Emissive triphenylamine functionalised 1,8-naphthalimide and naphthalene diimide fluorophores: aggregation, computation and biological studies

Four new aromatic imides bearing triphenylamino (TPA) moieties are reported each of which differ by the number and/or positional arrangements of the TPA units. Compounds 1-3 are 1,8-naphthalimides (naps) that contain <i>N</i>,<i>N</i>'-diphenyl-[1,1'-biphenyl]-4-amino (TPA-Ph) groups appended to the <i>N</i>-termini of the respective imides. Each differs by their functionalisation of the 4-position of the nap: nitro (1), amino (2), or an additional TPA group (3). By contrast, compound 4 is a naphthalene diimide (NDI) functionalised with TPA-Ph moieties on each <i>N</i>-terminus. These simple modifications produce molecules with vastly different optoelectronic and aggregation properties. This article studies these characteristics with particular focus directed toward the contrast in aggregation-caused quenching (ACQ) properties of 2 compared with the aggregation-induced emission (AIE) properties of 3. The distinct aggregation and photophysical properties of 2 and 3 are delicately exploited using self-assembly with an amphiphilic poloxamer to generate nanoparticles capable of delivering 2 and 3 into cells for biological imaging.