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

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.