Functional group engineering in naphthalimides: a conceptual insight to fine-tune the supramolecular self-assembly and condensed state luminescence

• Published in: Nanoscale Vol. 11; no. 28; pp. 13233 - 13242
• Main Authors: Meher, Niranjan, Iyer, Parameswar Krishnan
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 28.07.2019
• Subjects: Agglomeration; Chemical compounds; Congeners; Crystallography; Emissions control; Fluorescence; Functional groups; NMR; Nuclear magnetic resonance; Self-assembly; Single crystals
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c9nr04593g

Engineering well-defined supramolecular fluorescent nano-architectures based on organic conjugated small molecules has been an essential scientific challenge. Herein, a library of sixteen naphthalimide congeners ( 1-15 and HNI ) has been strategically designed that unveils a conceptual insight into the functional group controlled condensed state emission and aggregation-induced enhanced emission (AIEE) in conventional strong aggregation-caused quenching (ACQ) active fluorophores. Along with the regulation of ACQ-to-AIEE transformation and tailoring of the condensed state emission, a simple yet potential design strategy of functional group engineering has been established for the first time to spontaneously generate and systematically tailor the supramolecular self-assembly of organic small molecules into highly defined nano-architectures. Single-crystal XRD analysis of six congeners revealed that, unlike the well-established electronic contribution of the functional groups in the molecularly dispersed state, the condensed state photophysical and morphological properties are dictated by the distinct intermolecular π-π stacking interaction of the planar aromatic core. This work demonstrates an unconventional influence of the functional motif in the condensed state that could emerge as a promising route to build a fluorescent supramolecular nanoassembly from non-fluorescent conjugated molecules for a variety of future applications. A simple synthetic tweak of functional group engineering has been unveiled to fine-tune the supramolecular self-assembly and condensed state photophysical properties in small molecular system with effective control on ACQ/AIEE regulation.