Inorganics

The article discusses the interaction in amino acid–gold cyanide systems using amino acids of different structures. The formation of complex compounds of gold cyanide with amino acids with the participation of carboxyl and amino groups is shown. A relationship has been established between the formation of gold complexes with amino acids and the degree of its extraction in the process of leaching from low-grade ore with sodium cyanide together with amino acids: the higher the degree of participation of the amino group in the formation of the complex, i.e., covalent bond, the more pronounced the effect of the amino acid on the degree of gold leaching. The contribution to the formation of the complex of the carboxyl group (ionic bond) and the amino group (covalent donor–acceptor) can be assessed by the intensity of the band at a wave number of 1419 cm⁻¹ of the IR spectra of the systems: gold cyanide–amino acid. This approach makes it possible to predict the effect of amino acid structure on gold recovery during cyanide leaching based on IR spectra. Full article

Ruthenium(II/III)-based compounds have gained significant interest due to the biocompatibility of ruthenium, its similarity to iron, and the possibility for structural diversification through the choice of ligands. In this contribution, two novel ligands, (2-(2-methoxyethoxy)ethyl nicotinate hydrochloride) and (2-[2-(2-methoxyethoxy)ethoxy]ethyl nicotinate hydrochloride) (pyCOO(CH₂CH₂O)_nCH₃: L2, n = 2; L3, n = 3), were synthesized and characterized via ESI-HRMS, as well as IR and NMR spectroscopies. Their structures were optimized at the B3LYP/6-311++G(d,p) level of theory, and NMR chemical shifts were predicted, along with the most important intramolecular interactions. Additionally, two neutral complexes of the general formula [RuCl₂(η⁶-p-cym) (L-κN)] (L = L2: 2; L3: 3) and two cationic complexes of the general formula [RuCl(η⁶-p-cym)(L-κN)₂][PF₆] (L = L1: 4; L2: 5) were obtained and characterized. The optimization of the structures was performed at the B3LYP/6-31+G(d,p)(H,C,N,O,Cl)/LanL2DZ(Ru) level of theory. Structural features were described, and intramolecular stabilization interactions were outlined. Full article

In this work, the combined effects of anion substitution (with Br⁻ and I⁻) and SiO₂ addition on the Li-ion conductivity in LiBH₄ have been investigated. Hexagonal solid solutions with different compositions, h-Li(BH₄)_1−α(X)_α (X = Br, I), were prepared by ball milling and fully characterized. The most conductive composition for each system was then mixed with different amounts of SiO₂ nanoparticles. If the amount of added complex hydride fully fills the original pore volume of the added silica, in both LiBH₄-LiBr/SiO₂ and LiBH₄-LiI/SiO₂ systems, the Li-ion conductivity was further increased compared to the h-Li(BH₄)_1−α(X)_α solid solutions alone. The use of LiBH₄-LiX instead of LiBH₄ in composites with SiO₂ enabled the development of an optimal conductive pathway for the Li ions, since the h-Li(BH₄)_1−α(X)_α possesses a higher conductivity than LiBH₄. In fact, the Li conductivity of the silica containing h-Li(BH₄)_1−α(X)_α is higher than the maximum reached in LiBH₄-SiO₂ alone. Therefore, a synergetic effect of combining halogenation and interface engineering is demonstrated in this work. Full article

