Association and solvolysis processes in solutions of alkyl-substituted dipyrrolylmethenes according to spectral investigations

Results are reported on spectral investigation of alkylated dipyrrolylmethenes hydrohalides in organic solvents of various nature. The pigments were shown to exist in the concentrated solutions in benzene, chloroform, and dimethyl sulfoxide predominantly as associates, and in dilute solutions, as molecular salts. In dimethylformamide alongside an associated and protonated forms a nonprotonated form of dipyrrolylmethenes was present originating from the solvolytic dissociation of salts. The principal structural and solvation factors are considered governing the spectral characteristics and the stability of chemical forms of dipyrrolylmethenes.