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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]

Polymorphs of 2-amino-4,6-dimethoxypyrimidine [ADMP (1)], 2,4-diamino-6-methyl-1,3,5-triazine [DAMT ( 2 )], 2,4-diamino-6-phenyl-1,3,5-triazine [DAPT ( 3 )] and a solvate of DAPT with DMF solvent, [DAPT·DMF ( 4 )] were obtained either during a systematic screening using various solvents or by serendipity. These polymorphs and solvates were then characterized using single crystal X-ray diffraction technique and their structural and supramolecular aspects are analyzed. The supramolecular architecture of compounds ( 1 – 4 ) are predominantly hydrogen bonded via N–H⋯N base pairs. These base pairs are formed either between crystallographically independent molecules in the lattice or between symmetry related molecules. The molecular self assembly process involved in 2 , 3 and 4 , facilitates the formation of some base pair motifs with graph-set of R 2 2 (8) and a rare non-complementary base pair motif with graph-set R 2 2 (10). The other interesting supramolecular patterns and non-covalent interactions which lead to the formation of new forms are discussed in detail. [ABSTRACT FROM AUTHOR]