Crystal structures and Hirshfeld surface analyses of (E)-1-[1-(4-ferf-butylphenyl)-2,2-dichloroethenyl]-2-phenyldiazene, (E)-1-[1-(4-ferf-butylphenyl)-2,2-dichloroethenyl]-2-(4-methylphenyl)diazene, (E)-1-[1-(4-ferf-butylphenyl)-2,2-dichloroethenyl]-2-(4-methoxyphenyl)diazene and (E)-1-[1-(4-ferf-butyl-phenyl)-2,2-dichloroethenyl]-2-(3-methylphenyl)diazene.

The crystal structures and Hirshfeld surface analyses of four similar azo compounds are reported. (E)-1-[1-(4-tert-Butylphenyl)-2,2-dichloroethenyl]-2-phenyldiazene, C₁₈H₁₈Cl₂N₂, (I), and (E)-1-[1-(4-tert-butylphenyl)-2,2-dichloro-ethenyl]-2-(4-methylphenyl)diazene, C₁₉H₂₀Cl₂N₂, (II), crystallize in the mono-clinic space group C2/c with Z = 8, and (E)-1-[1-(4-tert-butylphenyl)-2,2-dichloroethenyl]-2-(4-methoxyphenyl)diazene, C₁₉H₂₀Cl₂N₂O, (III), in the monoclinic space group P2₁/c with Z = 4. (E)-1-[1-(4-tert-Butylphenyl)-2,2-dichloroethenyl]-2-(3-methylphenyl)diazene, C₁₉H₂₀Cl₂N₂, (IV), crystallizes in the triclinic space group P1 with Z = 4 and comprises two molecules (A and B) in the asymmetric unit. In the crystal structures of (I) and (II), molecules are linked by C--H⋯π and C--CI⋯π interactions, forming layers parallel to (202), while molecules of (III) are linked by C--H⋯O contacts, C--H⋯π and C--CI⋯π interactions forming layers parallel to (302). The stability of the molecular packing is ensured by van der Waals forces between these layers. In the crystal structure of (IV), molecules are linked by C--H⋯π and C--CI⋯π interactions, forming a tri-periodic network. [ABSTRACT FROM AUTHOR]