Bases, solvates and salts: new benzimidazole- and pyridine-scaffolded ligands

The inter­molecular inter­actions in the structures of a series of Schiff base ligands have been thoroughly studied. These ligands can be obtained in different forms, namely, as the free base 2-[(2E)-2-(1H-imidazol-4-yl­methyl­idene)-1-methyl­hydrazin­yl]pyridine, C10H11N5, 1, the hydrates 2-[(2E)-2-(1H-imidazol-2-yl­methyl­idene)-1-methyl­hydrazin­yl]-1H-benzimidazole monohydrate, C12H12N6·H2O, 2, and 2-{(2E)-1-methyl-2-[(1-methyl-1H-imidazol-2-yl)methyl­idene]hydrazin­yl}-1H-benz­imidazole 1.25-hydrate, C13H14N6·1.25H2O, 3, the monocationic hydrate 5-{(1E)-[2-(1H-1,3-benzo­diazol-2-yl)-2-methyl­hydrazinyl­idene]meth­yl}-1H-imidazol-3-ium tri­fluoro­methane­sulfonate monohydrate, C12H13N6+·CF3O3S−·H2O, 5, and the dicationic 2-{(2E)-1-methyl-2-[(1H-imidazol-3-ium-2-yl)methyl­idene]hydrazin­yl}pyridinium bis­(tri­fluoro­methane­sulfonate), C10H13N52+·2CF3O3S−, 6. The connection between the forms and the preferred inter­molecular inter­actions is described and further studied by means of the calculation of the inter­action energies between the neutral and charged components of the crystal structures. These studies show that, in general, the most important contribution to the stabilization energy of the crystal is provided by π–π inter­actions, especially between charged ligands, while the details of the crystal architecture are influenced by directional inter­actions, especially relatively strong hydrogen bonds. In one of the structures, a very inter­esting example of the nontypical F⋯O inter­action was found and its length, 2.859 (2) A, is one of the shortest ever reported.