1
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Brito ALB, Roque JP, Sıdır İ, Fausto R. Low-Temperature Infrared Spectra and Ultraviolet-Induced Rotamerization of 5-Chlorosalicylaldehyde. J Phys Chem A 2022; 126:5148-5159. [PMID: 35905487 PMCID: PMC9778744 DOI: 10.1021/acs.jpca.2c03685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
5-Chlorosalicylaldehyde (abbreviated as 5CSA) is an important chemical used in the synthesis of fragrances, dyes, and pharmaceuticals. In this investigation, 5CSA isolated in solid N2, at 10 K, and in its neat amorphous and crystalline phases, at 50 and 190 K, respectively, were investigated by infrared spectroscopy and DFT(B3LYP)/6-311++G(d,p) calculations. The systematic theoretical analysis of the 5CSA conformational landscape showed that the compound exhibits four different conformers, which were structurally characterized in detail. In the as-deposited low-temperature matrices of 5CSA, only the most stable conformer, the intramolecularly hydrogen-bonded form I, was found. The same was observed in the case of the investigated low-temperature amorphous and crystalline phases of 5CSA. Conformer I was successfully converted into a higher-energy conformer(II), where both aldehyde and hydroxyl groups are rotated by 180° relative to their position in the initial conformer, through narrowband ultraviolet (UV) (λ = 308 nm) in situ irradiation of the as-deposited N2 matrix of 5CSA. The infrared spectra of both matrix-isolated conformers, as well as those of the neat amorphous and crystalline phases of 5CSA, were assigned and interpreted in comparative terms, allowing us to elucidate structurally and vibrationally relevant effects of the main intra- and intermolecular interactions operating in the different studied phases. Very interestingly, the observed UV-induced I → II rotamerization was found to take place in an exclusive basis, with no other photochemical processes being observed to occur upon UV irradiation, under the experimental conditions used in the present investigation.
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Affiliation(s)
- Anna Luiza B. Brito
- CQC-IMS,
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal,
| | - José P.
L. Roque
- CQC-IMS,
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - İsa Sıdır
- CQC-IMS,
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal,Department
of Physics, Bitlis Eren University, 13000 Bitlis, Turkey
| | - Rui Fausto
- CQC-IMS,
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
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2
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Roque JPL, Nunes CM, Fausto R. Matrix Isolation in Heterocyclic Chemistry. HETEROCYCLES 2022. [DOI: 10.1002/9783527832002.ch12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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3
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Fausto R, Ildiz GO, Nunes CM. IR-induced and tunneling reactions in cryogenic matrices: the (incomplete) story of a successful endeavor. Chem Soc Rev 2022; 51:2853-2872. [PMID: 35302145 DOI: 10.1039/d1cs01026c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In this article, IR-induced and tunneling-driven reactions observed in cryogenic matrices are described in a historical perspective, the entangling of the two types of processes being highlighted. The story of this still ongoing fascinating scientific endeavor is presented here following closely our own involvement in the field for more than 30 years, and thus focuses mostly on our work. It is, because of this reason, also an incomplete story. Nevertheless, it considers a large range of examples, from very selective IR-induced conformational isomerizations to IR-induced bond-breaking/bond-forming reactions and successful observations of rare heavy atom tunneling processes. As a whole, this article provides a rather general overview of the major progress achieved in the field.
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Affiliation(s)
- Rui Fausto
- CQC-IMS, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.
| | - Gulce O Ildiz
- CQC-IMS, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal. .,Department of Physics, Faculty of Sciences and Letters, Istanbul Kultur University, 34158 Bakirkoy, Istanbul, Turkey
| | - Cláudio M Nunes
- CQC-IMS, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.
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4
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M Nunes C, Pereira NAM, Viegas LP, Pinho E Melo TMVD, Fausto R. Inducing molecular reactions by selective vibrational excitation of a remote antenna with near-infrared light. Chem Commun (Camb) 2021; 57:9570-9573. [PMID: 34546241 DOI: 10.1039/d1cc03574f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate here that selective vibrational excitation of a moiety, remotely attached in relation to the molecular reaction site, might offer a generalized strategy for inducing bond-breaking/bond-forming reactions with exquisite precision. As a proof-of-principle, the electrocyclic ring-expansion of a benzazirine to a ketenimine was induced, in a cryogenic matrix, by near-IR light tuned at the overtone stretching frequency of its OH remote antenna. This accomplishment paves the way for harnessing IR vibrational excitation as a tool to guide a variety of molecular structure manipulations in an exceptional highly-selective manner.
