Reactivity of non-organometallic ruthenium(II) polypyridyl complexes and their application as catalysts for hydride transfer reactions

Recently, we investigated the substitution behavior of a series of ruthenium(II) complexes of the general formula [RuII(terpy)(N∧N)Cl]Cl, where terpy = 2,2′:6′,2″-terpyridine, N∧N = bidentate ligand, in aqueous solutions. We have shown that the most and least reactive complexes of the series are [RuII(terpy)(en)Cl]Cl (en = ethylenediamine) and [RuII(terpy)(phen)Cl]Cl (phen = 1, 10-phenantroline), respectively, as a result of different electronic effects provided by the bidentate spectator chelates. Polypyridyl amine Ru(II) complex, viz. [Ru(terpy)(en)Cl]Cl and [Ru(terpy)(ampy)Cl]Cl (where ampy = 2-(aminomethyl)pyridine), in which the terpy chelate labilizes the metal center, are able to catalyze the conversion of NAD+ to 1,4-NADH using sodium formate as a source of hydride. We showed that this complex can control the [NAD+]/[NADH] ratio and potentially induce reductive stress in living cells, which is accepted as an effective method to kill cancer cells. Polypyridyl Ru(II) complexes, characterized in terms of the behavior in aqueous solutions, can be used as model systems to monitor heterogeneous multiphase ligand substitution reactions at the solid-liquid interface. Colloidal coordination compounds in the submicron range were synthesized from Ru(II)-aqua derivatives of starting chlorido complexes via the anti-solvent procedure and stabilized by a surfactant shell layer.

Iron(II)-α-keto acid complexes of tridentate ligands on gold nanoparticles: the effect of ligand geometry and immobilization on their dioxygen-dependent reactivity

Two mononuclear nonheme iron(II)-benzoylformate (BF) complexes [(6Me₂-Me-BPA)Fe(BF)](ClO₄) (1a) and [(6Me₃-TPMM)Fe(BF)](ClO₄) (1b) of tridentate nitrogen donor ligands, bis((6-methylpyridin-2-yl)methyl)(N-methyl)amine (6Me₂-Me-BPA) and tris(2-(6-methyl)pyridyl)methoxymethane (6Me₃-TPMM), were isolated and characterized. The structural characterization of iron(II)-chloro complexes indicates that the ligand 6Me₂-Me-BPA binds to the iron(II) centre in a meridional fashion, whereas 6Me₃-TPMM behaves as a facial ligand. Both the ligands were functionalized with terminal thiol for immobilization on gold nanoparticles (AuNPs), and the corresponding iron(II) complexes [(6Me₂-BPASH)Fe(BF)(ClO₄)]@C₈Au (2a) and [(6Me₃-TPMSH)Fe(BF)(ClO₄)]@C₈Au (2b) were prepared to probe the effect of immobilization on their ability to perform bioinspired oxidation reactions. All the complexes react with dioxygen to display the oxidative decarboxylation of the coordinated benzoylformate, but the complexes supported by 6Me₃-TPMM and its thiol-appended ligand display faster reactivity compared to their analogues with the 6Me₂-Me-BPA-derived ligands. In each case, an electrophilic iron-oxygen oxidant was intercepted as the active oxidant generated from dioxygen. The immobilized complexes (2a and 2b) display enhanced O₂-dependent reactivity in oxygen-atom transfer reactions (OAT) and hydrogen-atom transfer (HAT) reactions compared to their homogeneous congeners (1a and 1b). Furthermore, the immobilized complex 2b displays catalytic OAT reactions. This study supports that the ligand geometry and immobilization on AuNPs influence the dioxygen-dependent reactivity of the complexes.

Gold Nanomaterials and their Composites as Electrochemical Sensing Platforms for Nitrite Detection

Nitrite is one of the abundant toxic components existing in the environment and is likely to have a great potential to affect human health badly. For that reason, it has become crucial to build a reliable nitrite detection method. In recent years, several nitrite monitoring systems have been proposed. Compared with traditional analytical strategies, the electrochemical approach has a bunch of advantages, including low cost, rapid response, easy operation, simplicity, etc. In this case, noble metal nanomaterials, especially Au-based nanomaterials, have attracted attention in electrode modification because of higher catalytic activity, facile mass transfer, and broad active area for determining nitrite. This review is based on the state-of-the-art, which includes a variety of nanomaterials that have been coupled with AuNPs for the creation of nanocomposites, and the construction as well as development of electrochemical sensors for nitrite detection over the last few years (2016-2022). A background study on synthesizing different morphological AuNPs and nanocomposites has also been introduced. The fabrication methods and sensing capabilities of modified electrodes are given special consideration.

