Pnicogen, halogen and hydrogen bonds in (E)-1-(2,2-dichloro-1-(2-nitrophenyl)vinyl)-2-(para-substituted phenyl)-diazenes

Schiff base condensation of 2-nitrobenzaldehyde with (para-substituted phenyl)hydrazine in the presence of CH3COONa in EtOH at 80 °C produces (E)-1-(para-substituted phenyl)-2-(2-nitrobenzylidene)hydrazines [−OCH3 (1), −CH3 (2), −H (3), −Br (4), −Cl (5), −F (6)]. CuCl catalyzed olefination of 1−6 with CCl4 in the presence of tetramethylethylenediamine (TMEDA) in DMSO leads to (E)-1-(2,2-dichloro-1-(2-nitrophenyl)vinyl)-2-(para-substituted phenyl)-diazenes [−OCH3 (7), −CH3 (8), −H (9), −Br (10), −Cl (11), −F (12)], respectively. 1–12 were characterized by 1H and 13C NMR spectroscopies, ESI-MS, elemental and X-ray diffraction (for 8, 9 and 12) analysis. The single crystal X-ray analysis of 8, 9 and 12 evidence the intramolecular N⋯Cl pnicogen bonds which is significantly strengthened in view of the planarity of the four atoms involved in the 1,4-membered synthon. The intermolecular halogen and hydrogen bonds also contribute to stabilize the crystal structures of 8, 9 and 12. In DMSO solution 1–12 exist in the E-isomeric form, which stabilized by inter- and intramolecular noncovalent interactions. Solvatochromic behavior on UV–vis absorption spectra of azo dyes 7–12 were studied in CH2Cl2, DMF and MeOH, which λmax is dependent on the attached substituents at para- position of aromatic moiety.