Crystallographic and spectroscopic studies of 5-arylidene-2-amino-imidazol-4-ones

The series of 5-arylidene-2-anilino/benzylamino/isoniazid-imidazol-4-ones was studied. The X-ray structure analysis, performed for four representatives, confirmed Z configuration of an exocyclic double bond for all structures and showed that the hydrogen bond pattern in studied structures strongly depends on tautomeric form of 2-amino-imodazolone moiety as well as on properties of solvent molecules in the crystals. Stacking details and various motifs of multiple hydrogen bonded network, formed in the crystals by all possible tautomers, were discussed. Crystallographic investigations of selected objects have been supported by 1H and 13C NMR data, obtained for the extended set of 5-arylidene-2-amino-imidazol-4-ones. Comparison of all data allowed to analyze the tautomeric equilibrium of the investigated compounds, both in solution and in a solid state.