Halogen-bonding in 3-nitrobenzaldehyde-derived dichlorodiazadienes

A set of 4,4-dichloro-1,2-diazabutadienes derived from 3-nitrobenzaldehyde was prepared by the copper catalyzed reaction of the corresponding hydrazones with CCl4 in the presence of TMEDA. The structure of all products was confirmed by H-1 and C-13 NMR spectra and ESI-MS. X-ray diffraction revealed Cl center dot center dot center dot O halogen binding in the crystal form for some dienes. Moreover, Br center dot center dot center dot pi and Cl center dot center dot pi types of halogen bonds are observed. Azo dyes absorb in the UV-Vis region with the lambda(max) located at about 234-437 nm in CH2Cl2, DMF and MeOH. Both absorption intensity and lambda(max) is dependent on the solvent polarity and the electron-withdrawing/donating ability of para-substituents on the aromatic moiety of the dichlorodiazadienes. [GRAPHICS]