Bis-Cyclometallated Iridium(III) Complexes with Bidentate Ligands Containing One or Two Pyridylideneamine (PYE) Donors: Influence of PYE Substitution (para or ortho) on Complexation

Six pyridylideneamine (PYE)-containing bidentate ligands and their bis-cyclometallated Ir(III) complexes have been synthesised and fully characterised. The PYE groups show a contribution from a neutral imine resonance form and a zwitterionic pyridinium form. NMR spectroscopy of the para-substituted ligands and complexes show those with a C6H4 bridging group have the fastest PYE rotation. X-ray crystallography of p-1 and p-3 shows the PYE N-donor is trigonal planar whereas for the ortho-complexes it is more pyramidalized implying an increased contribution of the zwitterionic resonance form for the ortho-complexes.

Automated summary

Six bidentate ligands containing PYE groups and their bis-cyclometallated Ir(III) complexes have been synthesized and fully characterized. NMR spectroscopy showed that complexes with a C6H4 bridging group have the fastest PYE rotation. X-ray crystallography indicated that the PYE N-donor is trigonal planar in para-substituted complexes and more pyramidalized in ortho-complexes, suggesting an increased contribution of the zwitterionic resonance form in the latter.