Exploiting an unexpected reactivity of cyclometalated iridium dimers for the direct synthesis of [Ir(C^N)2(O^CN)] complexes

Here we present the exploitation of the mechanism of the unexpected reactivity of μ-dichloro-bridged dimeric complex with formula [Ir(C^N)2Cl2] for the direct synthesis of [Ir(C^N)2(OC^N)] complexes (named JTG). JTG is an octahedral iridium complex with three cyclometalating ligands in meridional structure, where C^N indicates 2-phenylpyridyl and OC^N indicates that a oxygen is inserted between carbon from the 2-phenylpyridyl and center iridium ion. A series of synthesis conditions were investigated to understand the formation of the JTG. During the research process, the formation of meridional [Ir(C^N)3] was found (named JTO), which has an extremely similar structure with JTG, but with different emission color. The reaction yields of JTG were quite low, and it was accompanied by by-products that were difficult to purify. However it was possible to collect pure JTG by means of NMR spectroscopy. The electrochemical and photophysical characterizations of JTG and JTO are also reported. The presence of [OC^N] ligand results in a 80 mV shift to lower positive potentials. For the photophysical properties, the emission wavelength of JTG and JTO are virtually different (i.e. 535nm and 610nm respectively), the [OC^N] ligand enhances the lifetime corresponding to phosphorescent emission, the non-radiative decay still dominates, leading to the relatively lower PLQY and lifetime.