Modulation of Luminescent Behaviour in N-Heterocyclic Thiones

Abstract

The development of pure organic emitters with precise color tunability is crucial for the wide range of light-emitting applications. However, achieving a high color purity along with high quantum yield and is a challenging task that demands precise molecular design. Here, we demonstrate the modulation and four-fold increment of quantum yield via N-substitution in an imidazopyridine-based crystalline material, [2-(2,4,6-trimethylphenyl) imidazopyridine-3-thione] (MPIT), [2-(2-diphenylmethyl-4,6-dimethylphenyl)imidazopyridine-3-thione] (DPPIT) and [2-(2,6-diphenylmethyl-4-methylphenyl) imidazopyridine-3-thione] (TPPIT). These materials can be prepared on a gram scale and thoroughly characterised using FT-IR, multinuclear NMR, HRMS, CV and SCXRD. The light-emitting properties of MPIT, DPPIT and TPPIT have been reported. The photophysical properties of these materials were investigated in solution and the crystalline state. In addition, these organosulfur compounds were studied using theoretical calculations. These materials demonstrated excellent photoluminescence quantum yield (> 50%) and substantial substitution contribution in DPPIT and TPPIT. The bluish-green fluorescence emission was observed with a lifetime of 17 ns, making them a potential candidate for light-emitting applications.