Preparation, Characterization, and Photophysical Properties of Pt−M (M = Ru, Re) Heteronuclear Complexes with 1,10-Phenanthrolineethynyl Ligands

When 3-ethynyl-1,10-phenanthroline (HCCphen) or 3,8-diethynyl-1,10-phenanthroline (HCCphenCCH) is utilized as a bifunctional bridging ligand via stepwise molecular fabrication, a series of Pt−Ru and Pt−Re heteronuclear complexes composed of both platinum(II) terpyridyl acetylide chromophores and a Ru(phen)(bpy)₂/Re(phen)(CO)₃Cl subunit were prepared by complexation of one or two Pt(^tBu₃tpy)²⁺ units to the mononuclear Ru^II or Re^I precursor through platinum acetylide σ coordination. These Pt−Ru and Pt−Re complexes exhibit intense low-energy absorptions originating from both Pt- and Ru (Re)-based metal-to-ligand charge-transfer (MLCT) states in the near-visible region. They are strongly luminescent in both solid states and fluid solutions with a submicrosecond range of lifetimes and 0.27–6.58% of quantum yields in degassed acetonitrile. For the Pt−Ru heteronuclear complexes, effective intercomponent Pt → Ru energy transfer takes place from the platinum(II) terpyridyl acetylide chromophores to the ruthenium(II) tris(diimine)-based emitters. In contrast, dual emission from both Pt- and Re-based ³MLCT excited states occurs because of less efficient intercomponent Pt → Re energy transfer in the Pt−Re heteronuclear complexes.