Two-dimensional (2D) nanolayered and nanohybrid structures, which are composed of different species of organic anions and multi-valence inorganic cations, are considered favorable in the field of energy storage for use as supercapacitors. In this study, host–guest interactions were used to build a series of these nanohybrids. The host was the layered double hydroxides of vanadium–cobalt (V/Co) nanolayers with different molar ratios. Cyanate was used as a guest to design a V/Co supercapacitor with a 2D-nanolayered structure. In addition, oxalate was used as a new additive to improve the performance of the V/Co supercapacitor. X-ray diffraction, infrared spectroscopy, thermal analyses, and scanning electron microscopy confirmed the formation of the nanolayered structures of cyanate-V/Co. In the case of the oxalate-V/Co nanostructures, a new phase of cobalt oxalate was produced and combined with the nanolayered structure to build a 3D porous structure. A three-assembly electrode system was used to study the electrochemical supercapacitive behavior of the cyanate-V/Co and oxalate-V/Co nanolayered structures. The results indicated that the OXVC-20 electrode possessed the highest specific capacitance as compared to that of the OXVC-16 and CNOVC electrodes. An excellent stability performance of up to 91% after various charge–discharge cycles was detected for the optimum case. Because of the positive effect of oxalate on the supercapacitance performance of the V/Co supercapacitor, it is suggested as a new track for building active electrodes for high-performance supercapacitor applications. Full article

The reaction of UO₂ with the respective lanthanide metal and purified graphite in an arc-melting furnace led to the formation of solid solutions of the composition Ln_xU_1−xC₂, with Ln = Tb, Dy, Ho, Tm, and Lu. They all crystallize in the tetragonal CaC₂ type structure (I4/mmm, Z = 2). Elemental analyses of selected samples (EDX) confirm that the composition of the resulting solid solution is in reasonable agreement with the nominal (weighed-in) composition of the starting materials, i.e., a significant evaporation of the lanthanide metals during the arc-melting synthesis does not occur. The lattice parameters of the solid solutions were extracted using Le Bail fits of high-resolution synchrotron powder diffraction data (beamline P02.1, DESY, Hamburg, Germany; beamline BL 09, DELTA, Dortmund, Germany), revealing ideal Vegard behavior for all five solid solutions. XANES investigations on all compounds at the Ln-L_III and U-L_III edges reveal that the occupancies of the U-6d orbitals decrease with increasing x, whereas the occupancies of the Ln-5d orbitals increase, pointing to an electron transfer from the uranium to the lanthanide cations. Examination of the shifts of the absorption edge (E₀) leads to the same finding. Full article

This contribution describes the preparation, coupled with detailed characterization, of Nb₂O₅ nanofibers and their application in lithium–sulfur batteries for the improvement of electrochemical performance. The utilization of reactive needle-less electrospinning allowed us to obtain, in a single step, amorphous pre-ceramic composite PAN/Nb₂O₅ fibers, which were transformed into porous ceramic Nb₂O₅ nanofibers via calcination. Thermogravimetric studies defined that calcination at 600 °C results in crystalline ceramic fibers without carbon residues. The fibrous morphology and mean diameter (614 ± 100 nm) of the ceramic nanofibers were analyzed via scanning and transmission electron microscopy. A surface area of 7.472 m²/g was determined through nitrogen adsorption measurements, while a combination of X-ray diffraction and Raman spectroscopy was used to show the crystallinity and composition of the fibers after calcination—single T-phase Nb₂O₅. Its performance in the cathode of lithium–sulfur batteries was defined through electrochemical tests, and the obtained results were compared to a similar blank electrode. The initial discharge capacity of 0.5 C reached a value of 570 mAh∙g⁻¹, while the reversible capacity of 406 mAh∙g⁻¹ was retained after 200 cycles, representing a capacity retention of 71.3%. The presence of Nb₂O₅ nanofibers in the carbon cathode inhibits the shuttle effect through polysulphide confinement, which originates from porosity and chemical trapping. Full article

