Self-Assembly of a Chiral Pyrene-Bifuran-Imide Into Helical and Spherical Nanostructures.

Abstract

We report the solvent-dependent self-assembly of 1-Py2, a novel bifuran-imide building block functionalized with terminal pyrene units and an enantiopure, alanine-derived chiral side chain. In pure tetrahydrofuran, 1-Py2 exists as a monomer with no electronic circular dichroism (ECD) signal. Increasing the water content to 60% drives the formation of highly organized hierarchical helical fibers. These chiral assemblies exhibit a strong ECD signal, and cryo-TEM measurements reveal an internal layer spacing of 3.7 nm within the helical fibers, indicative of a tail-to-tail bilayer arrangement. Upon further increasing the water content to 70%, the ECD signal is abolished as the molecules transition into nanospheres, accompanied by a bathochromic shift to an orange-red photoluminescence. This divergent aggregation highlights the potential of bifuran-imides as a platform for divergent assemblies.