Cross-Linking the Fibers of Supramolecular Gels Formed from a Tripodal Terpyridine Derived Ligand with d-Block Metal Ions.

The tripodal terpyridine ligand, L, forms 1D helical supramolecular polymers/gels in H2O-CH3OH solution mediated through hydrogen bonding and π-π interactions. These gels further cross-link into 3D supramolecular metallogels with a range of metal ions (M) such as Fe(II), Ni(II), Cu(II), Zn(II), and Ru(III); the cross-linking resulting in the formation of colored or colorless gels. The fibrous morphology of these gels was confirmed using scanning electron microscopy (SEM); while the self-assembly processes between L and M were investigated by absorbance and emission spectroscopy from which their binding constants were determined by using a nonlinear regression analysis.

Europium-directed self-assembly of a luminescent supramolecular gel from a tripodal terpyridine-based ligand.

Eu(III), the last piece in the puzzle: Europium-induced self-assembly of ligands having a C(3)-symmetrical benzene-1,3,5-tricarboxamide core results in the formation of luminescent gels. Supramolecular polymers are formed through hydrogen bonding between the ligands. The polymers are then brought together into the gel assembly through the coordination of terpyridine ends by Eu(III) ions (blue dashed arrow: distance between two ligands in the strand direction).

Selective and tuneable recognition of anions using C(3v)-symmetrical tripodal urea-amide receptor platforms.

The synthesis and binding investigations of first generation C(3v)-symmetrical hydrogen bonding urea-amide based tripodal receptors, 1-6, with various anions such as acetate, phosphate, sulfate and chloride in DMSO-d(6) are presented. Analysis of the (1)H NMR titrations of 1-6 showed on all occasions the selective formation of 1 : 1 stoichiometries.

The recognition of anions using delayed lanthanide luminescence: the use of Tb(iii) based urea functionalised cyclen complexes.

A cyclen based lanthanide luminescent sensor, , has been developed by taking advantage of a combination of hydrogen bonding and f-metal ion coordination binding sites for anionic species. Analysis of the ground state, the emission from the singlet and the Tb(iii) excited states clearly show the ability of the Tb(iii) complex to signal the presence of anions in CH(3)CN, through multiple binding interactions consisting of hydrogen bonding and metal coordination. The delayed lanthanide luminescence from the Tb(iii) diaryl-urea complex was found to be significantly enhanced only upon recognition of H(2)PO(4)(-), at the same time as displaying good selectivity over other competitive anions, such as CH(3)COO(-).

The recognition and sensing of anions through "positive allosteric effects" using simple urea-amide receptors.

The design, synthesis, and X-ray crystallographic analysis of three simple diaryl-urea based anion receptors possessing an amide moiety on one of the aryl groups, and an electron withdrawing CF(3) group on the other, is described. The three receptors differ only in the position of the amide functionality relative to the hydrogen bonding urea moiety (being para, meta, and ortho for 1, 2, and 3, respectively). This simple modification was shown to have a significant effect on the anion recognition ability, the strength of the recognition process, and the stoichiometry (host/guest) for these sensors.

Lanthanide luminescent anion sensing: evidence of multiple anion recognition through hydrogen bonding and metal ion coordination.

The delayed lanthanide luminescence of the terbium [Tb(III)] diaryl-urea complex 1xTb is significantly enhanced upon sensing of dihydrogenphosphate (H2PO4(-)) in CH3CN, which occurs through multiple anion binding through hydrogen bonding interactions and potential metal ion coordination to Tb(III).

pH driven self-assembly of a ternary lanthanide luminescence complex: the sensing of anions using a beta-diketonate-Eu(III) displacement assay.

The synthesis and the photophysical evaluation of a novel pH dependent lanthanide luminescent self-assembly in water between a cyclen based europium complex and a beta-diketonate is described and its use as a luminescent sensor in displacement assays for anions such as acetate, bicarbonate and lactate, where the Eu(III) emission was quenched upon anion recognition.

Fluorescent photoinduced electron transfer (PET) sensors for anions; from design to potential application.

This mini review highlights the synthesis and photophysical evaluation of anion sensors, for nonaqueous solutions, that have been developed in our laboratories over the last few years. We have focused our research mainly on developing fluorescent photoinduced electron transfer (PET) sensors based on the fluorophore-spacer-anion receptor principle using several anthracene (emitting in the blue) and 1,8-naphthalimide (emitting in the green) fluorophores, with the aim of targeting biologically and industrially relevant anions such as acetates, phosphate and amino acids, as well as halides such as fluoride. The receptors and the fluorophore are separated by a short methyl or ethyl spacer, where the charge neutral anion receptors are either aliphatic or aromatic urea (or thiourea) moieties.