CROWN-CONTAINING STYRYL DYES .19. COMPLEXATION AND CATION-INDUCED AGGREGATION OF CHROMOGENIC AZA-15-CROWN-5-ETHERS

Complexation of styryl dyes containing the N-phenylaza-15-crown-5 frag ment (trans-2a,b) with Ca2+ ions in MeCN was studied. Unlike cationic dye trans-2a, betaine trans-2b forms both complexes of 1:1 stoichiomet ry and aggregates consisting of four dye molecules and one Ca2+ ion. C ation-induced aggregation was observed also for the analog of dye tran s-2b, which contains a dimethylamino group instead of an azacrown ethe r fragment (trans-3). Apparently, the interaction between a metal cati on and sulfo groups of molecules trans-2b or trans-3 makes the main co ntribution to the stability of aggregates. The dependence of the stabi lity of aggregates on the nature of the metal cation was studied.