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Abstract: Interesting hydrogen-bonded supramolecular patterns have been achieved by hexafluorosilicate anion in the crystal structures of bis(thiabendazole) hexafluorosilicate dihydrate 1 and bis(pyrimethamine) hexafluorosilicate 2. In compound 1, the nitrogen atom of the benzimidazole ring rather than that of the thiazole ring is protonated. Water molecule is hydrogen-bonded with SiF6 2− anion through O–H⋯F hydrogen bonds to form a twelve membered cyclic hydrogen-bonded cluster. This cluster is self-organized to form a supramolecular chain. In the crystal structure of compound 2, the asymmetric unit contains two crystallographically independent protonated pyrimethamine (PMN) cations and a hexafluorosilicate SiF6 2− anion. The combination N–H⋯F and N–H⋯N hydrogen bonds results in the formation of complementary DADA (D and A represent donor and acceptor, respectively) array motif. It confirms that DADA array motif is a robust synthon in the crystal structures of diaminopyrimidine salts. [Copyright &y& Elsevier]