2134/18777 Stephen Butler Stephen Butler Brian K. McMahon Brian K. McMahon Robert Pal Robert Pal David Parker David Parker James W. Walton James W. Walton Bright mono-aqua europium complexes based on triazacyclononane that bind anions reversibly and permeate cells efficiently Loughborough University 2015 Cell imaging Europium Luminescence Microscopy Serum bicarbonate Chemical Sciences not elsewhere classified 2015-09-15 15:38:04 Journal contribution https://repository.lboro.ac.uk/articles/journal_contribution/Bright_mono-aqua_europium_complexes_based_on_triazacyclononane_that_bind_anions_reversibly_and_permeate_cells_efficiently/9394628 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.