Influence of Acetylation/Deacetylation on Aggregation-Induced Emission, Chirality and Self-Assembly Behavior of beta-D-Glucopyranoside-Tethered Naphthalene Diimide Amphiphiles

In this work, two naphthalene diimide (NDI) amphiphile, viz., NDI-P and NDI-D were synthesized by tethering acetylated and deacetylated beta-D-glucopyranoside respectively to the NDI via azide-alkyne click chemistry. Further, the effect of acetylation/deacetylation of the beta-D-glucopyranoside unit over fluorescence, chirality, self-assembly and aggregation induced emission (AIE) properties of NDI amphiphiles were investigated. The NDI-P aggregates exhibited cross-stacked pi-pi interaction, i.e., X-aggregation whereas NDI-D showed face-to-face pi-pi interaction i.e., H-aggregation in DMSO/H2O solvent mixture at higher volume % of water. Interestingly, NDI-P exhibited AIE behavior because of X-aggregation whereas, NDI-D could not overcome the aggregation-caused quenching (ACQ) and lost its fluorescence behavior completely. The chiral beta-D-glucopyranoside subunits also induced supramolecular chirality to the self-assembled NDI chromophores in DMSO/H2O solvent mixture at higher volume % of water. The induced circular dichroism (CD) was observed at wavelengths corresponding to their absorptions. Furthermore, the morphology of these amphiphiles was also governed by acetylation/deacetylation of beta-D-glucopyranoside moiety as the NDI-P self-assembled to form nanorod while NDI-D to the sphere at higher water fraction.