Spectrochim Acta A Mol Biomol Spectrosc
February 2025
The most stable conformer of laser-ablated diflunisal has been isolated in a supersonic expansion and experimentally detected through high-resolution chirped-pulse rotational spectroscopy. State-of-the-art chemical calculations allowed to understand the nature of the strong stabilization of the detected conformer and its atropisomer among a total of sixteen theoretically predicted conformers and confirmed the presence of a resonance assisted hydrogen bond (RAHB) between the hydroxyl hydrogen atom and the carbonyl oxygen atom of the carboxylic acid group. The comparison of the experimental data from this work and the information found in the literature about the molecule in condensed phases corroborates the existence of these two atropisomers and is contextualized within the complexation arrangement of diflunisal with relevant proteins.
View Article and Find Full Text PDFThe combination of atropisomerism and chirality in flurbiprofen is shown to be relevant concerning its pharmacological activity. The two most stable conformers of a total of eight theoretically predicted for each R- or S- flurbiprofen enantiomers have been isolated in the cooling conditions of a supersonic jet and structurally characterized by laser ablation Fourier transform microwave spectroscopy. The detected conformers, whose structure is mainly defined by three dihedral angles, only differ in the sign of the phenyl torsion angle giving rise to S and R atropisomers.
View Article and Find Full Text PDFThe rotational spectrum of laser-ablated gallic acid has been recorded using CP-FTMW spectroscopy. Two rotamers have been detected, and their rotational spectra have been assigned and analyzed to obtain the molecular spectroscopic parameters. The observed rotamers have been unambiguously identified in the light of theoretical computations, based on the comparison of the experimental line intensities and rotational parameters with the rotational constants and electric dipole moments predicted from theoretical calculations.
View Article and Find Full Text PDFThe broadband rotational spectrum of jet-cooled laser-ablated thioproline was recorded. Two conformers of this system were observed and identified with the help of DFT and ab initio computations by comparison of the observed and calculated rotational constants and N quadrupole coupling constants as well as the predicted energies compared to the observed relative populations. These conformers showed a mixed bent/twisted arrangement of the five-membered ring similar to that of the related compound thiazolidine with the N-H bond in axial configuration.
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