The title compounds, 3,4-dimethyl-N-[1-(1H-pyrrol-2-yl)ethylidene]aniline, C14H16N2, (I), and its analogue 3,4-dimethyl-N-[1-(1-thiophen-2-yl)ethylidene]aniline, C14H15NS, (II), both have basic heterocyclic imino structures showing a planar backbone with similar features, but differing in the heteroatoms of the five-membered heterocyclic rings, i.e. N in (I) and S in (II). The dihedral angles formed by the five-membered and benzene rings are 81.78 (8) and 75.89 (7)° for (I) and (II), respectively. In (I), centrosymmetric iminopyrrole dimers are assembled by means of two inverted N-H···N hydrogen bonds and two inverted C-H···π interactions. In (II), however, molecules are linked by nonclassical C-H···N hydrogen bonds in which the molecules act as both hydrogen-bond donors and acceptors, resulting in one-dimensional supramolecular chains.
Keywords: crystal structure; heterocyclic imino structures; hydrogen bonding; one-dimensional supramolecular chains.