Extended conjugation in di- and tri-arylmethane dyes. Part 5. Vinylogues and ethynologues of Victoria Blue

Novel vinylogues and ethynologues of the naphthyldiphenylmethane dye system have been synthesised and their spectral parameters measured. The extended conjugation brings about red shifts of the absorption bands relative to the parent dyes. Although this effect is generally greater for the alkynyl derivatives, the vinylogue is better able to accommodate the peri-hindrance associated with the 4-dimethylamino-1-naphthyl group.