Inorganics, Volume 11, Issue 11 (November 2023) – 30 articles

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

For decades, amyloid β-peptide (Aβ) misfolding aggregates with β-sheet structures have been linked to the occurrence and advancement of Alzheimer’s disease (AD) development and progression. As a result, modulating the misfolding mode of Aβ has been regarded as an important anti-amyloid protein misfolding strategy. A polyoxometalate based on {Co(H₂O)₄}²⁺ complex and [P₂Mo₅O₂₃]⁶⁻ fragments, K₈{[Co(H₂O)₄][HP₂Mo₅O₂₃]₂}·8H₂O (abbreviated as CoPM), has been synthesized and structurally characterized using elemental analysis, single-crystal X-ray diffraction (SXRD), IR, UV spectra, bond valence sums (Σs) calculation, and powder XRD (PXRD). CoPM’s primary component, as revealed by structural analysis, is a nanoscale polyoxoanion made of [Co(H₂O)₄]²⁺ sandwiched between two [P₂Mo₅O₂₃]⁶⁻ pieces. Notably, it is demonstrated that CoPM efficiently modulates Aβ aggregates’ β-sheet-rich conformation. Full article

In the past decade, there have been significant advancements in the investigation of coherence-related phenomena in organic systems such as biological photosynthetic reaction centers. The d⁸ Pt(II) dinuclear complex or molecular aggregate with a metal–metal-to-ligand charge transfer (MMLCT) or metal-centered (MC) excited state was reported to show the vibrational coherence phenomenon in the intersystem crossing (ISC) process, due to the Metal–metal (M-M) interaction at excited state. In this study, we review the coherence effect in the Pt(II)-Pt(II) complexes which are speculated to be a coherent energy conversion system. The impacts of coherence on the photo-physics of Pt(II) dinuclear complexes have been discussed and reviewed, including the intersystem crossing process and vibrational wavepacket dynamics. Full article

Practical applications of Li-metal anodes are limited by dendrite formation, Li loss, and poor reaction, resulting in a low Coulombic efficiency. In this study, we investigated the effects of island-shaped Ag atoms on the electrochemical behavior of Li-metal anodes. A Ag–Cu film was co-deposited through sputtering and subsequent annealing to anchor the Ag atoms with an island shape on a Cu substrate. The Ag target was co-sputtered with Cu with controlled atomic ratios in the Ag–Cu alloy. The sputtering thickness was set to 100 nm, and various annealing conditions were applied. The embedded island-shaped Ag atoms provided effective nucleation sites for Li deposition during the electrochemical nucleation of Li, increasing the nucleation density and spatial uniformity while decreasing the nucleation size and potential. Compact dendrite-free high-density Li deposition was achieved by annealing the Ag–Cu current collector (CC) at 600 °C. Under repetitive Li plating and stripping for 110 cycles at a current density of 0.5 mAcm⁻² and capacity of 1 mAhcm⁻², a high Coulombic efficiency of 98.5% was achieved. Conversely, the bare Cu CC had a life of up to 67 cycles under the same test conditions. Full article

In the present work, the photodegradation performances of N-doped TiO₂ photocatalysts with enhanced absorption of visible light were exploited for the abatement of some representative contaminants of emerging concern (CECs). Pristine TiO₂ and N-TiO₂ were synthesized using hydrothermal (HT) and sol–gel (SG) routes, they were characterized using XRD and UV-Vis spectroscopy, and their band gaps were determined via analysis in diffuse reflectance. Their photodegradation efficiency was tested on a mixture of recalcitrant organic pollutants, namely, benzotriazole, diclofenac, sulfamethoxazole, and bisphenol A, using a solar simulator lamp with two different cut-off filters (λ > 340 nm and λ > 400 nm). The evaluation of the photocatalytic performances was initially carried out in spiked ultrapure water and subsequently in aqueous matrices of increasing complexity such as Po River water and water coming from an aquaculture plant. The exclusive utilization of visible light (λ > 400 nm) highlighted the advantage of introducing the dopant into the TiO₂ photocatalyst since this modification allows for the material to be responsive to visible light, which is not sufficient in the case of pristine TiO₂ and the higher efficiency of materials obtained via the sol–gel route. Thanks to the doping, improved performance was obtained in both ultrapure water and real water matrices, indicating the potential of the doped material for future applications in the field. Full article