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Affiliation(s)
- Cláudio M Nunes
- University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal.
| | - Nelson A M Pereira
- University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal.
| | - Luís P Viegas
- University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal.
| | | | - Rui Fausto
- University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal.
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5
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Lopes Jesus AJ, Rosado MTS, Fausto R, Reva I. UV-induced radical formation and isomerization of 4-methoxyindole and 5-methoxyindole. Phys Chem Chem Phys 2020; 22:22943-22955. [PMID: 33026378 DOI: 10.1039/d0cp04354k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Monomers of 4-methoxyindole and 5-methoxyindole trapped in low-temperature xenon matrices (15-16 K) were characterized by IR spectroscopy, in separate experiments. Each compound was shown to adopt the most stable 1H-tautomeric form. The photochemistry of the matrix-isolated compounds was then investigated by exciting the matrices with narrowband UV light with λ ≤ 305 nm. Two main photoproducts, similar for each compound, have been detected: (1) 4-methoxy- or 5-methoxy-indolyl radical, resulting from cleavage of the N-H bond; (2) 3H-tautomers (4-methoxy- or 5-methoxy-) with the released hydrogen atom reconnected at the C3 ring carbon atom. The presence of the two types of photoproducts in the UV-irradiated matrices was confirmed by comparison of their B3LYP/6-311++G(d,p) calculated IR spectra with the experimental spectra emerging upon the irradiations. The mechanism of the observed phototransformations was elucidated by Natural Bond Orbital and Natural Resonance Theory computations on the methoxy-substituted indolyl radicals resulting from the N-H bond cleavage. The highest natural atomic spin densities were predicted at the C3 and N1 positions of the indolyl ring, corresponding to a predominance of the resonance structures with the radical centres located at these two atoms. As a whole, the obtained experimental and theoretical data allowed establishing a general pattern for the photochemistry of methoxyindoles under matrix-isolation conditions.
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Affiliation(s)
- A J Lopes Jesus
- University of Coimbra, CQC, Department of Chemistry, 3004-535, Coimbra, Portugal.
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6
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Nunes CM, Pereira NAM, Reva I, Amado PSM, Cristiano MLS, Fausto R. Bond-Breaking/Bond-Forming Reactions by Vibrational Excitation: Infrared-Induced Bidirectional Tautomerization of Matrix-Isolated Thiotropolone. J Phys Chem Lett 2020; 11:8034-8039. [PMID: 32869645 DOI: 10.1021/acs.jpclett.0c02272] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Infrared vibrational excitation is a promising approach for gaining exceptional control of chemical reactions, in ways that cannot be attained via thermal or electronic excitation. Here, we report an unprecedented example of a bond-breaking/bond-forming reaction by vibrational excitation under matrix isolation conditions. Thiotropolone monomers were isolated in cryogenic argon matrices and characterized by infrared spectroscopy and vibrational computations (harmonic and anharmonic). Narrowband near-infrared irradiations tuned at frequencies of first CH stretching overtone (5940 cm-1) or combination modes (5980 cm-1) of the OH tautomer, the sole form of the compound that exists in the as-deposited matrices, led to its conversion into the SH tautomer. The tautomerization in the reverse direction was achieved by vibrational excitation of the SH tautomer with irradiation at 5947 or 5994 cm-1, corresponding to the frequencies of its CH stretching combination and overtone modes. This pioneer demonstration of bidirectional hydroxyl ↔ thiol tautomerization controlled by vibrational excitation creates prospects for new advances in vibrationally induced chemistry.