A rapid synthesis method is used to form multivariate metal–organic frameworks (MTV-MOFs) with the UiO-66 structure, where precipitation occurs upon mixing solutions of ligands and metal salts at temperatures less than 60 °C. The materials include mixtures of metals and ligands, Ce/Zr-UiO-66(1,4-NDC/BDC), Ce/Zr-UiO-66(1,4-NDC/2,6-NDC), Ce/Zr-UiO-66(1,4-NDC), Ce/Ti-UiO-66(1,4-NDC), and Ce/Ti-UiO-66(BDC-NH₂) (NDC = naphthalene dicarboxylate, BDC = benzene-1,4-dicarboxylate, BDC-NH₂ = 2-amino-benzene-1,4-dicarboxylate). Phase purity was determined by powder X-ray diffraction (PXRD), with a broadening of the profile indicative of nanoscale crystallites, verified by scanning electron microscopy (SEM). The molar ratio of metals and organic ligands in Ce/Zr-UiO-66(1,4-NDC/2,6-NDC) was confirmed by X-ray fluorescence (XRF) and solution ¹H nuclear magnetic resonance (NMR) after digestion, respectively. Analysis of the adsorption of dyes by the MTV-MOFs showed that a pseudo-first-order model accounts for the kinetics. The effectiveness of photocatalytic degradation of two cationic (methylene blue and rhodamine B) and two anionic (Congo red and Alizarin Red S (AR)) dyes was studied under UV and visible light. The most effective photocatalytic degradation was found between 1 and 15 min towards both cationic and anionic dyes by Ce/Zr-UiO-66(1,4-NDC/2,6-NDC). Measurements of recyclability and photostability showed retention of crystallinity after five cycles of use and exposure to light for 17 h, as confirmed by PXRD. Full article

This study explores the potential for repairing small, isolated delamination areas in carbon fiber-reinforced polymer (CFRP), while preserving the integrity of the composite structures. A small drilled hole at the center of the delamination section served as a channel for the epoxy infill of the sharp delamination cracks. The pressureless infill repair was achieved through the capillary action of an acetone-diluted resin pre-coating (RPC) solution (without hardener) with CNT reinforcement, comprising 89 m/m% acetone, 10 m/m% resin, and 1 m/m% CNT. This acetone-rich resin pre-coating (RPC) solution is easily prepared and applied to the drilled hole area. Curing of the CNT-toughened resin infill was induced by filling the small drilled hole with a resin–hardener mixture toughened by CNT/aramid pulp. The effectiveness of the delamination repair was compared for curing periods of two weeks and three months. The flexural strength measurements indicated that a restoration level of 77% was achieved in this study, while the optimum 100% restoration was achieved using the same technique for edge delamination repairs. Full article

Indigo carmine dye falls into the category of toxic chemicals, potentially leading to irritation and allergic reactions in certain individuals. Thus, this study employed the Pechini sol–gel strategy to easily produce CoFe₂O₄ nanoparticles, which serve as an effective adsorbent for the disposal of indigo carmine dye from aqueous solutions. The maximum adsorption capacity of CoFe₂O₄ for indigo carmine dye was determined to be 421.94 mg/g. The synthesized CoFe₂O₄ nanoparticles exhibited an average crystallite size of 18.75 nm. SEM analysis revealed that these nanoparticles were nearly spherical, with an average grain size of 198.32 nm. Additionally, TEM analysis indicated a fully agglomerated spherical morphology for the CoFe₂O₄ sample, with an average diameter of 15.37 nm. The EDS spectrum confirmed that the synthesized CoFe₂O₄ nanoparticles consisted of Co, Fe, and O elements, with respective weight percentages of 17.82%, 49.46%, and 32.72%. The removal of indigo carmine dye by the synthesized CoFe₂O₄ is spontaneous, chemical, exothermic, closely fitting the pseudo-second-order kinetic model, and demonstrating a strong concordance with the Langmuir equilibrium isotherm. Full article

