Synthesis, structure and some properties of 2-, 3-, 4-aminophenylacetic acids hexafluorosilicates

Abstract

A method for the synthesis of new potential anti-caries agents, 2-, 3-, 4-aminophenylacetic acids hexafluorosilicates, whose ammonium cations contain a pharmacophore of anti-inflammatory activity, has been proposed. The composition and ionic structure of the synthesized compounds [2-, 3-, 4-HO(O)CCH2C6H4NH3]2SiF6 (I–III, respectively) were determined by the methods of elemental analysis, IR, 1H, 19F NMR, mass-spectrometry. In the IR spectra of I–III salts, the bands of valence and deformation vibrations of ammonium cations (NH3+), (NH3+) appear at 3179–2906 cm–1 and 1630–1619 cm–1; bands (SiF), (SiF2) of SiF62– anions are fixed at 774–703 cm–1, and 476–436 cm–1, respectively; and the doublet nature of (SiF2) vibrations in the I and II spectra may indicate a decrease in the anion geometry compared to the octahedral Oh. In the 19F NMR spectra of I–III aqueous solutions, intense singlet signals with characteristic values (19F) about –130 ppm and constants J(Si29–19F)=106.7 Hz, 107.3 Hz, and 107.9 Hz, respectively, correspond to SiF62– anions. The solubility of I–III in water, methanol, ethanol (96%) and dimethylsulfoxide was determined, the influence of the nature of the solvent and cation on the solubility characteristics of salts was characterized. For diluted (110–3, 110–4 mol/l) aqueous solutions of I–III, a decrease in the pH values to 3.38–3.70 was observed resulted from the hydrolysis process, a possible intermediate of which according to NMR 19F is an aqua-anion [SiF5(H2O)]–.