. Infrared depletion spectroscopy of aniline–toluene cluster: the investigation of the red shifts of the NH2 stretching vibrations of aniline–aromatic clusters. Chem Phys 2004. [DOI: 10.1016/j.chemphys.2003.10.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Chowdhury PK. Infrared Depletion Spectroscopy of the Hydrogen-Bonded Aniline−Diethylamine (C6H5-NH2···NHC4H10) Complex Produced in Supersonic Jet. J Phys Chem A 2003. [DOI: 10.1021/jp034538d] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- P. K. Chowdhury
- National Institute for Advanced Interdisciplinary Research, 1-1-4 Higashi, Tsukuba, Ibaraki 305, Japan
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Honkawa Y, Inokuchi Y, Ohashi K, Nishi N, Sekiya H. Infrared spectra and structures of aniline+–furan and aniline+–phenol. Preference between π-type and σ-type hydrogen-bonded structures. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(03)00985-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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The pyrrole ring as hydrogen-bonding π-donor base: an experimental and theoretical study of the interactions of N-methylpyrrole with alcohols. Chem Phys 2003. [DOI: 10.1016/s0301-0104(03)00100-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Nakanaga T, Buchhold K, Ito F. Investigation of the NH-π hydrogen bond interaction in the aniline–alkene (C2H4,C3H6,C4H8) cluster cations by infrared depletion spectroscopy. Chem Phys 2003. [DOI: 10.1016/s0301-0104(02)01051-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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13
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Patwari G, Ebata T, Mikami N. Gas phase dihydrogen bonding: clusters of borane-amines with phenol and aniline. Chem Phys 2002. [DOI: 10.1016/s0301-0104(02)00529-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Inokuchi Y, Ohashi K, Honkawa Y, Sekiya H, Nishi N. Intracluster proton transfer in aniline–amine complex ions. Chem Phys Lett 2002. [DOI: 10.1016/s0009-2614(02)00737-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Piracha N, Nakanaga T. Infrared spectroscopy of aniline–Ne clusters and the corresponding cluster cations in the NH2-stretching vibration region. J Mol Struct 2002. [DOI: 10.1016/s0022-2860(02)00066-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Nakanaga T, Buchhold K, Ito F. Weak hydrogen bond interactions in the aniline–alkene (CH2CH(CH2)nH, n=0,1,2) clusters studied by infrared depletion spectroscopy. Chem Phys 2002. [DOI: 10.1016/s0301-0104(02)00307-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Nakanaga T, Piracha NK, Ito F. The evidence of the mode selectivity of the infrared predissociation reaction of the hydrogen bonds in the aniline–water–pyrrole cluster cation. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)00989-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Nakanaga T, Piracha NK, Ito F. Investigation of the Structure of the Ternary Cluster of Aniline−Water−Tetrahydrofuran and Its Cation by Infrared Depletion Spectroscopy. J Phys Chem A 2001. [DOI: 10.1021/jp001872q] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Taisuke Nakanaga
- National Institute of Materials and Chemical Research, Higashi 1-1-4, Tsukuba, Ibaraki 305-8565, Japan
| | - Naveed K. Piracha
- National Institute of Materials and Chemical Research, Higashi 1-1-4, Tsukuba, Ibaraki 305-8565, Japan
| | - Fumiyuki Ito
- National Institute of Materials and Chemical Research, Higashi 1-1-4, Tsukuba, Ibaraki 305-8565, Japan
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Brutschy B. The structure of microsolvated benzene derivatives and the role of aromatic substituents. Chem Rev 2000; 100:3891-920. [PMID: 11749333 DOI: 10.1021/cr990055n] [Citation(s) in RCA: 253] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- B Brutschy
- Institut für Physikalische und Theoretische Chemie, J. W. Goethe-Universität Frankfurt, Marie-Curie-Str. 11, D-60439 Frankfurt a. M., Germany
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Chowdhury PK. Infrared Depletion Spectroscopy Suggests Mode-Specific Vibrational Dynamics in the Hydrogen-Bonded Aniline−Diethyl Ether (C6H5−NH2···OC4H10) Complex. J Phys Chem A 2000. [DOI: 10.1021/jp000871v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- P. K. Chowdhury
- National Institute for Advanced Interdisciplinary Research, 1-1-4 Higashi, Tsukuba, Ibaraki 305, Japan
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Ohashi K, Inokuchi Y, Izutsu H, Hino K, Yamamoto N, Nishi N, Sekiya H. Electronic and vibrational spectra of aniline–benzene hetero-dimer and aniline homo-dimer ions. Chem Phys Lett 2000. [DOI: 10.1016/s0009-2614(00)00497-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chowdhury P. Infrared depletion spectroscopy suggests fast vibrational relaxation in the hydrogen-bonded aniline–tetrahydrofuran (C6H5–NH2⋯OC4H8) complex. Chem Phys Lett 2000. [DOI: 10.1016/s0009-2614(00)00153-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Nakanaga T, Ito F. Investigations on the Hydrogen Bond Interaction in the Aniline−Furan Complex and Its Cation by Infrared Depletion Spectroscopy. J Phys Chem A 1999. [DOI: 10.1021/jp983631c] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Taisuke Nakanaga
- National Institute of Materials and Chemical Research, Tsukuba, Ibaraki 305-8565, Japan
| | - Fumiyuki Ito
- National Institute of Materials and Chemical Research, Tsukuba, Ibaraki 305-8565, Japan
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Fujimaki E, Fujii A, Ebata T, Mikami N. Autoionization-detected infrared spectroscopy of intramolecular hydrogen bonds in aromatic cations. I. Principle and application to fluorophenol and methoxyphenol. J Chem Phys 1999. [DOI: 10.1063/1.478306] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
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