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Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging
Published on: July 21, 2011
A [Cyclentetrakis(methylene)]tetrakis[2-hydroxybenzamide] Ligand That Complexes and Sensitizes Lanthanide(III) Ions
Anthony D'Aléo1, Jide Xu, King Do
1Chemical Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, CA 94720, and Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA.
Abstract:
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.
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