Comparison of Structural and Optical Properties for N‐Embedded Polycyclic and Non‐Embedded Cationic Phosphorescent Iridium(III) Complexes

摘要

> We designed and synthesized N‐embedded polycyclic based cationic iridium(III) complex Ir‐NO and non‐embedded complexes Ir‐N and Ir‐O . Single crystal structures indicate that the N‐embedded polycyclic unit in Ir‐NO exhibits a certain planarity and induces two interesting π–π‐stackings between 2,2′‐bipyridine moieties of one molecule and two polycyclic units of the other molecule, and their shortest intermolecular distances are both 3.24 ?, which results in a stronger structural distortion of the 2,2′‐bipyridine ligand with a larger torsion angle (12.70°) in comparison with those of Ir‐N (5.51°) and Ir‐O (8.11°). Unpredictably, both Ir‐N and Ir‐O show deep red emission in solution, whereas Ir‐NO exhibits no emission. However, all complexes show significant luminescence in their respective polystyrene (PS) films, and Ir‐NO displays a longer emission lifetime than those of Ir‐N and Ir‐O . DFT calculations reveal that unusual ligand‐to‐metal charge transfer ( 3 LMCT) excited state character can be found in Ir‐NO and Ir‐N , which is in contrast to the metal‐to‐ligand charge transfer ( 3 MLCT) excited state observed in Ir‐O .