Redox reactions of a pyrazine-bridged RuIII(edta) binuclear complex: spectrochemical, spectroelectrochemical and theoretical studies.

The redox reactions of a pyrazine-bridged binuclear [(edta)RuIIIpzRuIII(edta)]2- (edta4- = ethylenediaminetetraacetate; pz = pyrazine) have been investigated spectrochemically and spectroelectrochemically for the first time. The kinetics of the reduction of [(edta)RuIIIpzRuIII(edta)]2- (RuIII-RuIII) with the ascorbic acid anion (HA-) was studied as a function of ascorbic concentration and temperature at a fixed pH 6.0. The overall reaction of RuIII-RuIII was found to consist of two-steps involving the initial formation of the mixed-valence [(edta)RuIIpzRuIII(edta)]3- (RuII-RuIII) intermediate complex (λmax = 462 nm, εmax = 10 000 M-1 cm-1), which undergoes further reduction by ascorbic acid to produce the [(edta)RuIIpzRuII(edta)]4-(RuII-RuII) ultimate product complex (λmax = 540 nm, εmax = 20 700 M-1 cm-1). Our studies further revealed that the RuII-RuIII and RuII-RuII species are formed in the electrochemical reduction of the RuIII-RuIII complex at 0.0 and -0.4 V (vs. SHE), respectively. Formation of RuII-RuIII and RuII-RuII was further corroborated by magnetic moment measurements and DFT calculations. Kinetic data and activation parameters are interpreted in terms of a mechanism involving rate-determining outer-sphere electron transfer between Ru(III) and the ascorbate monoanion (HA-) at pH 6.0. A detailed reaction mechanism in agreement with the spectral, spectro-electrochemical and kinetic data is presented. The results of the spectral and kinetic studies of the reaction of the RuII-RuII complex with molecular oxygen (O2) reveal the ability of the RuII-RuII species to effect the oxygen reduction reaction (ORR) leading to the formation of H2O2, a partial reduction product of dioxygen (O2).

Antibactericidal Ir(III) and Ru(II) Complexes with Phosphine-Alkaloid Conjugate and Their Interactions with Biomolecules: A Case of N-Methylphenethylamine.

The phosphine ligand (Ph2 PCH2 N(CH3 )(CH2 )2 Ph, PNMPEA) obtained by the reaction of the (hydroxymethyl)diphenylphosphine with naturally occurring alkaloid N-methylphenethylamine, was used to synthesize the half-sandwich iridium(III) (Ir(η5 -Cp*)Cl2 Ph2 PCH2 N(CH3 )(CH2 )2 Ph, IrPNMPEA) and ruthenium(II) (Ru(η6 -p-cymene)Cl2 Ph2 PCH2 N(CH3 )(CH2 )2 Ph, RuPNMPEA) complexes. They were characterized using a vast array of methods, including 1D and 2D NMR, ESI(+)MS spectrometry, elemental analysis, cyclic voltammetry (CV), electron spectroscopy in the UV-Vis range (absorption, fluorescence) and density functional theory (DFT). The initial antimicrobial activity in vitro toward Gram-positive and Gram-negative bacterial strains was examined, indicating that both complexes are selective towards Gram-positive bacteria, e. g., Staphylococcus aureus, where the IrPNMPEA has been more bactericidal compared to RuPNMPEA. Additionally, the interactions of these compounds with various biomolecules, such as DNA (ctDNA, plasmid DNA, 9-ethylguanine (9-EtG), and 9-methyladenine (9-MeA)), nicotinamide adenine dinucleotide (NADH), glutathione (GSH), and ascorbic acid (Asc) were described. The results showed that both Ir(III) and Ru(II) complexes accelerate the oxidation process of NADH, GSH and Asc that appeared to occur by an electron transfer mechanism. Interestingly, only IrPNMPEA leads to the formation of various biomolecule adducts, which can explain its higher activity. Furthermore, RuPNMPEA and IrPNMPEA have been interacting with the DNA through weak noncovalent interactions.

Liposomal Binuclear Ir(III)-Cu(II) Coordination Compounds with Phosphino-Fluoroquinolone Conjugates for Human Prostate Carcinoma Treatment.

Novel heteronuclear IrIII-CuII coordination compounds ([Ir(η5-Cp*)Cl2Pcfx-Cu(phen)](NO3)·1.75(CH3OH)·0.75(H2O) (1), [Ir(η5-Cp*)Cl2Pnfx-Cu(phen)](NO3)·1.75(CH3OH)·0.75(H2O) (2), [Ir(η5-Cp*)Cl2Plfx-Cu(phen)](NO3)·1.3(H2O)·1.95(CH3OH) (3), [Ir(η5-Cp*)Cl2Psfx-Cu(phen)] (4)) bearing phosphines derived from fluoroquinolones, namely, sparfloxacin (Hsfx), ciprofloxacin (Hcfx), lomefloxacin (Hlfx), and norfloxacin (Hnfx), have been synthesized and studied as possible anticancer chemotherapeutics. All compounds have been characterized by electrospray ionization mass spectrometry (ESI-MS), a number of spectroscopic methods (i.e., IR, fluorescence, and electron paramagnetic resonance (EPR)), cyclic voltammetry, variable-temperature magnetic susceptibility measurements, and X-ray diffractometry. The coordination geometry of IrIII in all complexes adopts a characteristic piano-stool geometry with the η5-coordinated and three additional sites occupied by two chloride and phosphine ligands, while CuII ions in complexes 1 and 2 form a distorted square-pyramidal coordination geometry, and in complex 3, the coordination geometry around CuII ions is a distorted octahedron. Interestingly, the crystal structure of [Ir(η5-Cp*)Cl2Plfx-Cu(phen)] features the one-dimensional (1D) metal-organic polymer. Liposomes loaded with redox-active and fluorescent [Ir(η5-Cp*)Cl2Pcfx-Cu(phen)] (1L) have been prepared to increase water solubility and minimize serious systemic side effects. It has been proven, by confocal microscopy and an inductively coupled plasma mass spectrometry (ICP-MS) analysis, that the liposomal form of compound 1 can be effectively accumulated inside human lung adenocarcinoma and human prostate carcinoma cells with selective localization in nuclei. A cytometric analysis showed dominance of apoptosis over the other cell death types. Furthermore, the investigated nanoformulations induced changes in the cell cycle, leading to S phase arrest in a dose-dependent manner. Importantly, in vitro anticancer action on three-dimensional (3D) multicellular tumor spheroids has been demonstrated.

