DFT, FT-Raman, FT-IR, solution and solid state NMR studies of 2,4-dimethoxyphenylboronic acid

The possible stable forms and molecular structures of 2,4-dimethoxyphenylboronic acid (2,4-dmpba) have been experimentally and theoretically studied using FT-IR, Raman and solution and solid state NMR spectroscopic methods. FT-IR and Raman spectra were recorded in the region of 4000–400 cm−1. 13C cross-polarization magic-angle spinning NMR and solution phase 1H, 13C and HETCOR NMR spectra of 2,4-dmpba ((CH3O)2C6H3B(OH)2) have been 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. The vibrational wavenumbers and 1H, 13C NMR chemical shifts of 2,4-dmpba have been calculated by means of B3LYP density functional methods with 6-31++G(d,p) basis set. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. Comparison between the experimental and the theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and nuclear magnetic shielding tensors. Furthermore, the cis–trans (ct) form of 2,4-dmpba with Cs point group has been found to be the most stable conformer.