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1-Methyl-3-hydroxy-pyridin-2-one Complexes of Near Infra-Red Emitting Lanthanides: Efficient Sensitization of Yb(III) and Nd(III) in Aqueous Solution

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posted on 03.05.2010, 00:00 by Evan G. Moore, Jide Xu, Sheel C. Dodani, Christoph J. Jocher, Anthony D’Aléo, Michael Seitz, Kenneth N. Raymond
The synthesis, X-ray structure, solution stability, and photophysical properties of several trivalent lanthanide complexes of Yb(III) and Nd(III) using both tetradentate and octadentate ligand design strategies and incorporating the 1-methyl-3-hydroxy-pyridin-2-one (Me-3,2-HOPO) chelate group are reported. Both the Yb(III) and Nd(III) complexes have emission bands in the Near Infra-Red (NIR) region, and this luminescence is retained in aqueous solution (ΦtotYb ∼ 0.09−0.22%). Furthermore, the complexes demonstrate very high stability (pYb ∼ 18.8−21.9) in aqueous solution, making them good candidates for further development as probes for NIR imaging. Analysis of the low temperature (77 K) photophysical measurements for a model Gd(III) complex were used to gain an insight into the electronic structure, and were found to agree well with corresponding time-dependent density functional theory (TD-DFT) calculations at the B3LYP/6-311G++(d,p) level of theory for a simplified model monovalent sodium complex.