Dual-emissive complexes: Visible and near-infrared luminescence from bis-pyrenyl lanthanide(III) complexes

The syntheses and photophysical attributes of a range of dual-emissive lanthanide complexes are described. The simple ligand architecture is based upon a diethylenetriaminepentaacetic acid (DTPA) core and appended with two arninopyrenyl chromophores to yield the fluorescent free ligand L-pyr. Reaction of the ligand with Ln(tris-trifluoromethanosulfate) gave the mononuclear complexes Ln center dot L-pyr (Ln = Nd, Er, Yb). Luminescence studies revealed that the complexes were emissive in both the near-IR and UV-Vis, the latter resulting from pyrene localised emission (lambda(em) = 390 nm), the former from pyrene-sensitised emission of the lanthanide ion (lambda(ex) = 337 nm). Time-resolved measurements in the near-IR indicated that the number of coordinated solvent molecules for Nd and Yb was <1, confirming the proposed coordination mode of the octadentate L-pyr. The suitability of pyrene as a sensitiser for near-IR emitting lanthanides was further demonstrated in the rare observation of Er-III emission in a non-deuteriated protic medium. (C) 2007 Elsevier Ltd. All rights reserved.