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Affiliation(s)
- Cláudio M Nunes
- University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal
| | - Nelson A M Pereira
- University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal
| | - Igor Reva
- University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal
| | - Patrícia S M Amado
- Centre of Marine Sciences, CCMAR, and Department of Chemistry and Pharmacy, University of Algarve, 8005-139 Faro, Portugal
| | - Maria L S Cristiano
- Centre of Marine Sciences, CCMAR, and Department of Chemistry and Pharmacy, University of Algarve, 8005-139 Faro, Portugal
| | - Rui Fausto
- University of Coimbra, CQC, Department of Chemistry, 3004-535 Coimbra, Portugal
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7
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Nunes CM, Reva I, Fausto R. Conformational isomerizations triggered by vibrational excitation of second stretching overtones. Phys Chem Chem Phys 2019; 21:24993-25001. [PMID: 31710324 DOI: 10.1039/c9cp05070a] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Vibrational excitation using frequency-tunable IR laser light has been developed as a powerful tool for selective manipulation of molecular conformations. In this methodology, vibrational excitation has been typically applied to the first stretching overtones (∼80 kJ mol-1) but also to the fundamental modes (∼40 kJ mol-1). Here, we demonstrate that selective conformational isomerizations are also achieved using excitation to second stretching overtones (∼120 kJ mol-1). The extremely weak absorptions of the second stretching overtones of molecules isolated in low-temperature matrices were measured for the first time; here using three prototype molecules: hydroxyacetone (HA), glycolic acid (GAc) and glycolamide (GAm). Benchmarking of computed anharmonic IR spectra showed that the B3LYP/SNSD method provides the best agreement with experimental frequencies of the ν(OH), 2ν(OH) and 3ν(OH) modes for the studied molecules in argon matrices. Selective irradiation at the 3ν(OH) frequencies (9850-10 500 cm-1) of HA, GAc and GAm monomers in argon matrices at 15 K successfully triggers their conformational isomerization. These results open the door to extend control over conformations separated by higher barriers and to induce other transformations not energetically accessible by excitation to the fundamental or first stretching overtone modes.
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Affiliation(s)
- Cláudio M Nunes
- CQC, Department of Chemistry, University of Coimbra, 3004-535, Coimbra, Portugal.
| | - Igor Reva
- CQC, Department of Chemistry, University of Coimbra, 3004-535, Coimbra, Portugal.
| | - Rui Fausto
- CQC, Department of Chemistry, University of Coimbra, 3004-535, Coimbra, Portugal.
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8
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Lopes Jesus AJ, Nunes CM, Reva I, Pinto SMV, Fausto R. Effects of Entangled IR Radiation and Tunneling on the Conformational Interconversion of 2-Cyanophenol. J Phys Chem A 2019; 123:4396-4405. [DOI: 10.1021/acs.jpca.9b01382] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- A. J. Lopes Jesus
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
- CQC, Faculty of Pharmacy, University of Coimbra, 3004-295 Coimbra, Portugal
| | - Cláudio M. Nunes
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - I. Reva
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Sandra M. V. Pinto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
- Scuola Normale Superiore, Piazza dei Cavalieri, 7, I-56124 Pisa, Italy
| | - R. Fausto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
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9
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Lapinski L, Reva I, Rostkowska H, Lopes Jesus AJ, Vieira Pinto SM, Fausto R, Nowak MJ. Conformational Isomerizations by Rotation around C–C or C–N Bonds: A Comparative Study on Matrix-Isolated Glycolamide and N-Hydroxyurea Excited with Near-IR Laser Light. J Phys Chem A 2019; 123:3831-3839. [DOI: 10.1021/acs.jpca.9b01992] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Leszek Lapinski
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Igor Reva
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Hanna Rostkowska
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
| | - A. J. Lopes Jesus
- CQC, Faculty of Pharmacy, University of Coimbra, 3004-295 Coimbra, Portugal
| | - Sandra M. Vieira Pinto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
- Scuola Normale Superiore, Piazza dei Cavalieri, 7, I-56124 Pisa, Italy
| | - Rui Fausto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Maciej J. Nowak
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
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10
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Góbi S, Reva I, Csonka IP, M. Nunes C, Tarczay G, Fausto R. Selective conformational control by excitation of NH imino vibrational antennas. Phys Chem Chem Phys 2019; 21:24935-24949. [DOI: 10.1039/c9cp05370k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We provide experimental evidence for the occurrence of selective and reversible conformational control over the SH group by vibrational excitation of remote NH groups. Using an imino group that acts as a molecular antenna has no precedents.
