FT‐Raman, FT‐IR spectra and DFT calculations on monomeric and dimeric structures of 5‐fluoro‐ and 5‐chloro‐salicylic acid

Abstract

The experimental and theoretical study on the structures and vibrations of 5-fluoro-salicylic acid and 5-chloro-salicylic acid (5-FSA and 5-ClSA, C 7 H 5 FO 3 and C 7 H 5 ClO 3 ) is presented. The Fourier transform infrared spectra (4000-400 cm −1 ) and the Fourier transform Raman spectra (4000-50 cm −1 ) of the title molecules in the solid phase were recorded. The molecular structures, vibrational wavenumbers, infrared intensities, Raman intensities and Raman scattering activities were calculated for a pair of molecules linked by the intermolecular O-H· · ·O hydrogen bond. The geometrical parameters and energies of 5-FSA and 5ClSA were obtained for all eight conformers/isomers from density functional theory (DFT) (B3LYP) with 6-311++G(d,p) basis set calculations. The computational results identified the most stable conformer of 5-FSA and 5-ClSA as the C1 form. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The spectroscopic and theoretical results were compared with the corresponding properties for 5-FSA and 5-ClSA monomers and dimer of C1 conformer. The optimized bond lengths, bond angles and calculated wavenumbers showed the best agreement with the experimental results.

Spectroscopic (FT-IR/FT-Raman) and computational (HF/DFT) investigation and HOMO/LUMO/MEP analysis on 1,1-difluoro-2-vinyl-cyclopropane

“…Mehmet Karabacak et al assigned the strong bands at 1254 and 1222 cm À1 in the FT-IR spectrum due to the C-F stretching mode and their counterpart in the Raman spectrum at 1274 and 1245 cm À1 . The theoretically computed scaled value of 1271 and 1240 cm À1 at B3LYP/6-311+G (d,p) showed good agreement with experimental results for 5-flouro salicylic acid [24]. In the present work wave numbers at 1290 cm À1 and 1210 cm À1 in FT-IR and FT-Raman are assigned to C-F stretching vibration for 1DF2VCP.…”

DFT calculations and experimental FT-IR, FT-Raman, NMR, UV–Vis spectral studies of 3-fluorophenylboronic acid

“…The O-H stretching modes for 2,3-difluorophenylboronic acid were also calculated at 3609 and 3339 cm À1 as expected pure stretching modes accordance TED contributing 100%. This frequency is observed at 3244 cm À1 in FT-IR for structurally similar molecule [41]. The O-H peaks were observed at 3392 and 3257 cm À1 in FT-IR spectrum for acenaphthene-5-boronic acid [28].…”

“…In international tables for crystallography, the C-F bond length is 1.377 Å for 3-fluorophenylboronic acid [6]. The C-F bond length was observed and calculated at 1.357 Å for 5-fluoro salicylic acid (similar structure for our molecule) [40,41]. In this work, the bond C-F is calculated at 1.357 Å, by using B3LYP/6-311G++(d,p) basis set, showing good coherent related paper.…”

Functional β-cyclodextrin coating by electrodeposition on stainless steel for drug loading and release

“…The β-CD-S was cleaned with ethyl acetate until no methyl salicylate was detected by UV-visible spectrometry at 306 nm. The degree of substitution was about 1.3 calculated on the basis of 1 H NMR(AVANCE 500 MHz) spectrum( Fig.1) [21,22] . …”