Tuning the Photophysical and Excited State Properties of Phosphorescent Iridium(III) Complexes by Polycyclic Unit Substitution.

Abstract

Two novel N‐embedded polycyclic units functionalized phosphorescent iridium(III) complexes (Ir‐1 and Ir‐2) with substituents in different positions have been prepared. Complex Ir‐1 bearing the substituent at the 3‐position shows a distinct blue shift single‐peak emission (524 nm) with a higher luminescence efficiency (ΦPL=42 %) and shorter emission lifetime (τ=282 ns) by comparison with 4‐position substitution based complex Ir‐2 (ΦPL=23 %, τ=562 ns), which exhibits a dual‐peak emission (564 nm and 602 nm), and phosphorescence color can be tuned from green to yellow. In addition, DFT calculations demonstrate that unusual ligand‐to‐metal charge transfer (3LMCT) excited state property can be found in Ir‐2, which is in contrast to metal‐to‐ligand charge transfer (3MLCT) excited state character in Ir‐1. This result can be attribute to strong electron‐donating character and 4‐position substitution effect of the unit.