Structural transformations of 3-fluoro and 3-fluoro-4-methoxy benzaldehydes under cryogenic conditions: A computational and low temperature infrared spectroscopy investigation

Ildız, Gülce Öğrüç; Konarska, J.; Fausto, Rui

doi:10.1016/j.chemphys.2018.04.011

Cited by 4 publications

(4 citation statements)

References 27 publications

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“…The performed irradiations led to excitation to the S 2 to S 5 states and can be expected to allow for facile intersystem crossing to the triplet manifold, considering the existence of nine triplet states with energy below S 5 , where the bond cleavages leading to formation of the intermediate radical species involved in the decarbonylation of BPCA take place [ 39 ]. On the other hand, taking into account previous results for other aromatic aldehydes [ 4 , 5 , 6 , 7 , 8 , 38 ], the observed photo-induced trans → cis BPCA conformational isomerization occurs, much probably, in the singlet manifold (either in S 1 or S 0 , after internal conversion).…”

Section: Resultssupporting

confidence: 61%

“…The decarbonylation of aromatic aldehydes has been observed frequently as a result of UV irradiation of these type of compounds under matrix isolation conditions [ 6 , 7 , 8 , 38 ]. The fact that the reaction was found to be more efficient in the Xe matrix indicates stabilization of the radical species initially formed upon breaking of the C–C(HO) and C–H (aldehyde) bonds, in this medium.…”

Section: Resultsmentioning

confidence: 99%

“…From the structural point of view, BPCA appears as an interesting compound due to the following characteristics: (i) the molecule of the compound possesses an internal rotational degree of freedom (the torsion around the exocyclic C–C bond), so that different conformers can be expected to exist; (ii) the location of the aldehyde substituent at the ortho position to the pyridine nitrogen atom can be anticipated to lead to relevant conformation-dependent intramolecular interactions between these two moieties; (iii) the presence of the voluminous, strongly polarizable bromine substituent in the molecule opens expectations regarding its importance in determining fundamental characteristics of the crystal structure of the compound; (iv) the unimolecular photochemistry of the isolated molecules of the compound appears as an interesting topic to be investigated, considering the a priori possibility of occurrence of both UV-induced conformational isomerization [ 4 , 5 , 6 ] and photofragmentation reactions, specifically decarbonylation [ 6 , 7 , 8 ], pyridine ring valence isomerization [ 9 , 10 , 11 ], and Br atom extrusion [ 12 , 13 ]. The investigation of all these characteristics appears as a fundamental step for the detailed understanding of the physicochemical behavior of BPCA, bridging the properties of the isolated molecule to those of the neat crystalline compound and potentiating its use in supramolecular chemistry, in synthesis, and other practical applications, as those mentioned above.…”

Section: Introductionmentioning

confidence: 99%

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Structure, Vibrational Spectra, and Cryogenic MatrixPhotochemistry of 6-Bromopyridine-2-carbaldehyde: From the Single Molecule of the Compound to the Neat Crystalline Material

et al. 2023

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6-Bromopyridine-2-carbaldehyde (abbreviated as BPCA) is used both as a building block in supramolecular chemistry and as a ligand for transition metal catalysts and luminescent complexes. In this study, the structure and vibrational spectra of BPCA were investigated in both the room temperature neat crystalline phase and for the compound isolated in cryogenic Ar, Kr and Xe matrices. The experimental studies were complemented by quantum chemical DFT(B3LYP)/6-311++G(d,p) calculations. For the crystalline compound, infrared and Raman spectra were obtained and interpreted. Comparison of the obtained infrared spectrum of the crystal with those obtained for the isolated molecules of BPCA in the studied cryomatrices helped to conclude that the intermolecular interactions in the crystal do not significantly perturb the intramolecular vibrational potential. Structural analysis further supports the existence of weak coupling between the intermolecular interactions and the structure of the constituting molecular units in crystalline state. The intermolecular interactions in the BPCA crystal were also evaluated by means of Hirshfeld analysis, which revealed that the most important interactions are weak and of the H…N, H…O, H…H, H…Br and Br…Br types. The conformer of BPCA present in the crystal was found to correspond to the most stable form of the isolated molecule (trans), which bears stabilizing C–H…O=C and C(=O)H…N interactions. This conformer was shown to be the single conformer present in the as-deposited cryogenic matrices prepared from the room temperature gaseous compound. Broadband UV irradiation of matrix-isolated BPCA (λ ≥ 235 nm) resulted in the conversion of the trans conformer into the higher-energy cis conformer, where repulsive C–H…H–C(=O) and C=OLP…LPN (where LP designates a lone electron pair) interactions are present, and decarbonylation of the compound with formation of 2-bromopyridine (plus CO). The decarbonylation reaction was found to be more efficient in the more polarizable Xe matrix, indicating stabilization of the radicals initially formed upon breaking of the C–C(HO) and C–H (aldehyde) bonds in this medium, and testifying the occurrence of the decarbonylation reaction with involvement of radical species. TD-DFT calculations were used to access the nature of the excited states associated with the observed UV-induced reactions. As a whole, this study provides fundamental data to understand the physicochemical behavior of the compound, bridging the properties of the isolated molecule to those of the neat crystalline com-pound. Such information is of fundamental importance for the understanding of the role of BPCA in supramolecular chemistry and to potentiate its applications in synthesis and as a ligand for transition metal catalysts and luminescent complexes.

