Remote controlled supramolecular switching using a ring-substituted peri-naphthoindigo derivative†

Abstract

Unlike artificial self-assemblies, many biological systems often rely on indirect input for their adaptive structures and function. To reduce the stark differences with their natural counterparts, artificial self-assemblies should also operate with the help of indirect inputs for adaptation. In this article we have demonstrated this using a new ring substituted peri-naphthoindigo (BuPNI) dye. The dye showed improved solubility in non-polar solvents and different aggregation behaviour than the parent PNI. The new dye underwent a self-assembly process in non-polar solvents (MCH, toluene), and the aggregation behaviour was tuned with the help of different guests like TFA, C60 fullerene and TfOH. By interacting with the donor–acceptor pairs of the dye, TFA was able to change the intermolecular arrangement. The rearrangement was found to be different when TfOH was used as a guest. Similarly, C60 fullerene interacted with the aggregated dye and produced a charge-transfer complex in the excited state. The guest-induced supramolecular rearrangement was also studied remotely by making changes in an adjacent solvent layer via a diffusion method. Placing an acid-induced rearranged aggregate in an organic solvent over an aqueous solution allowed the expulsion of the acid via diffusion, which in turn freed the chromophore and regenerated the original aggregate. The situation was reversed by the addition of acid to the aqueous layer. Contrary to the typical processes of acid-induced supramolecular rearrangements, which are spectroscopically reversible but not chemically reversible, our concept is fully reversible as it did not produce any unwanted waste (salt) in the reverse step.