Low-temperature solvent-free synthesis route of blue and green luminescent phases of tris(8-hydroxyquinoline)aluminum (AlQ3)

Recent research studies have shifted towards simple, efficient, and more eco-friendly synthesis methods. The current study focuses on using a free-solvent reaction to synthesize trichelate 8-hydroxyquinoline (8HQ) octahedral Al(III) coordination complex (AlQ3), which still represents the most widely used electroluminescent material in organic light-emitting devices (OLEDs). We have developed a new safe and easy route for synthesizing AlQ3 via a pure solid-state reaction between 8HQ and AlCl3 with sodium carbonate as an inorganic base. The formation of the free-solvent prepared AlQ3 was confirmed using FT-IR, UV-Vis spectroscopy, SEM/EDS analysis, powder, and single crystal. Our investigation overturns the belief that fac-AlQ3 is only formed at high temperature; the developed synthesis method enabled the production of blue-fluorescent AlQ3 at room temperature. Furthermore, this study presents a low-temperature synthesis pathway for obtaining pure AlQ3 phases for the first time. We controlled the washing step of the isolated AlQ3 to produce large amounts of blue and green luminescent AlQ3. The optical properties of the samples were determined using photoluminescence (PL) spectroscopy.