From Ligand to Phosphor: Rapid, Machine-Assisted Synthesis of Substituted Iridium(III) Pyrazolate Complexes with...

A first-generation machine-assisted approach towards the preparation of hybrid ligand/metal materials has been developed. A comparison of synthetic approaches demonstrates that incorporation of both flow chemistry and microwave heating can be successfully applied to the rapid synthesis of a range of new phenyl-1H-pyrazoles (ppz) substituted with electron-withdrawing groups (-F, -CF₃ , -OCF₃ , and -SF₅ ). These, in turn, can be translated into heteroleptic complexes, [Ir(ppz)₂ (bipy)]BF₄ (bipy=2,2'-bipyridine). Microwave-assisted synthesis for the Ir^III complexes allows isolation of spectroscopically pure species in less than 1 h of reaction time starting from IrCl₃ . All of the new complexes have been characterised photophysically (including nanosecond time-resolved transient absorption spectroscopy), electrochemically, and by TD-DFT studies. The complexes exhibit ligand-dependent, tuneable, green-yellow luminescence (500-560 nm), with quantum yields in the range 5-15 %.