Two polymorphs of N,N′-diphenyl-2-[1-(propyl­amino)­ethyl­idene]propanedi­amide

Two polymorphs of the title compound, C(20)H(23)N(3)O(2), have been isolated. Polymorph (I) crystallizes in the monoclinic space group P2 (1)/n and polymorph (II) in the tetra­gonal space group I4 (1)/a. The main difference between the two polymorphs on the mol­ecular level is the orientation of the n-propyl group. This group is anti­periplanar in (I) and synclinal in (II). The core of the mol­ecule consists of two carbamoyl units bound to an enamine unit. The most prominent features are intra­molecular N—H⋯O hydrogen bonds in both polymorphs. Both polymorphs form dimers with graph set R (2) (2)(12) via inter­molecular N—H⋯O hydrogen bonds. Adjacent dimers of (I) are connected via a weak C—H⋯O inter­action, resulting in a chain parallel to the crystallographic a-axis. The dimers of (II) are connected by weak C—H⋯π inter­actions, forming inter­molecular chains along the c-axis direction.