Synthesis and luminescent properties of hetero-bimetallic and hetero-trimetallic Ru(ii)/Au(i) or Ir(iii)/Au(i) complexes

Abstract

A series of Ru(II) and Ir(III) based photoluminescent complexes were synthesised that incorporate an ancillary 2,2′-bipyridine ligand adorned with either one or two pendant N-methyl imidazolium groups. These complexes have been fully characterised by an array of spectroscopic and analytical techniques. One Ir(III) example was unequivocally structurally characterised in the solid state using single crystal X-ray diffraction confirming the proposed formulation and coordination sphere. These complexes were then transformed into their heterometallic, Au(I)-containing, analogues in two steps to yield either bi- or trimetallic complexes that integrate {Au(PPh₃)}⁺ units. X-ray diffraction was used to corroborate the solid state structure of the hetero bimetallic complex, based upon a Ru(II)–Au(I) species. The heterometallic complexes all displayed red photoluminescent features (λ_em = 616–629 nm) that were consistent with the parent Ru(II) or Ir(III) lumophores in each case. The modulation of the emission from the Ru(II)–Au(I) complexes was much more strongly evident than for the Ir(III)–Au(I) analogues, which is ascribed to the inherent differences in the specific triplet excited state character of the emitting states within each heterometallic species.