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

5 years ago

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

Joseph Beames, James A. Platts, Simon J. A. Pope, Lara M. Groves, Duncan L. Browne, Peter N. Horton, Christiane Schotten, Simon J. Coles

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 IrIII 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 %. Complex Automation: A hybrid approach incorporating continuous-flow and microwave techniques to produce iridium-based phosphors with tunable luminesence and redox properties is reported. Synthesis times are significantly shortened and safety aspects are improved through this method. The novel series of pyrazole-iridium complexes were characterised by physical, photophysical and DFT methods and show tunability in their exhibited properties.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701551