Improved Deep-Red Phosphorescence in Cyclometalated Iridium Complexes via Ancillary Ligand Modification

29 October 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

In this work, we describe bis-cyclometalated iridium complexes with efficient deep-red luminescence. Two different cyclometalating (C^N) ligands‒1-phenylisoquinoline (piq) and 2-(2- pyridyl)benzothiophene (btp)‒are used with six strong π-donating ancillary ligands (L^X) to furnish a suite of 10 new complexes with the general formula Ir(C^N)2(L^X). Improvements in deep-red photoluminescence quantum yields were accomplished by the incorporation of sterically encumbering substituents onto the ancillary ligand, which can enhance the radiative rate constant (kr) and/or reduce the non-radiative rate constant (knr). Five of the complexes were characterized by X-ray crystallography, and all of them were investigated by in-depth spectroscopic and electrochemical measurements.

Keywords

Phosphorescence
Deep red emission
Cyclometalated iridium
ligand design
Photoluminescence

Supplementary materials

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Ir piq btp deep red SI
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