Sensitized EuIII luminescence through energy transfer from PtM2 (M = Ag or Au) alkynyl chromophores in PtM2Eu2 heteropentanuclear complexes

Abstract

Using phosphorescent PtM₂ (M = Ag or Au) heterotrinuclear complexes with ethynyl-functionalized 2,2′:6′,2′′-terpyridyl ligands as precursors, PtM₂Eu₂ heteropentanuclear complexes were synthesized with 2,2′:6′,2′′-terpyridyl bound to a Eu^III ion. Upon excitation of the PtM₂ chromophore at 390 nm ≤ λ_ex ≤ 450 nm, the PtM₂Eu₂ complexes exhibit intense Eu-based luminescence sensitized through intramolecular d → f energy transfer, and the phosphorescence due to the PtM₂ chromophore is largely quenched. By the successive insertion of phenylene and ethynyl between acetylide and 2,2′:6′,2′′-terpyridyl in the bridging ligands, the rate and efficiency of d → f energy transfer are tunable. In contrast with the quite effective d → f energy transfer in the Pt–CCC₆H₄tpy–Eu arrays, the long-range energy transfer across Pt–CCC₆H₄CCC₆H₄tpy–Eu arrays becomes less efficient.