Singlet oxygen (¹O₂), representing an important reactive oxygen species, has promising applications in biomedical, material, and environmental sciences. Photosensitized production of ¹O₂ using organic dyes is highly desirable and the exploration of highly efficient photosensitizers has received considerable attention. Herein, two tridentate Pt(II) complexes, i.e., cationic 1(PF₆) and neutral 2, modified with the ethynylnaphthalimide chromophore, were designed and prepared for the application in ¹O₂ generation. Spectroscopic studies and computational results suggest that 1(PF₆) and 2 display the lowest-energy absorption bands centered at 435–465 nm with the molar extinction coefficients of 0.6–3.2 × 10⁴ M⁻¹ cm⁻¹, originating from the singlet ligand-to-ligand charge transfer (¹LLCT) and a mixture of ¹LLCT and singlet ligand-centered (LC) transitions, respectively. Moreover, they show similar phosphorescence at 620–640 nm assigned to the Pt-perturbed triplet LC emission of the ethynylnaphthalimide moiety. Thanks to the relatively long phosphorescence lifetimes, these complexes exhibit O₂-dependent phosphorescence intensities with good reversibility and stability. They are able to behave as efficient triplet photosensitizers to promote the ¹O₂ generation with high quantum yields (84–89%). This work indicates that the combination of an organic chromophore with Pt(II) complexes provides an effective method to obtain photosensitizers for ¹O₂ generation. Full article

Half-sandwich iron(II) dihalido complexes of the type [Fe(η⁵-Cp’)X₂]⁻ (Cp’ = C₅H₅ or substituted cyclopentadienyl) which are thermally stable at room temperature are extremely scarce, being limited to congeners containing the bulky C₅H₂-1,2,4-tBu₃ ligand. We extended this to homologues [Fe(η⁵-Cp*)X₂]⁻ (X = Cl, Br, I) containing the particularly popular C₅Me₅ (Cp*) ligand. Corresponding ionic compounds ER₄[Fe(η⁵-Cp*)X₂] are easily accessible from FeX₂, MCp* (M = Li, K) and a suitable halide source R₄EX (E = N, P) in THF. Despite their high sensitivity towards air and moisture, the new compounds NnPr₄[Fe(η⁵-Cp*)X₂] (X = Cl, Br), NnPr₄[Fe(η⁵-Cp*)BrCl], and PPh₄[Fe(η⁵-Cp*)X₂] (X = Cl, Br, I) were structurally characterised using single-crystal X-ray diffraction. NnPr₄[Fe(η⁵-Cp*)Cl₂] reacts readily with CO to afford [Fe(η⁵-Cp*)Cl(CO)₂], indicating the synthetic potential of ER₄[Fe(η⁵-Cp*)X₂] in FeCp* half-sandwich chemistry. Full article

During the last two decades, metal-organic cages (MOCs) have been extensively investigated and well documented. Meanwhile, phosphorescent MOCs have emerged as a kind of new MOC material but have not been given much attention. The diversity of their structures and their flexibility of self-assembly result in various luminescent behaviors. Additionally, their special photoactive properties are quite attractive in the background of photochemistry and worthy of discussion. Here, we would like to introduce the recent development of phosphorescent MOCs, including their structures, syntheses, photophysical properties and possible applications. This minireview may hopefully inspire the development of novel phosphorescent MOCs and also facilitate promising applications. Full article

Herein, the structural and photophysical features of two N-based polydentate ligands and the corresponding Zn(II) complexes are investigated. The obtained compounds were characterized using different spectroscopic techniques and their optical properties are discussed in relation to their chemical structure, defined by single-crystal X-ray diffraction and mass spectrometry. The spontaneous and quantitative complexation, investigated by UV-Vis, fluorescence, NMR, IR spectroscopies and mass spectrometry, makes these N-based polydentate ligands interesting candidates for possible applications in chelation therapy and in Zn(II) sensors. Full article

