Organic Light-Emitting Diodes (OLEDs) and Light Emitting Electrochemical Cells (LECs) are of increasing interest due to their ability to serve as alternative light sources. The main emissive components of these devices are typically ionic transition metal complexes (iTMCs). Iridium (III) complexes are of particular interest due to their desirable photophysical properties such as high radiative quantum yields, relatively short excited-state lifetimes, and overall stability. As such, the potential for their use in OLEDs/LECs and as photodynamic therapy (PDT) agents has inspired vigorous research into the improvement and/or modification of existing protocols for the preparation of the iridium (III) complexes themselves. A common challenge in the class of reactions is the requirement for long reaction times (often greater than 24 hours reflux) followed by extensive isolation and purification steps. We have utilized a microwave reactor to bring our research into closer alignment with the tenets of green chemistry. As an extension of this effort, we have synthesized a library of heteroleptic, cationic iridium (III) transition metal complexes (Ir-iTMCs) using microwave heating, resulting in drastically reduced preparation times compared with conventional heating, increased purity, and percent yield as reported in the literature. Beginning with compounds of the general formula [Ir(pq)<sub>2</sub>(N,N)]<sup>+</sup> (pq= 2-phenylquinoline; N,N = cuproines), we have expanded the ligand scope and synthesized a range of novel complexes. We will discuss both the procedural details of our versatile synthetic protocol as well as the characterization and photophysical properties of selected complexes.

Microwave synthesis and photophysical characterization of novel heteroleptic iridium complexes containing polyaromatic C^N and N^N ligands

ACS Spring 2022

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