Synthesis and Organization of Gold-Peptide Nanoparticles for Catalytic Activities

A significant development in the synthesis strategies of metal-peptide composites and their applications in biomedical and bio-catalysis has been reported. However, the random aggregation of gold nanoparticles provides the opportunity to find alternative fabrication strategies of gold-peptide composite nanomaterials. In this study, we used a facile strategy to synthesize the gold nanoparticles via a green and simple approach where they show self-alignment on the assembled nanofibers of ultrashort oligopeptides as a composite material. A photochemical reduction method is used, which does not require any external chemical reagents for the reduction of gold ions, and resultantly makes the gold nanoparticles of size ca. 5 nm under mild UV light exposure. The specific arrangement of gold nanoparticles on the peptide nanofibers may indicate the electrostatic interactions of two components and the interactions with the amino group of the peptide building block. Furthermore, the gold-peptide nanoparticle composites show the ability as a catalyst to degradation of environmental pollutant p-nitrophenol to p-aminophenol, and the reaction rate constant for catalysis is calculated as 0.057 min-1 at a 50-fold dilute sample of 2 mg/mL and 0.72 mM gold concentration in the composites. This colloidal strategy would help researchers to fabricate the metalized bioorganic composites for various biomedical and bio-catalysis applications.

Interfacial Synthesis: Morphology, Structure, and Properties of Interfacial Formations in Liquid–Liquid Systems

Abstract

The results of studies in the field of interfacial synthesis and interfacial formations in liquid–liquid systems are summarized. The mechanisms of the processes of interfacial synthesis are considered. Data on the self-assembly of nanoparticles, films, and 3D materials are given. The properties of materials of interfacial formations in systems with rare-earth elements and di(2-ethylhexyl)phosphoric acid, obtained both in the presence and absence of local vibrations, are described. It was established that materials obtained in the presence of local vibrations in the interfacial layer have higher density, melting point, and magnetic susceptibility and lower electric conductivity. The effect of force field parameters on the properties of interfacial formations is considered. Practical applications and prospects for research in the field of interfacial formations are discussed.

When organophosphorus ruthenium complexes covalently bind to ruthenium nanoparticles to form nanoscale hybrid materials

A hybrid material made of mononuclear organophosphorus polypyridyl ruthenium complexes covalently bonded to ruthenium nanoparticles has been synthesized via a one-pot organometallic procedure and finely characterized. These results open new avenues to access unique hybrid transition metal nanomaterials.

Gold nanomaterials as key suppliers in biological and chemical sensing, catalysis, and medicine

BACKGROUND

Gold nanoparticles (AuNPs) with unique physicochemical properties have received a great deal of interest in the field of biological, chemical and biomedical implementations. Despite the widespread use of AuNPs in chemical and biological sensing, catalysis, imaging and diagnosis, and more recently in therapy, no comprehensive summary has been provided to explain how AuNPs could aid in developing improved sensing and catalysts systems as well as medical settings.

SCOPE OF REVIEW

The chemistry of Au-based nanosystems was followed by reviewing different applications of Au nanomaterials in biological and chemical sensing, catalysis, imaging and diagnosis by a number of approaches, and finally synergistic combination therapy of different cancers. Afterwards, the clinical impacts of AuNPs, future application of AuNPs, and opportunities and challenges of AuNPs application were also discussed.

MAJOR CONCLUSIONS

AuNPs show exclusive colloidal stability and are considered as ideal candidates for colorimetric detection, catalysis, imaging, and photothermal transducers, because their physicochemical properties can be tuned by adjusting their structural dimensions achieved by the different manufacturing methods.

GENERAL SIGNIFICANCE

This review provides some details about using AuNPs in sensing and catalysis applications as well as promising theranostic nanoplatforms for cancer imaging and diagnosis, and sensitive, non-invasive, and synergistic methods for cancer treatment in an almost comprehensive manner.

Spectroscopic Evidence for Ligand Substitution Reactions at the Solid-Liquid Interface of a Sub-micrometer Gold(I) Carbene Complex

Colloidal coordination compounds in the sub-micrometer range were synthesized from a chloro gold(I) carbene complex via the anti-solvent procedure and stabilized by a surfactant shell of Tween 20. This compound was successfully applied as model system to monitor heterogeneous multiphase ligand substitution reactions at the solid-liquid interface.

Electrochemical Behavior and Electrodeposition of Nanostructured Rhodium from Low-Temperature Carbamide and Acetamide Containing Melts

The electrochemical behavior of rhodium at low-temperature carbamide-chloride and acetamide-chloride melts was investigated. It was found that, during rhodium anodic dissolution in carbamide and acetamide containing chloride melts, mixed complexes [Rh(NH₃)₄Cl₂]⁺ of quasi-octahedral symmetry D_4h are produced. The composition and structure of nascent complex ions have been studied. During electrochemical reduction of [Rh(NH₃)₄Cl₂]⁺ complexes, the synthesis of Rh nanoparticles, as well as Fe, Cu, and Mo nanocoatings, were realized.

Porphyrin metal complex monolayer-protected gold nanorods: a parallel facile synthesis and self-assembly

Porphyrin metal (Zn, Cu, and Mg) complex monolayer-protected gold nanorods (GNRs) were, for the first time, synthesized. Their synthesis was easy to access by mixing porphyrin encapsulated GNRs with corresponding excess soluble metal salts in solution, followed by the facile purification through centrifugation and sonication due to the gravity of the GNRs and their solubility in organic solvents. Furthermore, the resulting three GNRs exhibited distinct spectroscopic properties and were able to self-assemble into side-by-side arrays driven by π-π intermolecular interactions of the surface metal porphyrin chromophores.