title: 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.
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Butler
authors.forename: Brian K
authors.initials: BK
authors.lastname: McMahon
authors.forename: Robert
authors.initials: R
authors.lastname: Pal
authors.forename: David
authors.initials: D
authors.lastname: Parker
authors.forename: James W
authors.initials: JW
authors.lastname: Walton
mesh_terms: D000838:Anions / Q000737:chemistry*; D001372:Aza Compounds / Q000737:chemistry*; D001639:Bicarbonates / Q000032:analysis* / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D005063:Europium / Q000032:analysis* / Q000737:chemistry*; D006801:Humans; D008024:Ligands; D049449:Luminescence; D010880:Piperidines / Q000737:chemistry*; D044967:Serum / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000838:Anions; D001372:Aza Compounds; D001639:Bicarbonates; D008024:Ligands; D010880:Piperidines; C482777:triazacyclononane; D019343:Citric Acid; D005063:Europium
keywords: cell imaging; europium; luminescence; microscopy; serum bicarbonate