Sensitization of lanthanide luminescence by two different Pt → Ln energy transfer pathways in PtLn3 heterotetranuclear complexes with 5-ethynyl-2,2′-bipyridine

Abstract

Reactions of 5-[2-(trimethylsilyl)-1-ethynyl]-2,2′-bipyridine (Me₃SiCCbpy) with Pt(bpy)Cl₂ (bpy = 2,2′-bipyridine) and Pt(bpyCC–CCbpy)Cl₂ (bpyCC–CCbpy = bis(2,2′-bipyridin-5-yl)butadiyne) induced isolation of Pt(bpy)(CCbpy)₂ (1) and Pt(bpyCC–CCbpy)(CCbpy)₂ (5), respectively. Incorporating Ln(hfac)₃(H₂O)₂ (hfac = hexafluoroacetylacetone) with 1 or 5 gave the corresponding PtLn₂ (Ln = Nd (2), Eu (3), Yb (4)) or PtLn₃ arrays (Ln = Nd (6), Eu (7), Gd (8), Yb (9)). With excitation at 360 ≤ λ_ex ≤ 480 nm, which is the MLCT absorption region of the Pt(2,2′-bipyridyl)(acetylide)₂ chromophore, sensitized lanthanide luminescence is successfully attained by efficient Pt → Ln energy transfer from the Pt^II antenna chromophores. In contrast with quite efficient Pt → Ln energy transfer in the Pt–CCbpy–Ln (Pt⋯Ln = 8.6 Å) array, energy transfer transmitted across the Pt–bpyCC–CCbpy–Ln (Pt⋯Ln = 13.3 Å) array is less efficient owing to the much longer Pt⋯Ln separation in the latter.