Supramolecular Luminescent Lanthanide Dimers for Fluoride Sequestering and Sensing

Abstract

Lanthanide complexes (Ln = Eu, Tb, and Yb) that are based on a C 2 -symmetric cyclen scaffold were prepared and characterized. The addition of fluoride anions to aqueous solutions of the complexes resulted in the formation of dinuclear supramolecular compounds in which the anion is confined into the cavity that is formed by the two complexes. The supramolecular assembly process was monitored by UV/ Vis absorption, luminescence, and NMR spectroscopy and high-resolution mass spectrometry. The X-ray crystal structure of the europium dimer revealed that the architecture of the scaffold is stabilized by synergistic effects of the EuÀFÀEu bridging motive, p stacking interactions, and a four-component hydrogen-bonding network, which control the assembly of the two [EuL] entities around the fluoride ion. The strong association in water allowed for the luminescence sensing of fluoride down to a detection limit of 24 nm.

Fluoride Binding and Crystal‐Field Analysis of Lanthanide Complexes of Tetrapicolyl‐Appended Cyclen

“…Peaks corresponding to the hydrated complex and the fluoride adduct were found to have very similar diffusion coefficients suggesting that they are of comparable size. This contrasts with the aforementioned C 2 ‐symmetric system studied by Charbonnière and co‐workers, in which intermolecular forces were postulated to induce dimer formation in solution ,…”

“…When the aromatic group is indazole, hydrogen‐bonding interactions stabilise a binuclear system, in which two complexed lanthanide centres are linked by bridging fluoride: in this system, a log K a value of 13.0 was obtained for a 2:1 binding event ,. In a related quinoline‐based system, a 1:1 binding of fluoride with log K a 4.1 (at pH 6) was measured . The affinity of our C 4 ‐symmetric tetrapicolyl complexes for fluoride is comparable to these C 2 ‐symmetric systems.…”

“…The affinity of these complexes for fluoride is dramatically higher than in the tetraamide systems studied by us and other groups . However, large binding constants for fluoride have recently been reported for C 2 ‐symmetric singly charged europium complexes incorporating two aromatic donor groups and two carboxylic acid donors . When the aromatic group is indazole, hydrogen‐bonding interactions stabilise a binuclear system, in which two complexed lanthanide centres are linked by bridging fluoride: in this system, a log K a value of 13.0 was obtained for a 2:1 binding event ,.…”

Highly Luminescent Microporous Organic Polymer with Lewis Acidic Boron Sites on the Pore Surface: Ratiometric Sensing and Capture of F− Ions

“…Furthermore, the solid‐state 13 C CP/MAS NMR spectrum shows a moderate signal at 90 ppm assigned to C of the CC bond, suggests bonding of the triarylborane node and 4,4′‐diethynylbiphenyl linker (Figure 1). Other peaks ranging from 120–150 ppm can be assigned to the aromatic C atoms of phenyl rings,12a, 16 and the peak at 19 ppm to aliphatic methyl substituents of the phenyl rings 6a. 17 The presence of boron in BMOP was confirmed by X‐ray photoelectron spectroscopy (XPS).…”

Energy Transfer in Supramolecular Heteronuclear Lanthanide Dimers and Application to Fluoride Sensing in Water

“…In our quest to design efficient Ln‐based luminescent sensors for anions in solution, we designed the octadentate ligand L, which forms [LnL(H 2 O)]Cl complexes in the presence of LnCl 3 salts (Ln=Eu, Tb, Yb) in water. It was demonstrated that the introduction of fluoride anions into aqueous solutions of the hydrated monomer led to the formation of supramolecular [(LnL) 2 F] + dimers (Scheme ) . Spectroscopic evidence further demonstrated that the formation of the dimer was the result of a positive associative cooperative process .…”