Real-time In Situ Imaging of Aggregation-induced Emission and Solvent-guided Morphogenesis of a “V-shaped” 4-amino-1,8-naphthalimide Tröger's Base Supramolecular Scaffold

Abstract

The influence of solvent polarity on the self-assembly processes and its effect on the morphological outcome of self-assembled aggregates is another domain that requires a comprehensive study. The present investigation aims to address these issues by employing a unique “V-shaped” luminogen (TBNap, N-(3-pyridyl)-4-amino-1,8-naphthalimide Tröger's base), where the two 1,8-naphthalimide units are nearly orthogonal to each other. The TBNap is synthesized in high yield and fully characterized using standard characterization methods, including X-ray diffraction analysis, which reveals distinctly different structural arrangements of TBNap crystallized as different solvates in various solvent media. Furthermore, due to its internal charge transfer nature, the TBNap exhibits positive solvatochromism and solvent-guided morphogenesis. Given the unique structure, TBNap displays aggregation-induced emission enhancement in THF-H<inf>2</inf>O medium and forms self-assembled fluorescent nanoaggregates as imaged using different microscopic imaging techniques such as scanning electron microscopy (SEM) and confocal fluorescence microscopy. Furthermore, the latter is employed to demonstrate the in situ real-time visualization of these fluorescent nanoaggregates formations in native conditions and correlate the morphological outcome with SEM imaging.