Supramolecular structures of J-aggregates of carbocyanine dyes in solution

Light- and small-angle neutron scattering as well as cryo-transmission elec tron microscopy (cryo-TEM) studies were performed to probe the structure of J-aggregates formed by a series of achiral dye molecules of the 5,5',6,6'- tetrachlorobenzimidacarbocyanine chromophore having 1,1'-dialkyl substituen ts combined with 3,3'-bis(4-sulfobutyl)-3,3'-bis(4-carboxybutyl) or 3,3'-bi s(3-carboxypropyl) substituents. Assemblies that display a dependence on th e substituents different complex supramolecular structures of nanometer-to- micrometer size have been directly visualized by cryo-TEM. The superstructu res span from monomolecular layers formed by the 1,1'-diethyl-3,3'-bis(4-su lfobutyl) derivative and stacks of bilayer ribbons in the case of the 1,1'- dioctyl-3,3'-bis(4-carboxybutyl) derivative to twisted ropelike structures for the chiral aggregate of the 1,1'dioctyl-3,3'-bis(3-carboxypropyl)-subst ituted chromophore.