B- and N-embedded color-tunable phosphorescent iridium complexes and B-N Lewis adducts with intriguing structural and optical changes

Abstract

A novel family of B- and N-embedded phosphorescent iridium complexes has been prepared. Single crystal structures indicate that the B-embedded polycyclic unit exhibits better planarity than the N-embedded polycyclic unit, which leads to different π-π-stacking and electrical characteristics. More importantly, by controlling the number of boron or nitrogen atoms embedded, solution-processed OLED devices incorporating these emitters as emitting layers can achieve a phosphorescence color variation from green to deep red (638 nm) and show low-efficiency roll-off and turn-on voltage. In particular, the B-embedded complex Ir-BB shows good color purity with a narrow full width at half maximum (1211 cm−1) and CIE coordinates (0.67, 0.31) in the deep red light region. Notably, B-embedded iridium complexes can also react with two different Lewis bases (pyridine and DMAP) to form intriguing B-N Lewis adducts through different coordination modes. During this process, significantly different structural and optical changes are triggered by the structure and electronic properties of Lewis bases, as confirmed by X-ray crystallographic, 1H NMR and spectral analysis.