“…Symmetric mono‐, tri‐, penta‐, and heptamethine cyanine dyes, both cationic and anionic (having negatively charged sulfonate groups) with various heterocycles (benzimidazolyl, benzothiazolyl, benzoxazolyl) and substituents in heterocycles, were studied. Trimethine cyanines (carbocyanines) also had various substituents in the meso position of the polymethine chain (CH 3 , C 2 H 5 , CH 3 O, CH 3 S, Cl), since meso ‐substituted thiacarbocyanines were previously characterized as effective probes for biomacromolecules [7,8,23,24]. Also studied were squarylium dyes, including squarylium indo‐ and thiacyanines with anionic sulfonate groups.…”