Photochemical, thermal and spectroscopic studies of metal carbonyl complexes

Flash photolysis of CpMn(C0)3, CbFe(C0)3 and ArCr(C0)3 in alkane solvents, resulted m the immediate formation of the solvent substituted dicarbonyl species. The reactivity of these species were investigated by uv/vis flash photolysis studies and in the case of CpMn(C0)3 by tnr flash photolysis. The rate constants for the reaction of theses species with a variety of nucleophiles were determined and the thermodynamic parameters associated with these reactions were measured. The chelation reactions of chromium carbonyl complexes, containing multidentate ligands, were investigated by uv/vis and ir spectroscopy. These chelation reaction were seen to proceed via bridging intermediates, even in those cases where the initial complex was coordinated in a monodentate fashion. The crystal structures of a number of chromium and tungsten complexes were determined and correlated with their spectroscopic features

Non-trivial solution chemistry between amido-pyridylcalix[4]arenes and some metal salts

Mercury ion complexation reactions were carried out between 3 and various mercury(II) salts. 1H NMR studies showed that the role of solvent, the anion chosen and the initial reaction conditions were critical and that the formation of a “simple” mercury(II) complex was non-trivial. The mercury(II) ion can cause either (i) the formation of an ion-pair system, which have a characteristic doubling of all signals in the 1H NMR spectrum, (ii) a cleavage reaction to occur resulting in the reformation of the calix[4]arene diester compound 2, but only when the reaction is heated and (iii) “simple” mercury binding to the pyridine rings when the binding studies are carried out using NMR titration techniques. The electrochemistry results, on the same systems, show that the initial reaction involves the removal of the phenoxide protons followed by the resulting catalysis of the mercury species. This proton removal is not observed in the NMR spectra of any of the mercury reactions. It was also found that 3 could bind silver and zinc salts and was not selective for mercury(II) as was previously described

Copper(11) complex of a tridentate N-Donor ligand with unexpected Cu-H interaction

The new pyridineâamine ligand, meophdpa (bis(dipyridylmethyl)-4-methoxyaniline) was synthesised and reacted with copper(II) perchlorate. The X-ray crystal structure of the resulting complex revealed a monomeric copper(II) site, with the copper bound to the three ligand nitrogens in a relatively unusual meridional fashion, as well as a chloride and a water molecule. The sixth coordination site was, unexpectedly, occupied by a phenyl ring hydrogen atom. Graphical abstract A new pyridineâamine ligand has been prepared and its reaction with copper perchlorate characterised. An interesting phenyl-HâCu interaction was observed

Anti-Hypochlorite and Catalytic Activity of Commercially Available Moringa oleifera Diet Supplement

Aiming at the assessment of the pro-health, and especially anti-hypochlorite properties of Moringa oleifera species a representative, commercially available Moringaoleifera dietary supplement was used as a substrate for the preparation of aqueous Moringa extract. The anti-hypochlorite activity of the extract was assessed using the hypochlorite-specific coumarin-based fluorescence turn-off sensor, namely 7-diethylamino-coumarin-3-carboxylic acid (7-DCCA). This compound was synthesized via the Knoevenagel condensation of 4-diethylamino-2-hydroxybenzaldehyde with Meldrum’sacidandtheMoringaextractwasemployedasamediumandcatalyst. Moreover,thetotal phenoliccontent(TPC)aswellasthereactiveoxygenspecies(ROS)–scavengingabilityoftheaqueous Moringa extract were determined. The results obtained demonstrated the applicability of Moringa extract as an anti-hypochlorite agent. Additionally, the satisfactory yield of the 7-DCCA obtained suggests the usefulness of the extract as a catalyst and the reaction medium. The antioxidative potentialoftheextractwasnotablylowerthanthatofthestandard(TROLOX).DeterminationofTPC in 100 g of the dry weight (DW) of studied material revealed a high number of polyphones present

Wide-and narrow-rim functionalised calix[4]arenes: synthesis and characterisation

Functionalisation of calix[4]arene at both the wide and narrow rims leads to the formation of compounds containing bipyridyl, via an amide linkage, at the wide rim and having either a butyl chain, a benzyl group or an alkyl ester functionality at the narrow rim. All compounds were characterised using 1H and 13C NMR spectroscopies. Initial binding studies with Ru(bipy)2Cl2 are reported. Graphical abstract Functionalisation of calix[4]arene was carried out such that metal complexation could occur at both the wide and narrow rims, a rare occurrence in calixarene chemistry

