The nature of chromaticity of triphenylmethane, xanthene, phthalocyanine, and thiazine dyes

Works concerned with the origin of coloration of organic compounds are reviewed. Proofs are given that individual triphenylmethane, xanthene, phthalocyanine, and thiazine dye molecules do not absorb light in the visible range and are not chromogens, that is, do not determine compound chromaticity. Individual molecules of these dyes should be considered chromophoric particles, necessary but insufficient for coloration generation. Elementary chromogens of the dyes under consideration are dimers (supramolecular particles). The blue coloration of aromatic compound azulene has a similar origin.