Design and Characterization of a New Phenoxypyridine–Bipyridine-Based Tetradentate Pt(II) Complex Toward Stable Blue Phosphorescent Emitters

TL;DR

A new platinum complex with a tetradentate ligand was developed for use in PhOLEDs, showing blue phosphorescence and high thermal stability.

Contribution

A novel Pt(II) complex with a tetradentate ligand was synthesized and characterized for potential use in stable blue PhOLEDs.

Findings

The complex exhibits bluish-green emission with maxima at 490 and 518 nm.

It shows high thermal stability with a decomposition temperature above 340 °C.

Emission is attributed to triplet ligand-centered and charge-transfer transitions.

Abstract

Although various phosphorescent organic light-emitting diodes (PhOLEDs) have been developed, their lifetimes remain shorter than those of fluorescent OLEDs. In this study, a novel Pt(II) complex featuring a tetradentate ligand composed of bipyridine and phenoxypyridine, referred to as LL-O, was synthesized and fully characterized to evaluate its potential as a dopant for PhOLEDs. Geometry-optimized calculations indicate that LL-O adopts a distorted square–planar structure around the Pt(II) center. The complex displays bluish-green emission with maxima at 490 and 518 nm. However, it exhibits a low photoluminescence quantum yield (4%), primarily due to a dominant non-radiative decay rate that surpasses the radiative decay rate. Natural transition orbital analysis reveals that the emission of LL-O originates from a combination of triplet ligand-centered (3LC), triplet ligand-to-ligand charge-transfer (3LL′CT), and triplet metal-to-ligand charge-transfer (3MLCT) transitions. This compound also demonstrates high thermal stability (decomposition temperature > 340 °C) and an appropriate HOMO energy level (−5.58 eV), making it suitable for use as a dopant in versatile PhOLEDs.

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