Infrared, Raman and temperature-dependent NMR spectra, vibrational assignments, normal coordinate analysis, and DFT calculations of benzoxazoline-2-thione

X-ray, tautomeric preference, vibrational spectra, and density functional studies on benzoxazole and benzoxazoline derivatives

“…5-8). Therefore, rough visual inspections on the vibrational spectra suggest the presence of only thionic forms at room temperature, similar to the result of previous NMR analyses [23]. This is because thiolic species contain a smaller number of strong bands.…”

“…BO-NSH and BO-NSMe are too minor if they exist (see vibrational analyses). NMR measurements recorded varying the temperature from -90 C to +90 C suggest the presence of only thionic forms in DMSO-d 6 [23].…”

“…Vibrational spectra of BO-NSH and BO-NHS were already analyzed with DFT but with small basis sets [23,24], or with mode Fig. 9.…”

“…1) to assess the substitutional effects on the structure and vibrational spectra. We calculated gas-phase geometries and vibrational spectra of bis(BO-NS)Me, BO-NSH, BO-NHS, BO-NSMe, and BO-NMeS with density functional theory (DFT) using B3LYP hybrid functional, which has been already proved to be very effective for vibrational studies of analogous compounds by using at least double-z Pople basis sets [23][24][25][26][27][28][29][30][31]. The computed vibrational frequencies, and IR/Raman intensities were used to simulate the vibrational spectra and to identify normal modes in the experimental vibrational spectra.…”

Tautomeric conversion, vibrational spectra, and density functional studies on peripheral sulfur derivatives of benzothiazole and benzothiazoline isomers

“…However, temperature-dependent NMR measurements between -90°C to +90°C suggest the presence of only benzothiazoline isomer for R = H [1]. An analogous conclusion is drawn from NMR studies when the ring sulfur atom is replaced with an oxygen atom [2]. In this study, tautomerism of the sulfur derivatives of benzothiazoles and benzothiazolines, which have several potent technological applications [3][4][5], will be discussed via potential energy surface (PES) scans that connect the two isomeric forms and vibrational spectral analyses.…”