The impact of the lanthanide contraction on the structure of complexes of a calix[4]arene trisamide

The syntheses of samarium, holmium, and ytterbium complexes of a tris-amide calix[4]arene are described, and the resulting structures are compared with the previously reported gadolinium complex. The syntheses involved the reaction of 5,11,17,23-tetra-tert-butyl-24-hydroxy-26,27,28- tris(diethylcarbamoylmethoxy)calix[4]arene with the appropriate lanthanide picrate hydrate. Structural studies demonstrated that a picrate anion acts as a quasi-bidentate ligand with Sm (and Gd), is unidentate in the Ho complex, but is found in the second coordination sphere for the smallest lanthanide cation (Yb) investigated

Phosphonate additives do not always inhibit crystallization

This paper investigates crystal growth modifiers based on 1,3,5-substituted benzene derivatives. The results show that as expected, the phosphonated derivative inhibits calcite precipitation to a much greater degree than the analogous sulfonate. However, on barium sulfate, both molecules show some crystallization promotion behaviour, with the phosphonate being the more potent promoter overall. Thus, the functional group alone does not determine the impact the organic molecule will have on crystallization. This opens the way for additives that have dual purposes (inhibiting the crystallization of one phase while not impacting or promoting the crystallization of other phases)

A "plug-and-play" approach to the preparation of transparent luminescent hybrid materials based on poly(methyl methacrylate), a calix[4]arene cross-linking agent, and terbium ions

A novel methodology to prepare transparent luminescent hybrid materials is reported. Using a calixarene ionophore as a PMMA cross-linker avoids problems, such as phase segregation, andproduces a polymer monolith that can be loaded with the metal ion required for luminescence post-synthesis. This approach is versatile and will simplify the production of such materials

PPARα and PPARγ activation is associated with pleural mesothelioma invasion but therapeutic inhibition is ineffective

Mesothelioma is a cancer that typically originates in the pleura of the lungs. It rapidly invades the surrounding tissues, causing pain and shortness of breath. We compared cell lines injected either subcutaneously or intrapleurally and found that only the latter resulted in invasive and rapid growth. Pleural tumors displayed a transcriptional signature consistent with increased activity of nuclear receptors PPARα and PPARγ and with an increased abundance of endogenous PPAR-activating ligands. We found that chemical probe GW6471 is a potent, dual PPARα/γ antagonist with anti-invasive and anti-proliferative activity in vitro. However, administration of GW6471 at doses that provided sustained plasma exposure levels sufficient for inhibition of PPARα/γ transcriptional activity did not result in significant anti-mesothelioma activity in mice. Lastly, we demonstrate that the in vitro anti-tumor effect of GW6471 is off-target. We conclude that dual PPARα/γ antagonism alone is not a viable treatment modality for mesothelioma

An azobenzene-based photoswitchable crystal growth modifier

An aspartic acid functionalised azobenzene derivative is found to be a light-switchable crystal growth modifier of calcite. UV irradiation of the molecule reversibly switches it to the cis isomer, which is a significantly less effective crystal growth inhibitor than the trans isomer. Visible light, or heat switches the inhibitor back “on”. Extended irradiation degrades the inhibitor such that it is irreversibly switched “off”. It was shown that the trans isomer is preferentially absorbed on to the crystal surface, which is consistent with its greater efficacy as an inhibitor

X-ray crystal structures of nickel and cobalt alpha-hydroxyoxime-carboxylic acid synergist complexes

A reagent that has regularly found use in synergistic systems is LIX63, the active component of which is 5,8-diethyl-7-hydroxydodecan-6-oxime (LH). The use of LIX63 in conjunction with a carboxylic acid (RH) to synergistically extract metal ions and form mixed-ligand complexes was first reported in 1969. Given that both ligands are capable of deprotonation, it has long been of interest to ascertain which of them acts as the anion and which acts as the neutral (synergist)species. However, information on the species formed in this system has traditionally been limited to equilibrium studies and UV-visible analysis. In the present work, the X-ray crystal structures of ‘model’ cobalt and nickel synergist complexes, synthesised using a short chained (C8) analogue ofLIX63 hydroxyoxime and isobutyric acid, are presented and discussed. The complexes have been found to have the same structure wherein the two acid groups are present in the anionic form and are located cis to one another. The two chelated alpha-hydroxyoxime ligands are uncharged with the oxime nitrogen atoms located trans to one another. Intra-molecular hydrogen bonding between each carboxylate carbonyl group and a cis-adjacent oxime hydroxyl group is evident. Unlike the phenolic-based hydroxyoxime-metal complexes and the previously proposed structure, no intra-molecular hydrogen bonding between the hydroxyoxime ligands is apparent. These structures provide the first definitive structural elucidation of the types complexes able to be formed via synergistic solvent extraction utilising LIX63 and carboxylic acids