Crystal structures and Hirshfeld surface analyses of ()-1-[1-(4--butyl-phen-yl)-2,2-di-chloro-ethen-yl]-2-phenyl-diazene, ()-1-[1-(4--butyl-phen-yl)-2,2-di-chloro-ethen-yl]-2-(4-methyl-phen-yl)diazene, ()-1-[1-(4--butyl-phen-yl)-2,2-di-chloro-ethen-yl]-2-(4-meth-oxy-phen-yl)diazene and ()-1-[1-(4--butyl-phen-yl)-2,2-di-chloro-ethen-yl]-2-(3-methyl-phen-yl)diazene.

The crystal structures and Hirshfeld surface analyses of four similar azo compounds are reported. ()-1-[1-(4--Butyl-phen-yl)-2,2-di-chloro-ethen-yl]-2-phenyl-diazene, CHClN, (), and ()-1-[1-(4--butyl-phen-yl)-2,2-di-chloro-ethen-yl]-2-(4-methyl-phen-yl)diazene, CHClN, (), crystallize in the monoclinic space group 2/ with = 8, and ()-1-[1-(4--butyl-phen-yl)-2,2-di-chloro-ethen-yl]-2-(4-meth-oxy-phen-yl)diazene, CHClNO, (), in the monoclinic space group 2/ with = 4. ()-1-[1-(4--Butyl-phen-yl)-2,2-di-chloro-ethen-yl]-2-(3-methyl-phen-yl)diazene, CHClN, (), crystallizes in the triclinic space group with = 4 and comprises two mol-ecules ( and ) in the asymmetric unit. In the crystal structures of () and (), mol-ecules are linked by C-H⋯π and C-Cl⋯π inter-actions, forming layers parallel to (02), while mol-ecules of () are linked by C-H⋯O contacts, C-H⋯π and C-Cl⋯π inter-actions forming layers parallel to (02). The stability of the mol-ecular packing is ensured by van der Waals forces between these layers. In the crystal structure of (), mol-ecules are linked by C-H⋯π and C-Cl⋯π inter-actions, forming a tri-periodic network.