Theoretical study on triphenylamine-based sensors of dicarboxylic acids

Density functional theory and time-dependent density functional theory calculations have been carried out on complexes formed by a triphenylamine-based chemosensor and aliphatic dicarboxylic acids of different chain-length. Optimum geometries, binding energies as well as oscillator strengths for the absorption spectra of the complexes are calculated in an effort to determine the factors affecting the selectivity of the particular sensor for the acids considered. The results show that, in agreement with experimental studies of selective recognition in solution, the binding of the dicarboxylic acids to the chemosensor is through hydrogen bonding at two sites except for the longest-chain acid, suberic acid. The greatest effect on the first absorption peak is found for the complex with 2,2-dimethyl malonic acid and the greatest NMR shift (for the amidic proton) is calculated for the complex with adipic acid, which shows that in the gas phase, there is no selective recognition of the above chemosensor for glutaric acid, which is reported to be the case in the experimental findings in solution.