Strong red-emission tetraphenylethene-based AIE-active π-conjugated push-pull chromophores

Abstract

Two red-emissive chromophores, TPE-pCN and TPE-mCN, featuring a tetraphenylethene core substituted with electronic push-pull groups, were rationally designed and synthesised. Both compounds exhibit distinct aggregation-induced emission (AIE), with negligible fluorescence in solution but pronounced red emission in aqueous mixtures, yielding quantum efficiencies up to 0.34. Density functional theory calculations and single-crystal X-ray analysis reveal twisted conformations and intramolecular charge transfer characteristics. Time-resolved fluorescence spectroscopy demonstrates similar radiative decay rates with aggregation formation, while non-radiative losses are suppressed. Solid-state emission and low-temperature spectra suggest excimer-like behaviour in the aggregated phase. A prototype OLED device incorporating TPE-pCN displays efficient red electroluminescence (CIE: 0.60, 0.33) and a low turn-on voltage. These findings underline the utility of molecularly engineered AIE luminogens for high-performance optoelectronic applications, particularly where bright and stable red emission is essential.