Sensitization of Lanthanide Luminescence in Heterotrinuclear PtLn2 (Ln = Eu, Nd, Yb) Complexes with Terpyridyl-Functionalized Alkynyl by Energy Transfer from a Platinum(II) Alkynyl Chromophore

The preparation and characterization of the mononuclear complexes cis-Pt(dppe)(C⋮CPhtpy)2 (1) and cis-Pt(dppp)(C⋮CPhtpy)2 (5) (dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane, HC⋮CPhtpy = 4‘-(4-ethynylphenyl)-2,2‘:6‘,2‘ ‘-terpyridine) and the corresponding PtLn2 (Ln = Eu, Nd, Yb) heterotrinuclear complexes by incorporating the precursor 1 or 5 with Ln(hfac)3(H2O)2 are described. 1 and 5 exhibit intense, long-lived room-temperature phosphorescence, originating probably from an admixture of 3ILCT (π → π*(C⋮Cphtpy)) and 3MLCT (d(Pt) → π*(C⋮CPhtpy)) triplet states, which qualifies them as favorable energy donors to facilitate Pt → Ln energy transfer in the corresponding PtLn2 heterotrinuclear complexes. As anticipated, sensitized lanthanide luminescence in PtLn2 heterotrinuclear complexes is attained through efficient energy transfer from PtII alkynyl chromophore based 3MLCT and 3ILCT triplet states.