Mechanosynthesis of solid-state benzoxazoles for use as OLED

There are several methods to synthesize precursor molecules to develop devices based on organic light emitting diodes. Among them, batch process using thermic energy on liquid phase (TELP) and mechanic energy on solid state (MESS). Last one is known as mecanosynthesis is a method characterized by favoring chemical reactions that require high transition energies. In this study, 9 benzoxazoles, organic heterocycles were synthesized in order to obtain materials with semiconductor and electroluminescent characteristics for the development of organic light emitting diodes (OLEDs) using TELP and MESS techniques. A Pulverisette 7 high-energy planetary ball mill was used with silicon-nitride (Si3N4) and stainless-steel jars and balls. After milling, the solid mixtures were isolated by filtration and washed with methanol (MeOH). Structures were confirmed by 1H NMR (Varian 400 MHz) and FT-IR (PerkinElmer Spectrum 100, ATR). Spectroscopic monitoring and UV observations indicated luminescent product formation at 365 nm (SS), 254 nm (MeOH), and 265 nm (water) solution. Reactions typically reached completion within 0.5–1.5 h, affording yields of 44–95%. Notably, switching from Si3N4 to stainless-steel milling media approximately halved the reaction time. Overall, mechanosynthesis provides an eco-efficient and practical route to electroluminescent materials by minimizing solvent use, shortening reaction times, and delivering yields comparable to or better than those obtained with conventional solution-phase methods.