Pyrylocyanines. 35. Squarylium dyes based on tert-butyl-substituted pyrylium and thiopyrylium salts

Abstract

Squarylium dyes based on isomeric di(tert-butyl)methyl-substituted pyrylium, thiopyrylium, and benzopyrylium salts have been synthesized. The dye containing 4, 6-di(tert-butyl)pyrylium residues was converted to its analog with methylpyridinium residues. The PMR and electronic absorption spectra of the dyes obtained were investigated. It was established that deepening of the color from dicarbocyanines to squaraines is characteristic only of dyes containing heterocyclic residues with high or medium electron-donor capacity. For dyes containing heterocyclic residues with low electron-donor capacity the opposite pattern is observed.