Abstract
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 center dot center dot center dot X-C intermolecular contacts in which the N center dot center dot center dot X contact distances are longer than those in the corresponding benzylideneanilines.