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Affiliation(s)
- Sándor Góbi
- CQC
- Department of Chemistry
- University of Coimbra
- Coimbra
- Portugal
| | - Igor Reva
- CQC
- Department of Chemistry
- University of Coimbra
- Coimbra
- Portugal
| | - István Pál Csonka
- MTA-ELTE Lendület Laboratory Astrochemistry Research Group
- Institute of Chemistry
- ELTE Eötvös Loránd University
- H–1518 Budapest
- Hungary
| | | | - György Tarczay
- MTA-ELTE Lendület Laboratory Astrochemistry Research Group
- Institute of Chemistry
- ELTE Eötvös Loránd University
- H–1518 Budapest
- Hungary
| | - Rui Fausto
- CQC
- Department of Chemistry
- University of Coimbra
- Coimbra
- Portugal
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11
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Brás EM, Fausto R. An insight into methimazole phototautomerism: Central role of the thiyl radical and effect of benzo substitution. J Mol Struct 2018. [DOI: 10.1016/j.molstruc.2018.02.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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12
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Lopes Jesus AJ, M. Nunes C, Fausto R, Reva I. Conformational control over an aldehyde fragment by selective vibrational excitation of interchangeable remote antennas. Chem Commun (Camb) 2018; 54:4778-4781. [DOI: 10.1039/c8cc01052h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We apply vibrational antennas (OH or NH2 group) to achieve unprecedented conformational control over the heavy aldehyde fragment in 2-formyl-2H-azirine, using selective vibrational excitations of the OH or NH2 stretching overtones and combination modes.
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Affiliation(s)
| | | | - Rui Fausto
- CQC
- Department of Chemistry
- University of Coimbra
- Coimbra
- Portugal
| | - Igor Reva
- CQC
- Department of Chemistry
- University of Coimbra
- Coimbra
- Portugal
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13
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Reva I, Lapinski L, Lopes Jesus AJ, Nowak MJ. Photoinduced transformations of indole and 3-formylindole monomers isolated in low-temperature matrices. J Chem Phys 2017; 147:194304. [DOI: 10.1063/1.5003326] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Igor Reva
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Leszek Lapinski
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
| | - A. J. Lopes Jesus
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
- CQC, Faculty of Pharmacy, University of Coimbra, 3004-295 Coimbra, Portugal
| | - Maciej J. Nowak
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
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14
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Ryazantsev SV, Feldman VI, Khriachtchev L. Conformational Switching of HOCO Radical: Selective Vibrational Excitation and Hydrogen-Atom Tunneling. J Am Chem Soc 2017. [DOI: 10.1021/jacs.7b02605] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sergey V. Ryazantsev
- Department
of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia
- Department
of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FIN-00014, Finland
| | - Vladimir I. Feldman
- Department
of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Leonid Khriachtchev
- Department
of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FIN-00014, Finland
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15
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Kovács B, Kuş N, Tarczay G, Fausto R. Experimental Evidence of Long-Range Intramolecular Vibrational Energy Redistribution through Eight Covalent Bonds: NIR Irradiation Induced Conformational Transformation of E-Glutaconic Acid. J Phys Chem A 2017; 121:3392-3400. [PMID: 28423274 DOI: 10.1021/acs.jpca.7b00615] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Long-range intramolecular vibrational energy redistribution (IVR) driven conformational changes were investigated in a matrix-isolated open-chain, asymmetrical dicarboxylic acid, E-glutaconic acid. Although the analysis was challenging due to the presence of multiple backbone conformers and short lifetimes of the prepared higher energy cis conformers, it was shown that the selective excitation of the O-H stretching overtone of one of the carboxylic groups can induce the conformational change (trans to cis) of the other carboxylic group, located at the other end of the E-glutaconic acid molecule. This is a direct proof that the IVR process can act through eight covalent bonds in a flexible molecule before the excess energy completely dissipates into the matrix. The lifetime of the prepared higher energy conformers (averaged over the different backbones) was measured to be 12 s.
