Theoretical study on electronic structures and spectroscopy of triarylborane substituted by thiophene

The electronic structures of a series of triarylborane derivatives were studied using the AM1 method and density function theory (DFT) at B3LYP/6-31G(d) level. Based on the B3LYP/6-31G(d) optimized geometries, the electronic spectra, IR and 13C NMR spectra of these compounds were calculated with the INDO/CIS, AM1 and B3LYP/6-31G(d) methods, respectively. The presence of electron-donating alkyl groups and the increase in the number of thiophene rings in the derivatives lead to the decrease in LUMO-HOMO energy gaps. At the same time, the first absorptions in the electronic spectra and the stretching vibrations of the C-C as well as C-H bonds in the IR spectra of these compounds compared with those of the parent compound are red-shifted. Also, the 13C chemical shifts of the carbon atoms on the phenyl rings in these compounds are upfield relative to those of the same carbon atoms in the parent compound.