Preparation, characterization, and photophysical properties of Pt-M (M = Ru, Re) heteronuclear complexes with 1,10-phenanthrolineethynyl ligands.

When 3-ethynyl-1,10-phenanthroline (HCCphen) or 3,8-diethynyl-1,10-phenanthroline (HCCphenCCH) 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((t)Bu3tpy)(2+) units to the mononuclear Ru(II) or Re(I) precursor through platinum acetylide sigma 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 (3)MLCT excited states occurs because of less efficient intercomponent Pt --> Re energy transfer in the Pt-Re heteronuclear complexes.