Unravelling the Interplay between Structure, Self-Assembly Patterns, AIEE and Chiroptical Properties of NDI-bis-Cholesteryl Systems

Abstract

Naphthalene Diimides (NDI) offer exquisite optical and electronic properties and find a broad range of applications in various chemical and biomedical fields. However, due to their flat structure, at higher concentrations, the emission from NDIs gets severely quenched. The restoration of luminescence in such interesting class of molecules have been widely explored through the tuning of their optical properties via synthetic modification, supramolecular self-assembly and aggregation induced emission (AIE) techniques. Here, we aim at highlighting the role of spacer group in the tuning of the chiroptical properties of NDI through self-assembly approach, using a bis-cholesteryl diimide system. The three NDI-bis-cholesteryl systems have been prepared and their self-assembled structures, optical and chiral properties in monomeric and aggregated states have been studied. Microscopic investigations reveal almost identicle morphology in aggregates, however, quite different aggregational behaviour and chiroptical properties in ground and excited state are observed. Circular dichroism (CD) studies revealed an interesting medium controlled enhancement and reversal of chiral properties in the self-assembled structures.