Solvent and anion facilitated conformational changes in benzylamine substituted thiazolamine

Conformational adjustments in the solid state structures of the syn–anti–syn form of N,N′-(1,4-phenylene bis(methylene))-bis(5-methylthiazol-2-amine) (L) are studied. Changes are attributed to the rotation of the C–N bonds facilitated by different solvents and anions. Two conformational polymorphs of L, one having molecules with S-like geometry and the other with l-like geometry, were crystallized from solutions of L in different solvents. The crystalline salts of the compound L have anti orientation of the thiazole units across the phenylene ring but the extent of conformational adjustments depends on the anions. Conformational adjustments of the organic [H2L]2+ cation in each salt, [H2L]Br2·2H2O (1), [H2L](NO3)2 (2), and [H2L](H2PO4)2·2H3PO4 (3), provide different orientations to methylaminothiazole units. The organocation of the bromide and biphosphate salts has protonated L in S-like geometries, whereas the nitrate salt has cations in l-like geometry. Exceptionally, nitrate ions cause ∼175° twist with respect to the parent compound L across the C–N bond of the C(thiazole)–NH unit to adopt the anti–anti–anti form. Robust hydrogen bonded cyclic motifs are found in the self-assemblies of the salts.