Bright Mono‐aqua Europium Complexes Based on Triazacyclononane That Bind Anions Reversibly and Permeate Cells Efficiently

Abstract

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 K(d)=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.

Anion Recognition in Water: Recent Advances from a Supramolecular and Macromolecular Perspective

“…The complex was used to quantify bicarbonate anions in human serum by means of a ratiometric analysis of the bright europium‐based luminescence 26. Vilar and co‐workers have coupled a Gd III complex with Zn II –dipicolylamine moieties to devise a pyrophosphate‐responsive magnetic resonance imaging (MRI) contrast reagent 11 27.…”

EuroTracker® dyes: design, synthesis, structure and photophysical properties of very bright europium complexes and their use in bioassays and cellular optical imaging

“…30,35,43,44 For example, the reversible intramolecular ligation of the sulphonamide nitrogen in [Eu.L 21 ] is a function of pH. This complex localizes well to the endoplasmic reticulum, an organelle that is in equilibrium with the cytosol, so the pH is equivalent.…”

Seven‐Coordinate Luminophores: Brilliant Luminescence of Lanthanide Complexes with C3v Geometrical Structures

“…[7][8][9] Various types of luminescent lanthanide complexes have been reported to date. [10][11][12][13][14][15][16][17][18][19][20][21] Lanthanide complexes with asymmetric coordination structures exhibit high emission quantum yields (Φff) and large radiative rate constants (kr). [22,23] Lanthanide complexes generally provide eightcoordinate square anti-prism structures that are categorized as D4d in point group theory (8-SAP, Figure 1a).…”