Noncovalent complexes of tetramethylammonium with chlorine anion and 2,5-dihydroxybenzoic acid as models of the interaction of quaternary ammonium biologically active compounds with their molecular targets: A theoretical study

A theoretical study of the interaction of tetramethylammonium cation with chlorine anion and 2,5-dihydroxybenzoic acid modeling a carboxylic group and an aromatic ring of side radicals of proteins has been performed by the DFT/B3LYP/6-31++G^** and MP2/6-31++G^** theoretical methods. To evaluate how the solvation affects the interaction, the Polarizable Continuum Models method has been employed. The calculated interaction energies of the noncovalent complexes were compared with the experimental data describing the stability of some noncovalent complexes of a dication of bisquaternary ammonium salt decamethoximun with Cl^- and 2,5-dihydroxybenzoic acid obtained with the mass-spectrometric technique.