| Summary: | The luminescent Pt(II) complex [Pt(4,4′-tBu2-bipy){CC-(5-pyrimidinyl)}2] (1) was prepared by coupling of [Pt(4,4′-tBu2-bipy)Cl2] with 5-ethynyl-pyrimidine, and contains two pyrimidinyl units pendant from a Pt(II) bipyridyl diacetylide core; it shows luminescence at 520 nm which is typical of Pt(II) luminophores of this type. Reaction with [Ln(hfac)3(H2O)2] (hfac = anion of hexafluoroacetylacetone) affords as crystalline solids the compounds [1 · {Ln(hfac)3(H2O)}{Ln(hfac)3(H2O)2}] (Ln = Nd, Gd, Er, Yb), in which the {Ln(hfac)3(H2O)} unit is coordinated to one pyrimidine ring via an N atom, whereas the {Ln(hfac)3(H2O)2} unit is associated with two N atoms, one from each pyrimidine ring of 1, via N⋯HOH hydrogen-bonding interactions involving the coordinated water ligands on the lanthanide centre. Solution spectroscopic studies show that the luminescence of 1 is partly quenched on addition of [Ln(hfac)3(H2O)2] (Ln = Er, Nd) by formation of Pt(II)/Ln(III) adducts in which Pt(II)→Ln(III) photoinduced energy-transfer occurs to the low-lying f-f levels of the Ln(III) centre. Significant quenching occurs with both Er(III) and Nd(III) because both have several f-f states which match well the 3MLCT emission energy of 1. Time-resolved luminescence studies show that Pt(II)→Er(III) energy-transfer (7.0 × 107 M-1) is around three times faster than Pt(II)→Nd(III) energy-transfer (≈2 × 107 M-1) over the same distance because the luminescence spectrum of 1 overlaps better with the absorption spectrum of Er(III) than with Nd(III). In contrast Yb(III) causes no significant quenching of 1 because it has only a single f-f excited level which is a poor energy match for the Pt(II)-based excited state. © 2008 Elsevier Ltd. All rights reserved.
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