A Two‐Dimensional Coordination Compound as a Zinc Ion Selective Luminescent Probe for Biological Applications

Abstract

A 2D coordination compound {[Cu2(HL)(N3)]ClO4}infinity (1; H3L = 2,6-bis(hydroxyethyliminoethyl)-4-methyl phenol) was synthesized and characterized by single-crystal X-ray diffraction to be a polymer in the crystalline state. Each [Cu2(HL)(N3)]+ species is connected to its adjacent unit by a bridging alkoxide oxygen atom of the ligand to form a helical propagation along the crystallographic a axis. The adjacent helical frameworks are connected by a ligand alcoholic oxygen atom along the crystallographic b axis to produce pleated 2D sheets. In solution, 1 dissociates into [Cu2(HL)2(H3L)]2H2O (2); the monomer displays high selectivity for Zn2+ and can be used in HEPES buffer (pH 7.4) as a zinc ion selective luminescent probe for biological application. The system shows a nearly 19-fold Zn2+-selective chelation-enhanced fluorescence response in the working buffer. Application of 2 to cultured living cells (B16F10 mouse melanoma and A375 human melanoma) and rat hippocampal slices was also studied by fluorescence microscopy.

Imaging mobile zinc in biology

“…Despite limited water solubility, this system could detect exogenous zinc in mammalian cells. Sensors based on other fluorophores requiring UV excitation were recently reported and tested in biological systems at a proof-of-concept level [18–20]. …”

Phosphorescent Sensor for Biological Mobile Zinc

“…31 Various zinc-specific receptors have been developed in order to tune the p K a 32–38 and zinc dissociation constant ( K d ) of the sensor, 39–43 representative examples of which include DPA (di(2-picolyl)amine), DPEN ( N , N -di(2-picolyl)ethylenediamine), TRPEN ( N , N , N′ -tris(2-picolyl)ethylenediamine), quinoline, 2,2′-bipyridine, polyalkylamine, and iminodiacetate. 44 Conjugating these zinc-specific receptors onto fluorescent chromophores such as fluorescein, 32–35,41,42,45–55 coumarin, 56,57 quinoline, 31,58–63 and 4-nitrobenzo-oxadiazole 64–66 has produced a variety of fluorescence turn-on 31,32,47,49,52,63,65–85 and ratiometric sensors. 49,56,61,86–110 Despite their attractive features, fluorescent zinc sensors have some significant drawbacks, especially intrinsic signal contamination by autofluorescence and scattered light, which increases background and diminishes signal fidelity.…”

Synthesis, characterization, and fluorescence properties of dinuclear cadmium(II) complexes

“…Binucleating ligands are widely used to form dinuclear and multinuclear complexes. Our group has recently explored binucleating ligands prepared by reaction between 4-methyl-2,6-diformylphenol and respective amine to form multinuclear metal complexes [20][21][22].…”