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.