Conformational Stability of Ibuprofen: Assessed by DFT Calculations and Optical Vibrational Spectroscopy

Abstract

A thorough conformational analysis of ibuprofen [2-(4-isobutylphenyl) propionic acid] was carried by out, using density functional theory (DFT) calculations coupled to optical vibrational spectroscopy (both Raman and FTIR). Eight different geometries were found to be energy minima. The relative orientations of the substituent groups in the ibuprofen molecule, which can be considered as a para-substituted phenyl ring, were verified to hardly affect its conformational stability. The internal rotations converting the calculated conformers of ibuprofen were studied and the intramolecular interactions governing the conformational preferences of the molecule were analyzed by quantitative potential energy deconvolution using Fourier type profiles. The harmonic vibrational frequencies and corresponding intensities were calculated for all the conformers obtained, leading to the assignment of the spectra, and evidencing the sole presence of one of the lowest energy conformers in the solid state. Vibrational spectroscopic proof of intermolecular hydrogen bonds between the carboxylic groups of adjacent ibuprofen molecules, leading to the formation of dimers, was also obtained. ß

Natural halloysite nanotubes as mesoporous carriers for the loading of ibuprofen

“…6e-h), the peaks at 2956 and 2871 cm À1 are attributed to the asymmetric and symmetric stretching -CH 3 vibration of IBU. The peaks at 2924 and 2851 cm À1 are attributed to the asymmetric and symmetric stretching -CH 2 vibration of IBU [68]. Both sets of vibrational bands confirmed the uptake of IBU in the halloysite.…”

“…Vueba et al [68] used density functional theory methods to calculate the free C@O vibration at 1765 cm À1 . In fact, the stretching C@O vibration showed a downward shift to lower wavenumbers (1700-1725 cm À1 ) due to the formation of hydrogen bonds between the carboxyl groups of IBU and the generated hydrogenbonded aggregates, such as dimers and trimers with linear or cyclic forms, in condensed phases [68,69].The carbonyl band at 1721 cm À1 indicates that IBU existed as hydrogen-bonded aggregates in all of the IBU-loaded samples.…”

Dielectric Spectroscopy in Ibuprofen-Dioxane Mixture

“…Unfortunately, the experimental value of µ 0 is not available for neat IBP. Although, it is reported in the literature [33] that the dipole moment of IBP is mostly originated from O=C-O-H group. According to Bras et al [1] the Molecular Dynamics (MD) simulation reveals a strong tendency of IBP to form noncovalent molecular aggregates such as dimer (µ 0 = 1.29D to 2.15D) and trimer (µ 0 = 1.68D to 2.50D) either cyclic or linear, where cyclic structures were found to have a smaller dipole moment and less g k " value (∼0.3 (for cyclic) and ∼0.8 (for linear)) at T = 360K.…”

New sustained release of Zidovudine Matrix tablets − cytotoxicity toward Caco-2 cells

“…Thus, when studying new pharmaceutical formulations, it is important to determine the presence of possible incompatibilities between their components. Raman spectroscopy, which has been widely applied to this type of preformulation studies [60][61][62][63] , was presently used with a view to detect solid-state interactions between AZT and the considered excipients and, consequently, to assess the drug-excipients compatibility in all examined formulations. A 1:1 (w:w) drug:excipient ratio was chosen, since this is known to maximize the likelihood of observing intermolecular interactions.…”