Protonation sites and hydrogen bonding in mono-hydrobromide salts of two N,4-diheteroaryl 2-aminothiazoles

The synthesis and structural characterization of N-(6-methoxypyridin-3-yl)-4-(pyridin-2-yl)thiazol-2-amine mono-hydrobromide monohydrate (3) and N-(6-methoxypyridin-3-yl)-4-(pyrazin-2-yl)thiazol-2-amine mono-hydrobromide 0.35 methanol solvate (4) are reported. The crystal structures of 3 (monoclinic, space group P2(1)/n, Z = 4) and 4 (monoclinic, space group, C2/c, Z = 8) feature N,4-diheteroaryl 2-aminothiazoles showing similar molecular conformations but different sites of protonation and thus distinctly different intermolecular hydrogen bonding patterns. In 3, N-amine-HMIDLINE HORIZONTAL ELLIPSISBr-, N-pyridine(+)-HMIDLINE HORIZONTAL ELLIPSISOwater, and O-water-HMIDLINE HORIZONTAL ELLIPSISBr- hydrogen bonds link protonated N-(6-methoxypyridin-3-yl)-4-(pyridin-2-yl)thiazol-2-amine and water molecules and bromide anions into a three-dimensional hydrogen-bonded network, whereas intermolecular N-methoxypyridine(+)-HMIDLINE HORIZONTAL ELLIPSISNpyrazine hydrogen bonds result in hydrogen-bonded zigzag chains of protonated N-(6-methoxypyridin-3-yl)-4-(pyrazin-2-yl)thiazol-2-amine molecules in 4.

Automated summary

The crystal structures of two compounds show similar molecular conformations but different hydrogen bonding patterns, with one forming a three-dimensional hydrogen-bonded network and the other forming zigzag chains of hydrogen bonds.