Functional dependence of the axial zero-field splitting parameter D with respect to a properly chosen geometrical parameter (D_str) in metal complexes is termed the magnetostructural D-correlation. In mononuclear hexacoordinate Ni(II) complexes with the ground electronic term ³B_1g (³A_2g in the regular octahedron), it proceeds along two intercepting straight lines, allowing for predicting the sign and magnitude of the D-parameter by knowing the X-ray structure alone; D_str is constructed from the metal–ligand bond lengths. In hexacoordinate Co(II) complexes, it is applicable only in the segment of the compressed bipyramid where the ground electronic term ⁴B_1g is orbitally non-degenerate so that the spin Hamiltonian formalism holds true. The D vs. D_str correlation is strongly non-linear, and it is represented by a set of decreasing exponentials. In tetracoordinate Co(II) complexes, on the contrary, the angular distortion from the regular tetrahedron is crucial so that the appropriate structural parameter D_str is constructed of bond angles. The most complex case is represented by pentacoordinated Co(II) systems, for which it is not yet possible to define a statistically significant correlation. All of these empirical correlations originate in the electronic structure of metal complexes that can be modelled using generalized crystal-field theory. As the barrier to spin reversal in single-molecule magnets is proportional to the D-value, for rational tuning and/or prediction of the single-molecule magnetic behaviour, knowledge/prediction of the D-parameter is beneficial. In this review, we present the statistical processing of an extensive set of structural and magnetic data on Co(II) and Ni(II) complexes, which were published over the past 15 years. Magnetostructural D-correlations defined for this data set are reviewed in detail. Full article

Treatment regimens are regularly evolving alongside novel therapies and drugs. Such evolution is necessary to circumvent resistance mechanisms and to give patients the best possible health care. When dealing with cancer, most regimens involve multiple treatments (surgery, radiation therapy, chemotherapy, immunotherapy, etc.). The purpose of this study was to associate in a single compound metal-based drugs and photosensitizers to combine chemotherapy and photodynamic therapy. Two arene–ruthenium tetrapyridylporphyrin compounds (2H-TPyP-arene-Ru and Zn-TPyP-arene-Ru) have been synthesized and evaluated on two colorectal cancer cell lines (HCT116 and HT-29). Their cytotoxicity and phototoxicity have been evaluated. In addition, the anticancer mechanism and the cell death process mediated by the two compounds were studied. The results showed that the two arene–ruthenium photosensitizer-containing complexes have a strong phototoxic effect after photoactivation. The 2H-TPyP-arene-Ru complex induced outstanding cytotoxicity when compared to the Zn-TPyP-arene-Ru analogue. Moreover, under light, these two arene–ruthenium photosensitizers induce an apoptotic process in human colorectal cancer cell lines. Full article

The Escherichia coli fumarate and nitrate reduction (FNR) regulator acts as the cell’s master switch for the transition between anaerobic and aerobic respiration, controlling the expression of >300 genes in response to O₂ availability. Oxygen is perceived through a reaction with FNR’s [4Fe-4S] cluster cofactor. In addition to its primary O₂ signal, the FNR [4Fe-4S] cluster also reacts with nitric oxide (NO). In response to physiological concentrations of NO, FNR de-represses the transcription of hmp, which encodes a principal NO-detoxifying enzyme, and fails to activate the expression of the nitrate reductase (nar) operon, a significant source of endogenous cellular NO. Here, we show that the L28H variant of FNR, which is much less reactive towards O₂ than wild-type FNR, remains highly reactive towards NO. A high resolution structure and molecular dynamics (MD) simulations of the closely related L28H-FNR from Aliivibrio fischeri revealed decreased conformational flexibility of the Cys20-Cys29 cluster-binding loop that is suggested to inhibit outer-sphere O₂ reactivity, but only partially impair inner-sphere NO reactivity. Our data provide new insights into the mechanistic basis for how iron–sulfur cluster regulators can distinguish between O₂ and NO. Full article

