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Three new calixarene Tl(+) ionophores have been utilized in Tl(+) ion-selective electrodes (ISEs) yielding Nernstian response in the concentration range of 10(-2)-10(-6)M TlNO3 with a non-optimized filling solution in a conventional liquid contact ISE configuration. The complex formation constants (logβIL) for two of the calixarene derivatives with thallium(I) (i.e. 6.44 and 5.85) were measured using the sandwich membrane technique, with the other ionophore immeasurable due to eventual precipitation of the ionophore during these long-term experiments. Furthermore, the unbiased selectivity coefficients for these ionophores displayed excellent selectivity against Zn(2+), Ca(2+), Ba(2+), Cu(2+), Cd(2+) and Al(3+) with moderate selectivity against Pb(2+), Li(+), Na(+), H(+), K(+), NH4(+) and Cs(+), noting that silver was the only significant interferent with these calixarene-based ionophores. When optimizing the filling solution in a liquid contact ISE, it was possible to achieve a lower limit of detection of approximately 8nM according to the IUPAC definition. Last, the new ionophores were also evaluated in four solid-contact (SC) designs leading to Nernstian response, with the best response noted with a SC electrode utilizing a gold substrate, a poly(3-octylthiophene) (POT) ion-to-electron transducer and a poly(methyl methacrylate)-poly(decyl methacrylate) (PMMA-PDMA) co-polymer membrane. This electrode exhibited a slope of 58.4mVdecade(-1) and a lower detection limit of 30.2nM. Due to the presence of an undesirable water layer and/or leaching of redox mediator from the graphite redox buffered SC, a coated wire electrode on gold and graphite redox buffered SC yielded grossly inferior detection limits against the polypyrrole/PVC SC and POT/PMMA-PDMA SC ISEs that did not display signs of a water layer or leaching of SC ingredients into the membrane., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Solution-phase and solid-state structural studies indicate that the remarkable hydrogelation properties of a proline-functionalised calix[4]arene emerge as a result of extended helical structures formed via inclusion of a proline moiety in a neighbouring calixarene cavity.

Kidney stones are an ailment that affects many people globally. While kidney stones can sometimes be treated with simple dietary changes this does not solve all cases. Most kidney stones are comprised predominantly of calcium oxalate and there are few very options in terms of accepted treatments for patients who suffer from this reoccurring condition. This research investigates the use of additives, resorcin[4]arenes and calix[4]arenes functionalised with three different amino acids (lysine, aspartic acid and proline) and their impact on the nucleation, morphology and zeta potential of calcium oxalate in a synthetic urine environment. The resorcin[4]arene functionalised with aspartic acid showed the stabilisation of calcium oxalate dihydrate rather than calcium oxalate monohydrate typically observed. The calix[4]arenes functionalised with proline and lysine showed large impacts on the morphology of the crystals formed. Additionally, the additives show significant impacts on the zeta potential of the crystals formed. It was also discovered that all three additives show evidence of incorporation to different extents through the crystal. These impacts were only observed when the macrocycles functionalised with amino acids were present, as the free amino acids showed minimal impact. [ABSTRACT FROM AUTHOR]

Our interest in the potential of chiral tetramethoxy‐resorcinarene as agents for chiral recognition has led us to synthesise twelve distally‐bridged chiral resorcinarene crowns. The fascinating architecture of these partially‐enclosed chiral basket molecules is evident in the solid‐state structures which have been determined by single‐crystal X‐ray crystallography. Moreover, the enantiomers of these chiral resorcinarene crowns have been resolved via diastereomeric resolution, with the absolute configuration of the diastereomers being determined by X‐ray crystallography. This work enables further exploration of these enantio‐pure chiral baskets as possible chiral resolving agents. [ABSTRACT FROM AUTHOR]

Three novel C4 symmetric O-substituted derivatives of tetramethoxyresorcinarene were synthesised and characterised and the selective distal lithiation of these derivatives was investigated. Lithiation of the tetraethoxy derivative, followed by quenching with dimethyldisulfide selectively afforded the distal product in 36% yield after removal of unreacted starting resorcinarene. Lithiation of the MOM derivative produced the five possible lithiated products, with the mono being the major product; the distally substituted derivative being a minor product. The benzyloxyresorcinarene appeared to be unstable under the lithation conditions. These results suggest that the selectivity of the distal lithation reaction is heavily dependent on the O-substituents of the resorcinarene. [ABSTRACT FROM AUTHOR]

Calix[4]arenes functionalised at the upper rim with acidic amino acid residues are found to have a significant impact on the crystal growth of model mineral systems, calcium carbonate and barium sulphate. The aspartic acid derivative is found to be most efficacious, matching or exceeding the impact of commercial phosphonate-based scale inhibitors. In some cases, the modified morphologies are found to be similar to those induced by proteins isolated from biomineralised systems. [ABSTRACT FROM AUTHOR]

The field of low molecular weight supramolecular gels, also known as physical gels, has grown rapidly over the last decade. In these gels, small molecules (gelators) self-assemble through non-covalent interactions, usually into a network of fibres, to trap solvent. Many physical gels are responsive to stimuli and often these types of gels can be reversibly converted from gel to sol. These properties make them ideal candidates for investigation into a range of potential applications, including biomedical, smart materials, sensors and catalysts. This review provides an overview of macrocyclic compounds, particularly the calixarenes, that can form supramolecular gels. [ABSTRACT FROM AUTHOR]

The tetra-isopropyl ethers of calix[4]arene and p-t-butylcalix[4]arene have been isolated in the cone conformation, and structurally characterised as chloroform solvates. Thermogravimetric analysis demonstrated that the parent isopropylcalix[4]arene solvate is significantly more stable than the p-t-butylcalix[4]arene analogue, retaining the solvent up to a temperature of 125°C. It was found that the calix[4]arene ether sublimes at atmospheric pressure, and solvent-free crystals appropriate for structure determination were produced at reduced pressure. The p-t-butylcalix[4]arene ether was also isolated without solvent in the lattice, but in this case the calixarene was crystallised from acetone, as sublimation did not produce crystals of sufficient quality. [ABSTRACT FROM AUTHOR]

A versatile synthon with formyl and allyl groups at the upper rim of calix[4]arene has been synthesized in two steps. Selective formylation of 25,27-diallyloxy-26,28-dihydroxycalix[4]arene, along with the Claisen rearrangement of the allyl groups, was achieved by reaction with hexamethylenetetraamine (hexamine) in glacial acetic acid. A control reaction of the dipropyl analogue shows that the selective formylation takes place independently of the Claisen rearrangement. The crystal structure of the dimethylacetal derivative of 5,17-diformyl-11,23-diallylcalix[4]arene is reported. [ABSTRACT FROM AUTHOR]