Synthesis and electronic absorption spectra of dicyano-derivatives of 4-diethylaminoazobenzene

Abstract

The six dicyano-derivatives of 4-diethylaminoazobenzene in which the cyano-groups and the amino-group occupy different rings have been prepared, mostly by diazotisation of the appropriate dicyanoaniline, followed by coupling to NN-diethylaniline. The 2′,4′- and 2′,6′-dicyano-compounds were prepared more conveniently by a cyanide displacement reaction with a suitable halogen-containing azo-dye precursor. The absorption spectra of the dyes were compared with those of the three monocyano-derivatives and the 2′,4′,6′-tricyano-compound. The intensities of the visible absorption bands confirm that steric interactions are small in the series studied, and thus spectral shifts can be attributed largely to the electronic effect of the cyano-groups. The effects of positional isomerism in the dicyano-compounds can then be assessed reliably. The 2′,4′-derivative was the most bathochromic member of the dicyano-series.