Structural conditions for spontaneous generation of optical activity in J-aggregates

Achiral molecules of 5,5',6,6'-tetrachlorobenzimidacarbocyanine dyes having 1,1'-di-n-alkyl substituents longer than hexyl combined with 3,3'-bis(2-acidoethyl) or 3,3'-bis(3-acido-n-propyl) substituents form J-aggregates whose absorption spectrum exhibits Davydov-split subbands that display strong circular dichroism, indicating the enantioselective formation of chiral J-aggregates. In this way, for the first time, in the liquid phase self-organization of achiral dye molecules to chiral supramolecular aggregates has been realized which can be controlled by the molecular structure of the monomeric precursors, A helix-like, cylindric structure of the chiral J-aggregates is suggested, The results expose an interesting model for studying and understanding enantioselective processes in the biosphere.