Anti-cooperative supramolecular polymerization: a new K2-K model applied to the self-assembly of perylene bisimide dye proceeding via well-defined hydrogen-bonded dimers.

A perylene bisimide dye bearing amide functionalities at the imide positions derived from amino acid l-alanine and a dialkoxy-substituted benzyl amine self-assembles into tightly bound dimers by π-π-stacking and hydrogen bonding in chloroform. In less polar or unpolar solvents like toluene and methylcyclohexane, and in their mixtures, these dimers further self-assemble into extended oligomeric aggregates in an anti-cooperative process in which even numbered aggregates are highly favoured. The stepwise transition from dimers into oligomers can not be properly described by conventional K2-K model, and thus a new K2-K aggregation model has been developed, which interpretes the present anti-cooperative supramolecular polymerization more appropriately. The newly developed K2-K model will be useful to describe self-assembly processes of a plethora of other π-conjugated molecules that are characterized by a favored dimer species.