Crystal structures of (E)-N′-(2-hy­dr­oxy-5-methyl­benzyl­­idene)isonicotinohydrazide and (E)-N′-(5-fluoro-2-hy­dr­oxy­benzyl­­idene)isonicotinohydrazide

Two derivatives of the well-known iron chelator, (E)-N′-(2-hy­droxy­benzyl­idene)isonicotinohydrazide (SIH), substituted in the 5-position of the 2-hy­droxy­benzene ring by a methyl and a fluorine group viz. (E)-N′-(2-hy­droxy-5-methyl­benzyl­idene)isonicotinohydrazide, C14H13N3O2, (I), and (E)-N′-(5-fluoro-2-hy­droxy­benzyl­idene)isonicotinohydrazide, C13H10FN3O2, (II), have been prepared and characterized by single-crystal X-ray diffraction, 1H NMR and mass spectrometry. The mol­ecules of both compounds deviate slightly from planarity [r.m.s. deviations are 0.145 and 0.110 Å for (I) and (II), respectively] and adopt an E conformation with respect to the double bond of the hydrazone bridge. In each mol­ecule, there is an intra­molecular O—H⋯N hydrogen bond forming an S(6) ring motif. The dihedral angles between the mean planes of the isonicotinoyl ring and the cresol ring in (I) or the fluoro­phenol ring in (II) are 10.49 (6) and 9.43 (6)°, respectively. In the crystals of both compounds, zigzag chains are formed via N—H⋯N hydrogen bonds, in the [10-1] direction for (I) and [010] for (II). In (I), the chains are linked by weak C—H⋯π and π–π stacking inter­actions [centroid-to-centroid distances = 3.6783 (8) Å; inter-planar angle = 10.94 (5)°], leading to the formation of a three-dimensional supra­molecular architecture. In (II), adjacent chains are connected through C—H⋯O hydrogen bonds to form sheets parallel to (100), which enclose R44(30) ring motifs. The sheets are linked by weak C—H⋯π and π–π [centroid-to-centroid distance = 3.7147 (8) Å; inter-planar angle = 10.94 (5)°] inter­actions, forming a three-dimensional supra­molecular architecture.