Kinetically Inert Lanthanide Complexes as Reporter Groups for Binding of Potassium by 18-crown-6

Abstract

The barcode-like spectrum of lanthanide-centered emission has been used in imaging and to make responsive luminescent reporters. The intensities and the shapes of each line in the luminescence spectrum can also report on the coordination environment of the lanthanide ion. Here, we used lanthanide-centered emission to report on the binding of potassium in an 18-crown-6 binding pocket. The responsive systems were made by linking a crown ether to a kinetically inert lanthanide binding pocket using a molecular building block approach. Specifically, an alkyne-appended Ln.DO3A was used as a building block in a copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) "click" reaction with azide-functionalized crown ethers. The resulting complexes were investigated using NMR and optical methods. Titrations with potassium chloride in methanol observing the sensititzed europium- and terbium-centered emissions were used to investigate the response of the systems. The molecular reporters based on aliphatic crown ethers were found to have strongly inhibited binding of potassium, while the benzo-18-crown-6 derived systems had essentially the same association constants as the native crown ethers. The shape of the lanthanide emission spectra was shown to be unperturbed by the binding of potassium, while the binding was reported by an overall increased intensity of the lanthanide-centered emission. This observation was contrasted to the change in spectral shape between propargyl-Ln.DO3A and the triazolyl-Ln.DO3A complexes. The solution structure of the lanthanide complexes was found to be determining for the observed physical chemical properties of these systems.

Shining light on the antenna chromophore in lanthanide based dyes

“…We have previously attributed this form of spectrum to complexes of flexible DO3A ligands that is ligands without a fourth coordinating pendant arm. 67 The acetate resonances between 280-200 ppm are clearly resolved the Tb.L spectrum. This indicates that an open form does not contribute significantly to the solution structure of this complex.…”

Synthesis of triethoxysilylated cyclen derivatives, grafting on magnetic mesoporous silica nanoparticles and application to metal ion adsorption

“…Since the microwave approach was successful to synthesize L1-Boc the protocol was adapted for the synthesis of the derivative named L3-t Bu, which could not be obtained through standard approaches. Thereby precursor 5 (see ESI † for the synthesis of 5), 32 the silylated azide and 12 mol% of catalyst were dissolved in dry THF and stirred under microwaves at 100 C (200 Wmax) for 4 cycles of 10 min (Scheme 3). This new cyclen derivative was then identied by 1 H NMR, 13 C NMR, 29 Si NMR and HRMS.…”

APTRA‐Based Luminescent Lanthanide Complexes Displaying Enhanced Selectivity for Mg2+

“…Aw ide range of lanthanide complexes has been investigated, examining affinity and selectivity towards both cations (K + , Mg 2 + ,C a 2 + ,Z n 2 + ) [3][4][5][6] and anions( HCO 3 À ,F À ). [7,8] In most instances, the chromophore structure includes the ion binding domain and al uminescence change occurs on binding of the target ion.…”