Electronic absorption spectra of some julolidine (2,3,6,7-tetrahydro-1H, 5H-benzo[ij]quinolizine) analogues of 4-dimethylaminoazobenzenes

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Abstract
Absorption spectra of 9-phenylazojulolidine and nine para-substituted derivatives have been determined for solutions in ethanol. Pronounced bathochromic shifts of the first-frequency band are observed relative to the corresponding derivatives of 4-dimethylaminoazobenzene. A linear relation is found between the difference in the absorption maxima of the dyes and their azonium salts and the appropriate Hammett substituent constant. 9-Pentafluorophenylazojulolidine does not form an azonium cation in ethanolic hydrogen chloride.