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The present research has studied the spectral data, thermochemical transformations and hydrolysis of hexafluorosilicates with guanidine containing cations (C22H32Cl2N10)SіF6 (І) and (C21H45N9)(SiF6)1.5 (ІІ) for their potential use as caries-preventive and antibacterial agents. Hexafluorosilicates of the com position I and II were separated as crystalline products of interaction of hexafluorosilicic acid with the methanol solutions of chlorhexidine hydrochloride and polyhexamethylene guanidine hydrochloride. The compounds isolated have been characterized by IR, NMR 19 F, mass-spectrometry, thermogravimetric analysis, potentiometry. According to IR spectroscopy data, “onium” hexafluorosilicates I and II have ionic structures. The vibrations of the groups ν(NH), ν(N + H2) in salts I and II appear as strong absorption bands at 3360-3180 cm –1 ; δ(N + H2) vibrations appear at 1634 and 1637 cm –1 . The strong ν(SiF) and δ(SiF2) stretches of SiF6 2– anions are observed in their characteristic regions (at 744, 734 and 482 cm –1 , respectively). The singlet character of ν(SiF) and δ(SiF2) vibrations indicates the absence of noticeable distortion of symmetry of SiF6 2– anion with regard to Oh. The NMR 19 F spectra of compounds I and II (in DMSO-d6 solutions) have one resonance at –136,70, –135,09 ppm (SiF6 2– ); additional resonance at –123,14 ppm, in the case of II it can be related to the octahedral complex anion [SіF5(ДМСО)] – . The results of thermogravimetric analysis are consistent with a multi-stage thermolysis scheme for hexafluorosilicates I and II. The temperatures of thermolysis beginning of complexes I and II are 270 and 100°C, respectively. The compounds I and II studied are characterized by the predicted tendency to hydrolysis in dilute aqueous solutions with formation of orthosilicic acid and fluoride ions, and it allows considering these salts as potential anticaries agents. The study of the biological activity of these compounds is the subject of further investigations. In recent years, several research groups consisting of experts from Japan, the United States [10-13] and Armenia [1, 8] demonstrated the possible use of ammonium and amino acids hexafluorosilicates as caries-preventive and hyposensitive agents in dental practice. These results [1, 8, 10-13] allow to consider the “onium” hexafluoro silicates as a promising new class of drugs possessing a number of advantages compared to the conventional agents of fluoride caries therapy such as sodium and po tassium fluorides, silver diamine fluoride, tin fluoride and sodium monofluorophosphate. The active components of treatment and prevention of dental caries are also antibacterial agents, including high efficient guanidine de rivatives (chlorhexidine, polyhexamethylene guanidine hydrochloride, etc.) [9, 13]. In principle, introducing guanidine containing cations possessing the antibacterial action into the composition of hexafluorosilicate allows to obtain compounds for which the caries-preventive effect of the anion is intensified by the bactericidal action of the cation. The aim of this work is the synthesis, the study of the structure and properties of chlorhexidine (CH) and polyhexamethylene guanidine (PHMG) hexafluorosilicates – the first representatives of fluoride-containing salts com bined with cations exhibiting the antibacterial activity. Materials and Methods The synthesis of hexafluorosilicates was performed by the ion exchange reaction between methanol solu

Hexafluorosilicates with antibacterial active guanidine containing cations