Sensitized near-infrared luminescence of lanthanide complexes by energy transfer from a ruthenium antenna

The luminescent ruthenium tetrapyrido [3, 2-a:2′, 3″-c:3″, 2″-h:2‴, 3‴-j] phenazine(tpphz) complex acts as a potential bridging ligand with a vacant diimine site, and is used as ‘metallo ligand’ to make heterodinuclear d–f complexes by attachment of a {Ln(dik)3} fragment (dik = tta (trifluoro theonyl acetone)) at the vacant site. When Ln = Nd, Yb or Er, the lanthanide centre has low-energy f–f excited states capable of accepting energy from the 3MLCT excited state of the Ru(II) centre. Luminescence quenching of the 3MLCT Ru(II) center affords sensitized Ln(III) based luminescence in the near-IR region. Nd(III) is found to be the most effective quencher for the 3MLCT luminescence of the ruthenium component because of the high density of f–f excited states of the appropriate energy, which makes it a more efficient energy-acceptor compared to the Er and Yb complexes.

Three d–f dyads have been prepared, in which Ru(II) polypyridine-type chromophores are connected to a Ln(III) centre via the tetrapyridophenazine(tpphz) bridging ligand. The luminescent Ru(II) complex acts as a “metallo ligand”, allowing the formation of Ru(II)–Ln(III) heterodinuclear complexes by the addition of a Ln(tta)3 unit at the second diimine site.Figure optionsDownload as PowerPoint slide