A new polymorphic modification of lanthanum sulfate was obtained by thermal dehydration of the respective nonahydrate. According to powder X-ray diffraction, it was established that β-La₂(SO₄)₃ crystallized in the C2/c space group of the monoclinic system with the KTh₂(PO₄)₃ structure type (a = 17.6923(9), b = 6.9102(4), c = 8.3990(5) Å, β = 100.321(3)°, and V = 1010.22(9) ų). Temperature dependency studies of the unit cell parameters indicated almost zero expansion along the a direction in the temperature range of 300–450 K. Presumably, this occurred due to stretching of the [LaO₉]_n chains along the c direction, which occurred without a significant alteration in the layer thickness over the a direction. A systematic study of the formation and destruction processes of the lanthanum sulfates under heating was carried out. In particular, the decisive impact of the chemical composition and formation energy of compounds on the thermodynamic and kinetic parameters of the processes was established. DFT calculations showed β-La₂(SO₄)₃ to be a dielectric material with a bandgap of more than 6.4 eV. The processing of β-La₂(SO₄)₃ with the Kubelka–Munk function exhibited low values below 6.4 eV, which indicated a fundamental absorption edge above this energy that was consistent with LDA calculations. The Raman and infrared measurements of β-La₂(SO₄)₃ were in accordance with the calculated spectra, indicating that the obtained crystal parameters represented a reliable structure. Full article

In the context of investigating isostructural relationships between sulfates and monofluorophosphates, crystals of the double salts (NH₄)₂PO₃F·NH₄NO₃ (AFP·AN) and (NH₄)₂XO₄·3NH₄NO₃ (AX·3AN; X = Se, Cr) were grown from aqueous solutions and structurally characterized using X-ray diffraction and thermal analysis. Whereas the high-temperature forms of the two AX·3AN double salts are in fact isostructural with the sulfate analogue, AFP·AN crystallizes with a reduced amount of NH₄NO₃ and thus has a unique crystal structure. Both AFP·AN and the two AX·3AN compounds exhibit reversible structural phase transitions. Upon cooling, the monofluorophosphate double salt transforms from the monoclinic room-temperature polymorph (I; P2₁/n, Z = 4) to the intermediate triclinic polymorph (II; P1, Z = 4) that in turn transforms to the monoclinic low-temperature polymorph (III; P2₁/n, Z = 4). The two phase transitions (I) → (II) and (II) → (III) are characterized by a significant increase of the unit cell volumes upon cooling. The two AX·3AN double salts transform upon cooling from a disordered monoclinic crystal structure (P2₁, Z = 2) to a monoclinic polymorph with a doubled unit cell (P2₁/c, Z = 4). Such a phase transition is not observed for the sulfate analogue. All molecular moieties are fully ordered at −93 °C for the selenate double salt, whereas one of the nitrate anions remains disordered for the chromate double salt even at −173 °C. In all AFP·AN and AX·3AN crystal structures, the nitrate anions play a crucial role during the phase transitions, and an extensive network of N–H···O hydrogen-bonding interactions is responsible for the cohesion of the crystal. Full article

In this study, the synthesis of a Schiff base containing metal–organic frameworks (MOFs) of the UiO-67 family has been investigated. MOFs featuring free amine groups were successfully synthesized under mild solvothermal conditions using 2-amino-[1,1′-biphenyl]-4,4′-dicarboxylic acid and 2,2′-diamino-[1,1′-biphenyl]-4,4′-dicarboxylic acid as bridging ligands, resulting in MOFs with amine groups covalently linked to the bridging ligands. Both types of functionalized MOFs were post-synthetically modified with 4-formylbenzonitrile that resulted in imine formation. All the obtained compounds were characterized by PXRD, TGA, DTA, BET, NMR, and FTIR spectroscopy, while stability in water was monitored with SEM, EDS, and UV–VIS spectroscopy. Full article

