High-yielding synthesis of cyclometallated iridium complexes with hydrogen-bond rich ligands

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University of New Brunswick


Pseudooctahedrally coordinated t2g6 metals, namely cyclometalated iridium (III) complexes with C^N chelating ligands, have been widely designed and tested to improve the performance of organic light emitting diodes (OLEDs), chemical sensors and bioimaging labels. This is owing to their photophysical properties, i.e., photoluminescence quantum yield (PLQY), photo- and thermostability and tunability. Recently, Balónová et al. reported a series of complexes featuring ligands with H-bonding motifs (guanidine- and thiourea-like molecules). Such molecules are promising candidates for applying Ir(III) complexes in theranostics, in addition to the technologies given above. However, these H-bond rich ligands tend to self-recognize (and aggregate), leading to low solubility in most organic solvents and poor synthetic yields. Outlined in this thesis is an alternative synthetic strategy towards a library of cyclometalated Ir(III) complexes with H-bond rich ligands. Importantly, this strategy successfully circumnavigates the issue of ligand self-aggregation. In addition to standalone monomeric complexes, this de novo strategy was also used to generate a series of dimeric Ir(III) complexes, which were fully characterized (including their photophysical properties and strength of H-bond binding). Due to their interesting photophysical properties, such materials – both monomers and dimers – are at the forefront of developments in novel emissive supramolecular structures, e.g., as bioimaging dyes/ anion transporters and as the chromatophore within the emissive layer of OLEDs. The research presented in this thesis combines principles of supramolecular chemistry with a more classical synthetic approach and optimization, thereby affording a library of novel cyclometalated Ir(III) complexes with H-bond rich ligands. On account of their novelty and inherent properties, these Ir(III) complexes are put forward as promising candidates for useful additions to multiple scientific sectors.