Hexafluorosilicates of bis(carboxypyridinium) and bis(2-carboxyquinolinium)

The preparation and characterization of three isomeric carboxypyridinium and carboxyquinolinium hexafluorosilicate salts is described. The salts of the general formulas (LH)2[SiF6] (I–III, L = 2-carboxypyridine, 3-carboxypyridine, 4-carboxypyridine) and (LH)2[SiF6]·2H2O (IV, L = 2-carboxyquinoline) were prepared from the protonation reaction of the corresponding pyridine carbonic acid by the fluorosilicic acid. The compounds were characterized by IR, mass-spectrometry, thermogravimetric analysis, solubility data, and in the case of III by X-ray crystallography. The relationship between the salts solubility and the H-bonding system was analysed.