UV-visible and 1H−15N^1H-^{15}N NMR spectroscopic studies of colorimetric thiosemicarbazide anion sensors

Four model thiosemicarbazide anion chemosensors containing three N – H bonds, substituted with phenyl and/or 4-nitrophenyl units, were synthesised and studied for their anion binding abilities with hydroxide, fl uoride, acetate, dihydrogen phosphate and chloride. The anion binding properties were studied in DMSO and 9 : 1 DMSO – H 2 O by UV-visible absorption and 1 H/ 13 C/ 15 N NMR spectroscopic techniques and corroborated with DFT studies. Signi fi cant changes were observed in the UV-visible absorption spectra with all anions, except for chloride, accompanied by dramatic colour changes visible to the naked eye. These changes were determined to be due to the deprotonation of the central N – H proton and not due to hydrogen bonding based on 1 H/ 15 N NMR titration studies with acetate in DMSO- d 6 – 0.5% water. Direct evidence for deprotonation was con fi rmed by the disappearance of the central thiourea proton and the formation of acetic acid. DFT and charge distribution calculations suggest that for all four compounds the central N – H proton is the most acidic. Hence, the anion chemosensors operate by a deprotonation mechanism of the central N – H proton rather than by hydrogen bonding as is often reported

Synthesis and prospective study of the use of thiophene thiosemicarbazones as signalling scaffolding for the recognition of anions

A family of phenyl-thiosemicarbazone dyes have been prepared and their interactions with anions monitorized via UV-Vis, fluorescence and 1H NMR titrations. Additionally quantum chemical calculations and electrochemical studies completed the studies carried out. The phenyl-thiosemicarbazone dyes show a modulation of their hydrogen-bonding and electron-donating capabilities as a function of the chemical groups attached and display two different chromo-fluorogenic responses towards anions in acetonitrile solutions. The more basic anions fluoride and cyanide are able to induce the dual coordination-deprotonation processes for all the receptors studied, whereas acetate only interacts with receptors 2, 3, 6, 7, 8, 9 and dihydrogen phosphate displays sensing features only with the more acidic receptors 6. Coordinative hydrogen bonding interactions is indicated by a small bathochromic shift, whilst deprotonation results in the appearance of a new band at ca. 400-450 nm corresponding to a colour change from colourless-yellow to yellow-red depending on the receptor. In the emission fluorescence, hydrogen bonding interaction is visible through the enhancement of the emission band, whereas deprotonation induced the growth of a new red-shifted emission. The chromo-fluorogenic behaviour could be explained on the basis of the deprotonation tendency of the binding sites and the proton affinity of the anions. PM3 and 1H NMR calculations are in agreement with the existence of the dual complexation-deprotonation process, whereas both studies are in discrepancy in relation to which is the proton involved in the deprotonation. Electrochemical studies carried with receptor 3 showed a quite complex redox behaviour and anodic shifts of the reduction peaks in the presence of the basic anions fluoride, cyanide and acetate.Fundação para a Ciência e a Tecnologia (FCT

Effects of metformin and donepezil on the prevention of doxorubicin-induced cardiotoxicity in breast cancer: a randomized controlled trial

Abstract Doxorubicin (DOX) causes deleterious cardiotoxicity. We aimed to investigate the protective roles of metformin and donepezil against DOX-induced cardiotoxicity. In this randomized-controlled trial, 143 female breast cancer patients were enrolled. Metformin (n = 43), donepezil (n = 52), or placebo (n = 48) were prescribed during DOX treatment. The primary endpoint was a proportion of patients with high sensitivity troponin-I (hsTnI) more than the 99th percentile value (> 15.6 ng/L) after DOX treatment. The secondary outcomes were the changes in the hsTnI, N-terminal pro-B-type natriuretic peptide (NT-proBNP), left ventricular ejection fraction (LVEF), global longitudinal strain (GLS) and peripheral blood mononuclear cells analysis for mitochondrial respiration. Baseline characteristics were similar between the groups. The primary endpoint occurred in 58.54% of metformin group, 76.92% in donepezil group, and 69.77% in placebo group (p = 0.215). The level of hsTnI increased after receiving DOX with subsequent decline in LVEF and GLS. Metformin and donepezil did not attenuate hsTnI elevation, LVEF or GLS reduction. There was no significant change in NT-proBNP level. Mitochondrial respiratory dysfunction was observed in the placebo and donepezil groups. However, metformin preserved mitochondrial respiration during DOX therapy. In conclusion, co-treatment with metformin or donepezil did not prevent myocardial injury. Metformin had a favorable mitochondrial outcome and warranted future studies

Urea Host Monomers for Stoichiometric Molecular Imprinting of Oxyanions

Synthesis and characterisation of a novel MIP and application as HPLC stationary phase for the selective analysis of model oxyanions and methotrexate. The innovative substructure approach and stoichiometric imprinting approach are used, to strongly reduce the aspecific binding. Sintesi di un nuovo polimero specifico e applicazione quale fase stazionaria cromatografica per l’ analisi qualitativa cromatografica (riconoscimento altamente specifico) di ossianioni modello e di metotrexato. Metodo innovativo del substructure imprinting e dello stoichiometric imprinting, forte riduzione del legame aspecifico

Mix and match : templating chiral Schiff base ligands to suit the needs of the metal ion

One-pot reactions of 2,2′-bipyridine-6-carbaldehyde, (1S,2S)-(−)-1,2-diphenyl-1,2-diaminoethane and FeCl2·4H2O or Zn(OAc)2·2H2O (2[thin space (1/6-em)]:[thin space (1/6-em)]1[thin space (1/6-em)]:[thin space (1/6-em)]1) at room temperature in MeOH lead to [Fe{(S,S)-5}2][PF6]Cl or [Zn{(S,S)-5}2][PF6]2 in which (S,S)-5 contains an imidazolidine ring, produced by intramolecular cyclization. This has been confirmed with the single-crystal structure of 2{P-[Fe{(S,S)-5}2][PF6]Cl}·H2O. The diastereoselectivity observed in the solid state has been confirmed by NMR spectroscopy for solutions of [Fe{(S,S)-5}2][PF6]Cl and [Zn{(S,S)-5}2][PF6]2. At room temperature, a minor product competes with the formation of [Fe{(S,S)-5}2][PF6]Cl, and the preference for these complexes is switched by carrying out the reaction in MeOH at reflux. In this case the major product is M-[Fe2{(S,S)-4}2][PF6]4 in which (S,S)-4 is the hexadentate Schiff base ligand formed by condensation of two equivalents of 2,2′-bipyridine-6-carbaldehyde with (1S,2S)-(−)-1,2-diphenyl-1,2-diaminoethane; the single-crystal structure of 4{M-[Fe2{(S,S)-4}2][PF6]4}·8Me2CO·5MeCN·3H2O confirms the assembly of a double helicate. When pyridine-6-carbaldehyde replaces 2,2′-bipyridine-6-carbaldehyde in the iron(II)-templated reaction with (1S,2S)-(−)-1,2-diphenyl-1,2-diaminoethane, the product is [Fe{(S,S)-7}2][PF6]2 (3[thin space (1/6-em)]:[thin space (1/6-em)]2 mixture of diastereoisomers in solution) in which (S,S)-7 is an asymmetrical Schiff base, formed by reaction of only one of the amine groups in (1S,2S)-(−)-1,2-diphenyl-1,2-diaminoethane. The solid state structure of P-[Fe{(S,S)-7}2][PF6]2·MeCN is presented