(1) Background: The compound ytterbium trifluoride is used as a component of several dental materials, and this is reviewed in the current article. (2) Methods: Published articles on this substance were identified initially from PubMed, and then from Science Direct and Google Scholar. The publications identified in this way showed that ytterbium trifluoride has been included in a variety of dental restorative materials, including composite resins, glass polyalkenoate cements, and calcium trisilicate cements. (3) Results: Ytterbium trifluoride is reported to be insoluble in water. Despite this, its presence is associated with fluoride release from dental materials. There is evidence that it reacts with the components of calcium trisilicate cements to form small amounts of a variety of compounds, including ytterbium oxide, Yb₂O₃, and calcium–ytterbium fluoride, CaYbF₅. In nanoparticulate form, it has been shown to reinforce glass polyalkenoates and it also provides high contrast in X-ray images. (4) Conclusions: Ytterbium trifluoride is a useful component of dental materials, though some of the published findings suggest that there are aspects of its chemistry which are poorly understood. Full article

Valence tautomerism (VT) may occur if a molecule contains two chemically different redox-active units, which differ only slightly in their intrinsic redox potential. Herein, we present three new half-sandwich complexes [(η⁶-arene)Cr(CO)₂L]⁺ with a triarylmethylium substituent appended to the π-coordinated arene and different coligands L (L = CO, P(OPh)₃, PPh₃, 1⁺–3⁺) at the chromium atom. Ligand substitution purposefully lowers the half-wave potential for chromium oxidation and thereby the redox potential difference towards tritylium reduction. For the PPh₃-substituted complex 3⁺, cyclic voltammetry measurements indicate that chromium oxidation and tritylium reduction occur at (almost) the same potential. This renders the diamagnetic Cr(0)-C₆H₄-CAr₂⁺ form 3⁺, and its paramagnetic diradical Cr(I)^+•-C₆H₄-CAr₂^• valence tautomer 3^+•• energetically nearly degenerate. Temperature-dependent IR spectroscopy indeed shows two pairs of carbonyl bands that are assignable to a Cr(0) and a Cr(I) species, coexisting in a T-dependent equilibrium with almost equal quantities for both at −70 °C. The diradical form with one unpaired spin at the trityl unit engages in a monomer ⇌ dimer equilibrium, which was investigated by means of quantitative EPR spectroscopy. The diradical species 1^+••–3^+•• were found to be highly reactive, leading to several identified reaction products, which presumably result from hydrogen atom abstraction via the trityl C atom, e.g., from the solvent. Full article

The use of ionic liquid [emim][Tf₂N] as an additive in polyethersulphone (PES) and nano-sized silico-aluminophosphate-34 (SAPO-34) mixed matrix membrane was studied through the incorporation of different amounts of [emim][Tf₂N] in the membrane composition, as presented in this work, varying from 10 to 40 wt%. Through gas permeation tests using CO₂ and N₂, the membrane composition containing 20 wt% [emim][Tf₂N] led to the highest increase in CO₂ permeability and CO₂/N₂ selectivity. The use of low concentrations of additive (10–20 wt%) promoted a state called antiplasticization; in this state, the permeability was even more regulated by the kinetic diameter of the species which, in this work, permitted achieving a higher CO₂/N₂ selectivity while increasing the CO₂ permeability until an optimal condition. [emim][Tf₂N] also promoted a better dispersion of SAPO-34 particles and an increase in the flexibility of the polymeric matrix when compared to a film with the same composition without [emim][Tf₂N]. Moreover, the characterizations corroborated that the inclusion of [emim][Tf₂N] increased the zeolite dispersion and improved the polymer/zeolite compatibility and membrane flexibility, characterized by a decrease in glass transition temperature, which helped in the fabrication process while presenting a similar thermal resistance and hydrophilicity as neat PES membrane, without affecting the membrane structure, as indicated by FTIR and a contact angle analysis. Full article

