A [Cyclentetrakis(methylene)]tetrakis[2-hydroxybenzamide] Ligand That Complexes and Sensitizes Lanthanide(III) Ions.

The synthesis of the cyclen derivative H(4)L(1)·2 HBr containing four 2-hydroxybenzamide groups is described. The spectroscopic properties of the Ln(III) conplexes of L(1) (Ln=Gd, Tb, Yb, and Eu) reveal changes of the UV/VIS-absorption, circular-dichroism-absorption, luminescence, and circularly polarized luminescence spectra. It is shown that at least two metal-complex species are present in solution, whose relative amounts are pH dependent. At pH > 8.0, an intense long-lived emission is observed (for [TbL(1)] and [YbL(1)]), while at pH < 8.0, a weaker, shorter-lived species predominates. Unconventional Ln(III) emitters (Pr, Nd, Sm, Dy, and Tm) were sensitized in basic solution, both in the VIS and in the near-IR, to measure the emission of these ions.