4‐(4‐Chlorobenzylidenehydrazonomethyl)benzonitrile and the bromo and iodo analogs

4‐Cyano‐4′‐chlorobenzalazine [systematic name: 4‐(4‐chlorobenzylidenehydrazonomethyl)benzonitrile], C₁₅H₁₀ClN₃, occurs in two polymorphs. Polymorph A is isostructural with the corresponding dichloro compound. Polymorph B is isostructural with the bromo and iodo analogs, viz. C₁₅H₁₀BrN₃ and C₁₅H₁₀IN₃, respectively. The latter three structures all have approximately linear C—N...X—C intermolecular contacts in which the N...X contact distances are longer than those in the corresponding benzylideneanilines.