Triarylmethane (TRAM)-Based Aggregation-Induced Emissive Luminogen with Enhanced Oxidation Stability and Bio-Imaging Capability

Abstract

Fluorescent technologies are driving a sustainable, eco-friendly future by enhancing energy efficiency, reducing environmental impact, and promoting renewable resources. Recent efforts have focused on designing small molecules with tunable fluorescent behavior, with diverse heterocyclic molecules playing a key role. Traditional carbazole-derived fluorophores, while highly fluorescent in dilute solutions, often suffer from aggregation-caused quenching (ACQ) in high-concentration or aggregated states due to non-radiative decay pathways like π–π stacking. Additionally, the 3,6-positions of carbazole are prone to irreversible electrochemical dimerization and polymerization, limiting their use in organo-electronic materials. To address the emission quenching and oxidation vulnerability, we introduced new molecular rotors at these positions to enhance oxidation stability and restrict intramolecular motions in the aggregated state. We designed an AIEgen by appending distorted tetraphenyl ethene to the carbazole moiety, flanked by two dialkylmethane groups, using quinone-methide chemistry with FeCl₃ catalyst. The resulting luminogen, MAS-01, exhibited cyan emission in the solid-state with impressive aggregation-induced emission with a photoluminescence quantum yield of 20.54%. MAS-01 also demonstrated cytotoxic behavior against HeLa cells, with an IC₅₀ value of 4.64 µg/mL, indicating concentration-dependent anti-metastatic potential. The luminogen uniformly entered the cytoplasm and showed nuclear co-localization, highlighting its bio-imaging capabilities even at low concentrations.