New class of easily-synthesisable and modifiable organic materials for applications in luminescent devices

New class of cheap, easily-synthesisable and modifiable organic luminescent materials is presented. 1,2-phenylenediboronic acid reacts with 8-hydroxyquinoline in high yield, both in solution and under mechanochemical conditions, and forms a brightly luminescent complex (emission maxima c.a. 500 nm (solid state) – 525 nm (solution)). This very first luminescent boronic 8-oxoquinoline complex exhibits emission lifetime of ns order, which, together with the DFT results, indicates a singlet-singlet origin of the fluorescence. The emission quantum yield, determined in acetonitrile is significant (c.a. 15%) and may be increased by choice of solvent. Additionally, the impact of the enhanced Lewis acidity of boron centres in the acid moiety was investigated on a series of the fluoro derivatives of 1,2-phenylenediboronic acid reacted with 8-hydroxyquinoline. In general, the mono-oxyquinolinato complex is preferably formed, however, in the case of the tetra-fluorinated acid a doubly-coordinated complex is stable and favourable. Interestingly, all of the fluorinated complexes exhibit highly comparable luminescent properties to the parent complex. Importantly, the obtained complexes appeared to be electroluminescent, thus a working OLED was successfully produced and tested.