Indium-modified copper nanocubes for syngas production by aqueous CO2 electroreduction.

Electroreduction of carbon dioxide represents an appealing strategy to rethink a waste product as a valuable feedstock for the formation of value-added compounds. Among the metal electrodes able to catalyze such processes, copper plays a central role due to its rich chemistry. Strategies aimed at tuning Cu selectivity comprise nanostructuring and alloying/post-functionalization with heterometals. In this contribution, we report on straightforward electrochemical methods for the formation of nanostructured Cu-In interfaces. The latter were fully characterized and then used as cathodes for CO2 electroreduction in aqueous environment, leading to the selective production of syngas, whose composition varies upon changing the applied bias and indium content. In particular, gaseous mixtures compatible with the synthesis of methanol or aldehydes (i.e. respectively with 1 : 2 and 1 : 1 CO/H2 ratios) are produced at low (i.e. -0.62 V vs. RHE) applied bias with >3.5 mA cm-2 current densities (in absolute value). Even if the proposed cathodes undergo structural modifications upon prolonged exposure to CO2 reduction conditions, their catalytic activity can be restored by introducing an additional In(III) precursor to the electrolytic solution.

Two out of Three Musketeers Fight against Cancer: Synthesis, Physicochemical, and Biological Properties of Phosphino CuI, RuII, IrIII Complexes.

Two novel phosphine ligands, Ph2PCH2N(CH2CH3)3 (1) and Ph2PCH2N(CH2CH2CH2CH3)2 (2), and six new metal (Cu(I), Ir(III) and Ru(II)) complexes with those ligands: iridium(III) complexes: Ir(η5-Cp*)Cl2(1) (1a), Ir(η5-Cp*)Cl2(2) (2a) (Cp*: Pentamethylcyclopentadienyl); ruthenium(II) complexes: Ru(η6-p-cymene)Cl2(1) (1b), Ru(η6-p-cymene)Cl2(2) (2b) and copper(I) complexes: [Cu(CH3CN)2(1)BF4] (1c), [Cu(CH3CN)2(2)BF4] (2c) were synthesized and characterized using elemental analysis, NMR spectroscopy, and ESI-MS spectrometry. Copper(I) complexes turned out to be highly unstable in the presence of atmospheric oxygen in contrast to ruthenium(II) and iridium(III) complexes. The studied Ru(II) and Ir(III) complexes exhibited promising cytotoxicity towards cancer cells in vitro with IC50 values significantly lower than that of the reference drug-cisplatin. Confocal microscopy analysis showed that Ru(II) and Ir(III) complexes effectively accumulate inside A549 cells with localization in cytoplasm and nuclei. A precise cytometric analysis provided clear evidence for the predominance of apoptosis in induced cell death. Furthermore, the complexes presumably induce the changes in the cell cycle leading to G2/M phase arrest in a dose-dependent manner. Gel electrophoresis experiments revealed that Ru(II) and Ir(III) inorganic compounds showed their unusual low genotoxicity towards plasmid DNA. Additionally, metal complexes were able to generate reactive oxygen species as a result of redox processes, proved by gel electrophoresis and cyclic voltamperometry. In vitro cytotoxicity assays were also carried out within multicellular tumor spheroids and efficient anticancer action on these 3D assemblies was demonstrated. It was proven that the hydrocarbon chain elongation of the phosphine ligand coordinated to the metal ions does not influence the cytotoxic effect of resulting complexes in contrast to metal ions type.

Syngas Evolution from CO2 Electroreduction by Porous Au Nanostructures.

Electrocatalytic reduction of CO2 recently emerged as a viable solution in view of changing the common belief and considering carbon dioxide as a valuable reactant instead of a waste product. In this view, we herein propose the one-step synthesis of gold nanostructures of different morphologies grown on fluorine-doped tin oxide electrodes by means of pulsed-laser deposition. The resulting cathodes are able to produce syngas mixtures of different compositions at overpotentials as low as 0.31 V in CO2-presaturated aqueous media. Insights into the correlation between the structural features/morphology of the cathodes and their catalytic activity are also provided, confirming recent reports on the remarkable sensitivity toward CO production for gold electrodes exposing undercoordinated sites and facets.