Cluster helicates: promising functional materials.

Cluster helicates are a new type of supramolecular architecture that consists of a metal cluster wrapped around by ligands arranged in a helical mode. This class of compounds combines the unique properties of metal clusters with the sophisticated chiral arrangement found in helicates. Therefore, these architectures show promising applications in the development of advanced materials with specific electronic, magnetic, optical, catalytic and biological properties.

Understanding the Factors That Influence the Antioxidant Activity of Manganosalen Complexes with Neuroprotective Effects.

Manganosalen complexes are a class of catalytic antioxidants with beneficial effects against different neurological disorders according to various in vitro and in vivo studies. The interest in the factors that determine their antioxidant activity is based on the fact that they are key to achieving more efficient models. In this work, we report a set of new manganosalen complexes, thoroughly characterized in the solid state and in solution by different techniques.

Nickel, copper, and zinc dinuclear helicates: how do bulky groups influence their architecture?

The ligand design factors that may influence the isolation of metallosupramolecular helicates or mesocates still deserve to be investigated. In this sense, dinuclear nickel(II), copper(II) and zinc(II) compounds were obtained by electrochemical synthesis using a family of five Schiff base ligands, HL ( = 1-5), derived from bisphenylmethane and functionalized with bulky -butyl groups in the periphery and ethyl groups in the spacer. Six of the new complexes were characterized by X-ray crystallography, thus demonstrating that the helicate structure is predominant in the solid state.

A Dinuclear Copper(II) Complex Electrochemically Obtained via the Endogenous Hydroxylation of a Carbamate Schiff Base Ligand: Synthesis, Structure and Catalase Activity.

In the present work, we report a neutral dinuclear copper(II) complex, [Cu(L)(OH)], derived from a new [N,O] donor Schiff base ligand L that was formed after the endogenous hydroxylation of an initial carbamate Schiff base HL coordinated with copper ions in an electrochemical cell. The copper(II) complex has been fully characterized using different techniques, including X-ray diffraction. Direct current (DC) magnetic susceptibility measurements were also performed at variable temperatures, showing evidence of antiferromagnetic behavior.

Enemies or Allies? Hormetic and Apparent Non-Dose-Dependent Effects of Natural Bioactive Antioxidants in the Treatment of Inflammation.

This review aims to analyze the emerging number of studies on biological media that describe the unexpected effects of different natural bioactive antioxidants. Hormetic effects, with a biphasic response depending on the dose, or activities that are apparently non-dose-dependent, have been described for compounds such as resveratrol, curcumin, ferulic acid or linoleic acid, among others. The analysis of the reported studies confirms the incidence of these types of effects, which should be taken into account by researchers, discarding initial interpretations of imprecise methodologies or measurements.

Desulfurization of thiosemicarbazones: the role of metal ions and biological implications.

Thiosemicarbazones are biologically active substances whose structural formula is formed by an azomethine, an hydrazine, and a thioamide fragments, to generate a RC=N-NR-C(=S)-NR backbone. These compounds often act as ligands to generate highly stable metal-organic complexes. In certain experimental conditions, however, thiosemicarbazones undergo reactions leading to the cleavage of the chain.

Effect of Magnetic Anisotropy on the H NMR Paramagnetic Shifts and Relaxation Rates of Small Dysprosium(III) Complexes.

We present a detailed analysis of the H NMR chemical shifts and transverse relaxation rates of three small Dy(III) complexes having different symmetries (, or ). The complexes show sizeable emission in the visible region due to F → H transitions ( = 15/2 to 11/2). Additionally, NIR emission is observed at ca.

Schiff Bases Functionalized with T-Butyl Groups as Adequate Ligands to Extended Assembly of Cu(II) Helicates.

The study of the inherent factors that influence the isolation of one type of metallosupramolecular architecture over another is one of the main objectives in the field of Metallosupramolecular Chemistry. In this work, we report two new neutral copper(II) helicates, [Cu(L)]·4CHCN and [Cu(L)]·CHCN, obtained by means of an electrochemical methodology and derived from two Schiff-based strands functionalized with ortho and para-t-butyl groups on the aromatic surface. These small modifications let us explore the relationship between the ligand design and the structure of the extended metallosupramolecular architecture.

Exploring the Biological Properties of Zn(II) thiosemicarbazone Helicates.

The design of artificial helicoidal molecules derived from metal ions with biological properties is one of the objectives within metallosupramolecular chemistry. Herein, we report three zinc helicates derived from a family of thiosemicarbazone ligands with different terminal groups, Zn(L)∙2HO , Zn(L)∙2HO and Zn(L), obtained by an electrochemical methodology. These helicates have been fully characterized by different techniques, including X-ray diffraction.

Two Synthetic Approaches to Coinage Metal(I) Mesocates: Electrochemical versus Chemical Synthesis.

We report two different approaches to isolate neutral and cationic mesocate-type metallosupramolecular architectures derived from coinage monovalent ions. For this purpose, we use a thiocarbohydrazone ligand, HL (), conveniently tuned with bulky phosphine groups to stabilize the M ions and prevent ligand crossing to achieve the selective formation of mesocates. The neutral complexes [Cu(HL)] (), [Ag(HL)] (), and [Au(HL)] () were prepared by an electrochemical method, while the cationic complexes [Cu(HL)](PF) (), [Cu(HL)](BF) (), [Ag(HL)](PF) (), [Ag(HL)](NO) (), and [Au(HL)]Cl () were obtained by using a metal salt as the precursor.

Hydrolysis of a carbamate triggered by coordination of metal ions.

The mechanism of carbamate activation promoted by different metal ions has been explored in this work. The reaction of the carbamate ligand HL with chloride metal salts (M = Ni, Cu, Zn, Cd) leads to the coordination of the metal ions to the ligand, causing hydrolysis of the systems. This self-immolation process results in mononuclear dihydrazone complexes, carbon dioxide and the release of alcohol species from the pendant groups of the carbamate ligand.

Comparative study of the antitumoral activity of phosphine-thiosemicarbazone gold(I) complexes obtained by different methodologies.

A series of phosphino-thiosemicarbazone gold(I) dinuclear complexes obtained by two different synthetic procedures have been prepared. All the compounds have been spectroscopically characterized including single crystal X ray diffraction analysis in some of cases. [Au(HL)Cl] (1), [Au(HL)]Cl (2) and [Au(HL)]Cl (3) have been prepared by chemical synthesis using a gold(III) salt as precursor; while [Au(L)] (4), [Au(L)]∙2CHCN (5) and [Au(L)] (6) have been isolated from an electrochemical synthesis (HL = 2-[2-(diphenylphosphanyl)-benzylidene]-N-R-thiosemicarbazone; HL: R = methyl, HL: R = methoxyphenyl, HL: R = nitrophenyl).

Effect of the Metal Ion on the Enantioselectivity and Linkage Isomerization of Thiosemicarbazone Helicates.

The effect of the metal ion and ligand design on the enantioselectivity and linkage isomerization of neutral cobalt and zinc bisthiosemicarbazone metallohelicates has been investigated in this work. The electrochemical synthesis has afforded the enantioselective formation of chirally pure cobalt helicates, and the ΛΛ isomer of a single enantiomer has been crystallized as only product for the cobalt methyl-substituted thiosemicarbazone helicate. Interestingly linkage isomers have been formed from zinc ethyl-substituted thiosemicarbazone helicate enantiomers for the first time.