Two new ligands were synthesized with the goal of copper stabilization, N,N′-(2-methylpyridine)-2,11-diaza[3,3](2,6)pyridinophane (^PicN4) and N-(methyl),N′-(2-methylpyridine)-2,11-diaza[3,3](2,6)pyridinophane (^PicMeN4), by selective functionalization of ^HN4 and ^TsHN4. These two ligands, when reacted with various copper salts, generated both Cu(II) and Cu(I) complexes. These ligands and Cu complexes were characterized by various methods, such as NMR, UV-Vis, MS, and EA. Each compound was also examined electrochemically, and each revealed reversible Cu(II)/Cu(I) redox couples. Additionally, stability constants were determined via spectrophotometric titrations, and radiolabeling and cytotoxicity experiments were performed to assess the chelators relevance to their potential use in vivo as ⁶⁴Cu PET imaging agents. Full article

Two ternary copper(II) complexes with an anthraquinone and a N,N-heterocyclic donor, [Cu(dmp)(L)(H₂O)](ClO₄) (1), [Cu(bpy)(L)(dmso)](ClO₄) (2), in which dmp = 2,9-dimethyl-1,10-phenanthroline, bpy = 2,2′-bipyridine, and HL = 1-hydroxyanthracene-9,10-dione were synthesized and fully characterized by conductivity, elemental, and spectral analyses (FTIR and UV-Vis; EPR and ESI-MS). The structure of 1 reveals that Cu(II) is bound to two oxygens of L, two nitrogens of dmp, and a molecule of water in the fifth position. In complex 2.1, Cu(II) is also pentacoordinated with an O-bonded dmso in the axial position. The presence of the heteroleptic complexes in solution was evidenced by ESI-MS, EPR in dmso solution and UV-Vis spectrophotometry. All complexes bind to CT-DNA with affinity constants of approximately 10⁴. Complex 2 can nick plasmid DNA but no cleavage was performed by complex 1. The investigation of DNA interactions by spectrofluorimetry using ethidium bromide (EB) showed that it was displaced from DNA sites by the addition of the complexes. The complexes inhibited the growth of chronic myelogenous leukemia and human squamous carcinoma cells with low IC₅₀ values, complex 1 being the most effective. Full article

By employing semi-flexible multi-N donor auxiliary ligands, namely 1,4-bis(5-pyrimidyl)benzene (bpmb) in conjunction with azide, novel Co(II) 2D coordination polymers have been successfully synthesized and structurally characterized, along with magnetic analysis. The resulting compound, {Co(N₃)(bpmb)(H₂O)₂·H₂O}_n (1), exhibits a unique 2D structure comprised of interconnected Co(II) chains bridged by single end-to-end (EE) azide moieties. These chains are further linked by twisted trans-μ₂-N,N′-bpmb auxiliary ligands, forming a grid-like network. Additionally, the layers are held together in a 3D arrangement through hydrogen bonding interactions between the coordination water and the N atom of the bpmb ligands. Importantly, magnetic investigations reveal that compound 1 displays weak ferromagnetism attributed to spin canting, with a critical temperature (Tc) of 12 K. Full article

Lycorine (LYC) is an active alkaloid first isolated from Narcissus pseudonarcissus and found in most Amaryllidaceae plants. It belongs to the same family as galantamine, which is the active component of a drug used for the treatment of Alzheimer’s disease. Similarly to galantamine, LYC is able to suppress induced amyloid β (Aβ) toxicity in differentiated SH-SY5Y cell lines and it can weakly interact with the N-terminal region of Aβ via electrostatic interactions. The N-terminal Aβ domain is also involved in Cu(II)/Cu(I) binding and the formed complexes are known to play a key role in ROS production. In this study, the Aβ–LYC interaction in the absence and in the presence of copper ions was investigated by using the N-terminal Aβ peptide encompassing the first 16 residues. NMR analysis showed that Aβ can simultaneously interact with Cu(II) and LYC. The Cu(II) binding mode remains unchanged in the presence of LYC, while LYC association is favored when an Aβ–Cu(II) complex is formed. Moreover, UV-VIS studies revealed the ability of LYC to interfere with the catalytic activities of the Aβ–Cu(II) complexes by reducing the ascorbate consumption monitored at 265 nm. Full article