Non-conjugated alkyl chain engineering to tune condensed state photophysical and supramolecular assembly properties

Abstract

Techniques utilizing strategic molecular engineering to develop well-defined supramolecular fluorescent nano-assemblies hold significant scientific interest. However, a significant drawback in their practical application is the undesirable aggregation-caused quenching (ACQ) phenomenon in traditional fluorescent compounds, which usually occurs in planar aromatic cores. Herein, a series of seven planar naphthalimide (NC) derivatives have been constructed by appending non-conjugated linear alkyl chains that effectively modulate their condensed state emission and supramolecular nano-assembly. Structural characterization through single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD) patterns indicates that the supramolecular nano-assemblies and their condensed state emission properties are intricately governed by the alkyl chain-driven intermolecular packing orientation. The steric constraints exerted by the non-conjugated linear alkyl chains appended to the NC core efficiently alter the intermolecular π–π stacking interactions of the planar aromatic core. The investigated role of linear alkyl chains in modulating the condensed state behavior of NC derivatives presents a conceptual insight and a promising avenue for constructing fluorescent nano-assemblies.