The spectroscopic (FTIR, FT-Raman, NMR and UV), first-order hyperpolarizability and HOMO–LUMO analysis of methylboronic acid

The solid phase FTIR and FT-Raman spectra of methylboronic acid (MBA) have been recorded in the regions 400–4000 and 50–4000 cm−1, respectively. The spectra were interpreted interms of fundamentals modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by density functional theory (B3LYP) and HF method with 6-311++G(d,p) as basis set. The vibrational frequencies were calculated for most stable conformer and were compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. 1H and 13C NMR spectra were recorded and 1H and 13C nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV–visible spectrum of the compound was recorded in the region 200–400 nm and the electronic properties HOMO and LUMO energies were calculated by time-dependent TD-DFT approach. Mulliken charges of the MBA molecule was also calculated and interpreted. The geometric parameters, energies, harmonic vibrational frequencies, IR intensities, Raman intensities and absorption wavelengths were compared with the available experimental data of the molecule.

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► The FTIR and FT-Raman spectra of methylboronic acid were recorded.
► The vibrational frequencies were calculated for CT form by DFT and HF method.
► NMR and UV–vis spectra were also recorded and compared with calculated ones.
► Thermodynamic properties of MBA were calculated and discussed.