Probing the Effects of the Number and Positions of -OCH3 and -CN Substituents on Color Tuning of Ir(III) Complex Derivatives through a Joint Computational and Experimental Study.

Abstract

We performed a joint theoretical and experimental study on sixteen Ir(III) complexes bearing a similar molecular platform of bis(2-phenylbenzothiozolato-N,C2' ) iridium(III) (acetylacetonate) by grafting -OCH3 group and/or -CN group on different positions of the C-related arene moiety of the ligand (C-ring). Our results reveal that the introduction of -CN renders an overall drop in the FMO energy levels while a reverse increase is observed for -OCH3 . The ortho- and para-sites of the C-ring are more effective substitution positions to modulate the HOMO energy level due to the fact that the electronic density of HOMO mainly locates at them while the meta-site would induce a stronger impact on LUMO since the electronic density of LUMO mainly distributes over the position. Utilizing the synergistic effects of the substituents and the substituted positions, a wide color-tuning range from 479 nm to 637 nm was achieved, which covers nearly the whole window of visible spectrum. In particular, the tri-substituted Ir35mo4cn complex (λem max =637 nm) may be a potential candidate for high efficiency red OLEDs materials due to its greatly enhanced absorption processes, relatively higher 3 MLCT (%), lower ΔES1-T1 , enlarged separation between 3 MLCT/π-π* and 3 MC d-d states, and good hole and particle-transporting performances. Finally, six representative complexes were synthesized and their spectra were determined, which confirm the reliability of our computational strategy.