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Bright mono-aqua europium complexes based on triazacyclononane that bind anions reversibly and permeate cells efficiently
journal contributionposted on 2015-09-15, 15:38 authored by Stephen ButlerStephen Butler, Brian K. McMahon, Robert Pal, David Parker, James W. Walton
A series of five europium(III) complexes has been prepared from heptadentate N5O2 ligands that possess a brightness of more than 10 mM−1 cm−1 in water, following excitation over the range λ=330–355 nm. Binding of several oxy anions has been assessed by emission spectral titrimetric analysis, with the binding of simple carboxylates, lactate and citrate involving a common ligation mode following displacement of the coordinated water. Selectivity for bicarbonate allows the rapid determination of this anion in human serum, with Kd=37 mM (295 K). The complexes are internalised quickly into mammalian cells and exhibit a mitochondrial localisation at early time points, migrating after a few hours to reveal a predominant lysosomal distribution. Herein, we report the synthesis and complexation behaviour of strongly emissive europium (III) complexes that bind oxy-anions in aqueous media with an affinity and selectivity profile that is distinctively different from previously studied systems.
We thank the ERC (FCC 266804) and CISbio Bioassys (J.W.W.) for support.