Facial and Meridional Isomers of Tris(bidentate) Ir(III) Complexes: Unravelling Their Different Excited State Reactivity

TL;DR

This study investigates how facial and meridional isomers of tris(bidentate) Ir(III) complexes differ in their excited state reactivity, affecting their performance in phosphorescent OLEDs, and introduces new insights into their deactivation pathways.

Contribution

First-principles analysis revealing distinct excited state reactivities and triplet deactivation pathways for facial and meridional Ir(III) isomers, including the first description for meridional forms.

Findings

Different triplet metal-centered deactivation pathways identified for isomers.

Meridional isomers exhibit unique excited state reactivity.

Proposed strategies for phosphor design based on isomer reactivity.

Abstract

The use of tris(bidentate) Ir(III) complexes as light active components in phosphorescent organic light-emitting diodes (PhOLEDs) is currently the state-of-the-art technology to attain long-lasting and highly performing devices. Still, further improvements of their operational lifetimes are required for their practical use in lighting and displays. Facial/meridional stereoisomerism of the tris(bidentate) Ir(III) architectures strongly influences their emissive properties and thereto their PhOLEDs performances and operational device stabilities. This work underpins at the first-principles level the different excited state reactivities of facial and meridional stereoisomers of a series of tris(bidentate) Ir(III) complexes, which is found to originate in the presence of distinct triplet metal-centered (3MC) deactivation pathways. These deactivation pathways are herein presented for the first time for the meridional isomers. Finally, we propose some phosphor design strategies.