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Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure, Vibrational Spectra, and Cryogenic MatrixPhotochemistry of 6-Bromopyridine-2-carbaldehyde: From the Single Molecule of the Compound to the Neat Crystalline Material

et al. 2023

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“…The peaks in the range from 1690 to 1500 cm −1 resulted from the stretching vibrations of CC and CO bonds, while the less intense peak at 1712 cm −1 and the strong peak at 1287 cm −1 may have resulted from stretching vibrations of –SO 3 H groups 20 . The peaks at 1170 and 1008 cm −1 were likely caused by OSO groups 21 and the intense peak at 860 cm −1 was ascribed to –CH 3 O groups 22 . Together, these data indicate successful sulfonation of the carbon microspheres.…”

Section: Resultsmentioning

confidence: 98%

Oxidation reaction mechanism of hydrothermal carbon microspheres with applications to transesterification after sulfonation

Xue

Zhao

2022

J of Chemical Tech & Biotech

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Background An efficient sulfonic acid‐type acid catalyst with high acid site density based on hydrothermal carbon microspheres (HCMs) has been developed. The reaction by which double bonds in the HCMs were oxidized to generate carboxyl groups was evaluated based on density functional theory calculations. Results Sulfonic acid‐type HCMs (SHCMs) were prepared from HCMs through a three‐step process comprising oxidation, amidation and sulfonation. An analysis of the oxidation process indicated that the formation of carboxyl groups involved the activation of O2 molecules and CH bonds, the cleavage of CC bonds, the homolytic fission of peroxy acids and the coupling reactions of H• radicals. The formation of numerous carboxyl groups on the HCM surfaces was the key to obtaining SHCMs with a high acid density of 14.5 mmol g−1. Conclusions The SHCMs obtained exhibited good catalytic performance during the transesterification of waste frying oil with methanol. Reactions performed using a methanol/oil molar ratio of 9:1 at 90 °C for 5 h gave a fatty acid methyl ester yield of 85.56%. © 2022 Society of Chemical Industry (SCI).

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Opto-electrical properties of 3-hydroxy-4-methoxy benzaldehyde single crystal

Perumal¹,

Ananthi²

2021

Journal of Crystal Growth

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Structural transformations of 3-fluoro and 3-fluoro-4-methoxy benzaldehydes under cryogenic conditions: A computational and low temperature infrared spectroscopy investigation

Cited by 4 publications

References 27 publications

Structure, Vibrational Spectra, and Cryogenic MatrixPhotochemistry of 6-Bromopyridine-2-carbaldehyde: From the Single Molecule of the Compound to the Neat Crystalline Material

Structure, Vibrational Spectra, and Cryogenic MatrixPhotochemistry of 6-Bromopyridine-2-carbaldehyde: From the Single Molecule of the Compound to the Neat Crystalline Material

Oxidation reaction mechanism of hydrothermal carbon microspheres with applications to transesterification after sulfonation

Opto-electrical properties of 3-hydroxy-4-methoxy benzaldehyde single crystal

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