Cyanine dyes from seven-membered heterocyclic systems

The condensation of o-aminothiophenol with tetrahydroacetophenone, 2-ethylidenecyclohexanone, and 2-benzylidenecyclohexanone and also the condensation of N-methyl-o-aminothiophenol with 2-benzylidenecyclohexanone has given the bases of derivatives of benzo[b]cyclohexano[f]- and -[e]-1,4-thiazepines. From the hydrochlorides, perchlorates, and quaternary salts of these bases, cyanine dyes have been synthesized. The dyes—norcyanines—exhibit solvatochromism, which is explained by the existence of a hydrogen bond between the molecules of the dye and an alcohol.For part IV, see [3].