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Affiliation(s)
- Benjámin Kovács
- Institute of Chemistry, Eötvös University , PO Box 32, H-1518 Budapest 112, Hungary
| | - Nihal Kuş
- CQC, Department of Chemistry, University of Coimbra , 3004-535 Coimbra, Portugal.,Department of Physics, Anadolu University , TR-26470 Eskişehir, Turkey
| | - György Tarczay
- Institute of Chemistry, Eötvös University , PO Box 32, H-1518 Budapest 112, Hungary
| | - Rui Fausto
- CQC, Department of Chemistry, University of Coimbra , 3004-535 Coimbra, Portugal
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16
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Lopes Jesus AJ, Fausto R, Reva I. Conformational Changes in 5-Methoxyindole: Effects of Thermal, Vibrational, and Electronic Excitations. J Phys Chem A 2017; 121:3372-3382. [DOI: 10.1021/acs.jpca.7b01713] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. J. Lopes Jesus
- CQC,
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
- CQC,
Faculty of Pharmacy, University of Coimbra, 3004-295 Coimbra, Portugal
| | - R. Fausto
- CQC,
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - I. Reva
- CQC,
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
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17
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Kuş N, Fausto R. Effects of the matrix and intramolecular interactions on the stability of the higher-energy conformers of 2-fluorobenzoic acid. J Chem Phys 2017; 146:124305. [DOI: 10.1063/1.4978794] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Lopes Jesus A, Reva I, Fausto R. UV-induced transformations in matrix-isolated 6‐methoxyindole. J Photochem Photobiol A Chem 2017. [DOI: 10.1016/j.jphotochem.2016.12.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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19
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Justino LLG, Reva I, Fausto R. Thermally and vibrationally induced conformational isomerizations, infrared spectra, and photochemistry of gallic acid in low-temperature matrices. J Chem Phys 2017; 145:014304. [PMID: 27394105 DOI: 10.1063/1.4954894] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Near-infrared (near-IR) narrowband selective vibrational excitation and annealing of gallic acid (3,4,5-trihydroxybenzoic acid) isolated in cryogenic matrices were used to induce interconversions between its most stable conformers. The isomerizations were probed by infrared spectroscopy. An extensive set of quantum chemical calculations, carried out at the DFT(B3LYP)/6-311++G(d,p) level of approximation, was used to undertake a detailed analysis of the ground state potential energy surface of the molecule. This investigation of the molecule conformational space allowed extracting mechanistic insights into the observed annealing- or near-IR-induced isomerization processes. The infrared spectra of the two most stable conformers of gallic acid in N2, Xe, and Ar matrices were fully assigned. Finally, the UV-induced photochemistry of the matrix isolated compound was investigated.
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Affiliation(s)
- Licínia L G Justino
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Igor Reva
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Rui Fausto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
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20
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Halasa A, Reva I, Lapinski L, Rostkowska H, Fausto R, Nowak MJ. Conformers of Kojic Acid and Their Near-IR-Induced Conversions: Long-Range Intramolecular Vibrational Energy Transfer. J Phys Chem A 2016; 120:2647-56. [DOI: 10.1021/acs.jpca.6b01275] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anna Halasa
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Igor Reva
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Leszek Lapinski
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Hanna Rostkowska
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Rui Fausto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Maciej J. Nowak
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland
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21
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Lopes Jesus AJ, Reva I, Araujo-Andrade C, Fausto R. Conformational changes in matrix-isolated 6-methoxyindole: Effects of the thermal and infrared light excitations. J Chem Phys 2016; 144:124306. [PMID: 27036447 DOI: 10.1063/1.4944528] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Conformational changes induced thermally or upon infrared excitation of matrix-isolated 6-methoxyindole were investigated. Narrowband near-infrared excitation of the first overtone of the N-H stretching vibration of each one of the two identified conformers is found to induce a selective large-scale conversion of the pumped conformer into the other one. This easily controllable bidirectional process consists in the intramolecular reorientation of the methoxy group and allowed a full assignment of the infrared spectra of the two conformers. Matrices with different conformational compositions prepared by narrow-band irradiations were subsequently used to investigate the effects of both thermal and broadband infrared excitations on the conformational mixtures. Particular attention is given to the influence of the matrix medium (Ar vs. Xe) and conformational effects of exposition of the sample to the spectrometer light source during the measurements.
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Affiliation(s)
- A J Lopes Jesus
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - I Reva
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - C Araujo-Andrade
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - R Fausto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
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