DFT, FT-Raman, FT-IR, liquid and solid state NMR studies of 2,6-dimethoxyphenylboronic acid

Possible stable forms and molecular structures of 2,6-dimethoxyphenylboronic acid (2,6-dmpba) were studied experimentally and theoretically using FT-IR, Raman, liquid–solid state NMR and XRD spectroscopic methods. FT-IR and Raman spectra were recorded in the region of 4000–200 cm−1. 13C cross-polarization magic-angle spinning NMR and liquid phase 1H, 13C and HETCOR NMR spectra of 2,6-dmpba ((CH3O)2C6H3B(OH)2) were reported. The optimized geometric structures concerning to the minimum on the potential energy surface was investigated by Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method together with 6-31++G(d,p) basis set. Vibrational wavenumbers and 1H, 13C NMR chemical shifts of 2,6-dmpba were calculated by means of B3LYP density functional methods with 6-31++G(d,p) basis set. Comparison between the experimental and theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and nuclear magnetic shielding tensors. Furthermore, reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method.