Anti-Cancer Activity and Mutagenic Potential of Novel Copper (II) Quinolinone Schiff Base Complexes in Hepatocarinoma Cells

This study determined the cytotoxic, cyto-selective and mutagenic potential of novel quinolinone Schiff base ligands and their corresponding copper(II) complexes in human-derived hepatic carcinoma cells (Hep-G2) and non-malignant human-derived hepatic cells (Chang). Results indicated that complexation of quinolinone Schiff bases with copper served to significantly enhance cytotoxicity. Here, the complex of (7E)-7-(3-ethoxy-2-hydroxybenzylideamino)-4-methylquinolin-2(1H)-one (TV117-FM) exhibited the lowest IC50 value (17.9 μM) following 96 h continuous exposure, which was comparable to cisplatin (15.0 μM). However, results revealed that TV117-FM lacked cytoselectivity over non-malignant cells. Additionally, the complex was minimally effluxed from cells via Pglycoprotein (P-gp) and was shown to be non-mutagenic in the Standard Ames test. Furthermore, BrdU incorporation assays showed that it was capable of inhibiting DNA synthesis in a concentrationand time-dependent manner. However, inhibition was not as a consequence of DNA intercalation, as illustrated in electrophoretic mobility shift assays. Interestingly, it was shown that the ligand was capable of inhibiting the action of topoisomerase II, but this was lost following complexation. This indicated that the mechanism of action of the novel copper(II) complex was different from that of the parent ligand and suggests that TV117-FM may have a therapeutic role to play in the treatment of hepatocellular carcinoma. Studies are currently underway to elucidate the exact in vitro mechanism of action of this novel, metal-based anti-cancer agent

Photocontrol of Upper and Lower Rim Complexation of Neutral and Cationic Species by p-tert-butylcalix[4]arene Tetraethyl Ester

A number of sodium salt complexes of p-tert-butylcalix[4]arene tetraethyl ester, 1, were isolated both with and without upper-rim encapsulated solvent. Selective decomplexation of lower rim bound sodium cations and upper rim encapsulated solvent molecules could be successfully achieved using low pressure light sources. Oxidation of the counter anion at the lower rim of p-tert-butylcalix[4]arene tetraethyl ester triggered both the upper and lower rim decomplexation process. The extent of decomplexation at both rims is controlled both by the nature of the counter-anionic species at the lower rim and by the fate of the photoproducts generated. The calixarene host molecule, 1, remains intact during the decomplexation process

Anti-Hypochlorite, Antioxidant, and Catalytic Activity of Three Polyphenol-Rich Super-Foods Investigated with the Use of Coumarin-Based Sensors

The anti-hypochlorite activity of açaí (Euterpe oleracea Mart.), goji (Lycium barbarum L.) and schisandra (Schisandra chinensis) fruit extracts were assessed by determining the reactive chlorine species (RCS)-scavenging ability of these three “super-food” berries. In addition, the aqueous extracts obtained were employed as both the media and the catalyst in a green chemistry approach to the synthesis of a coumarin-based fluorescence turn-off sensor, which was then used for anti-hypochlorite activity testing. The aqueous extracts were also assessed for total phenolic content (TPC), using the Folin–Ciocalteu method, and the antioxidant activity using the ABTS+• assay. Moreover, the main water-soluble polyphenolic constituents of the extracts were identified by the HPLC-PDA-ESI-MS technique. Among the extracts tested, açaí demonstrated the highest anti-hypochlorite and antioxidant activities, while the highest TPC value was found for the goji extract. All extracts demonstrated modest catalytic activity as Knoevenagel condensation catalysts

Novel Calixarene-Schiff Bases that Bind Silver(I) Ion

Two novel calix[4]arene-Schiff base receptors have been synthesized. One of the new compounds has two pendant aldimines, while the second has been prepared by two-point attachment of a calixarene-dialdehyde onto a calixarene-diamine to form a “calix-tube”. Preliminary binding studies with AgClO4 show large complexation-induced shifts in 1H NMR positions

2-Benzoylspiro[1H-isoindole-1,3'-isochromene]-1',3,4'(2H,3'H)-trione

The title compound, C₂₃H₁₃NO₅, was isolated following irradiation of N-benzoylphthalimide in toluene. The bond lengths and angles are typical of a molecule of this kind, but the molecule itself is of some interest. The most challenging aspect of the refinement was to devise a model to cater for disorder in one part of the molecule