Effects of normal and reverse micellar environment on the spectral properties, isomerization and aggregation of a hydrophilic cyanine dye

The spectral properties, cis→trans isomerization and aggregation of the anionic hydrophilic cyanine 1, were studied in isooctane/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water, cyclohexane–hexanol/Triton X-100/water reverse micelles and in aqueous solutions in the presence of surfactants. The incorporation of 1 into micelles leads to dimer→monomer decomposition and cis→trans isomerization. In AOT reverse micelles with w0⩾5 (w0=[H2O]/[AOT]) 1 forms J aggregates at concentrations much lower than one dye molecule per one micelle; at w0=50 the most probable aggregation number is 3. Premicellar J aggregates of 1 are observed with both cationic and anionic surfactants, but not with Triton X-100.