Fe-S clusters are essential cofactors for the activity of a large variety of metalloproteins that play important roles in respiration, photosynthesis, nitrogen fixation, regulation of gene expression, and numerous metabolic pathways, including biosynthesis of other protein cofactors. Assembly of iron and sulfur atoms into a cluster, followed by its insertion into the polypeptide chain, is a complex process ensured by multiproteic systems. Through evolution, eukaryotes have acquired two Fe-S protein biogenesis systems by endosymbiosis from bacteria. These systems, ISC and SUF, are compartmentalized in mitochondria and plastids, respectively. The eukaryotic Fe-S protein biogenesis system (CIA) is dedicated to the biogenesis of cytosolic and nuclear Fe-S proteins. While the CIA system is absent in bacteria, at least two of its components share homologies with bacterial Fe-S protein biogenesis factors, Mrp and SufT. Here, we provide an overview of the role of Mrp and SufT in Fe-S protein biogenesis in bacteria, aiming to put forward specific but also common features with their eukaryotic CIA counterparts. Full article

Silica nanostructured materials find application in different fields, since they are cheap, versatile, and easy to functionalize as materials. However, silica reactivity has not been deeply investigated yet, mainly due to a poor understanding of how it is affected by superficial defects. In the present study, the electronic and optical properties of nanoparticles have been investigated using bare silica nanoparticles (SNP) and amino- or phosphonate-functionalized silica nanoparticles (SNP–APTES and SNP-phosphonate), prepared by a sol-gel procedure, and their morphology has been investigated using transmission electron microscopy (TEM) analysis. The prepared silica nanomaterials were characterized by means of reflectance and emission spectroscopies to determine the types of defects that can be found on silica nanoparticles’ surface. In order to understand the effect of surface defects on the reactivity of silica, the nanoparticles were employed for the photocatalytic degradation of Rhodamine 6G (R6G), upon selective irradiation at 320 nm, where only silica colloids absorb. The photoreaction was carried out in ethanol and in water and was monitored following the fluorescence signal of the dye. The evaluation of the fluorescent intensities allowed for the determination of the degradation efficiencies. Full article

The emergence of drug resistance due to the overuse of antibiotics has made the prevention and treatment of invasive fungal infections caused by Candida albicans (C. albicans) a great challenge. Oxygen vacancy-rich inorganic materials show great promise in the antimicrobial field due to their unique physicochemical properties. Defect engineering can significantly optimize the electronic structure of inorganic materials to further enhance their antimicrobial activity. We designed oxygen vacancy defect-rich V₆O₁₃ powders using the hydrothermal-calcination method and investigated their anti-C. albicans activity. The results showed that the stronger antibacterial activity is attributed to the fact that the optimized V₆O₁₃ powder oxygen vacancy defects induced a reduction reaction of dissolved oxygen in the environment, which produced ROS with strong oxidative properties, causing damage to the wall membrane of C. albicans and leakage of intracellular material. The minimum inhibitory concentration (99% or more inhibition) of V₆O₁₃ powders is 4 mg/mL. This work not only provides a facile method for constructing oxygen-rich vacancies in V₆O₁₃ powders, but also provides new insights into the potential of inorganic materials optimized by defect engineering for efficient antimicrobial activity. Full article

Arsenic is highly toxic, affecting millions of people in many regions of the world. That is why developing economic and efficient technologies is imperative to eliminate it. Sorption techniques are attractive as efficient and inexpensive sorbents can be used. Chitosan is an abundant, naturally occurring, biodegradable, low-cost biopolymer that can be combined with metal oxide to enhance its removability. This work aimed to synthesize a new chitosan–magnetite-based sorbent for arsenic removal. The synthesized sorbent does not present pores, and when using FT-IR, functional groups of the chitosan and the presence of As(V) in the sorbent treated with arsenic were identified. The synthesized magnetite was characterized using XRD spectroscopy. Application of the central composite design model showed that 0.22 g of the sorbent at pH 6.0 could remove 27.6% of As(V). Kinetic data, fitted with the pseudo-first and -second order models, indicated an ion exchange sorption and activation energy of 28.1–31.4 kJ mol⁻¹. The isotherms were fitted with the Langmuir model, indicating favorable monolayer adsorption with high affinity. The sorption energy calculated using Dubinin Radushkevich, 9.60–8.80 kJ mol⁻¹, confirms a sorption mechanism mediated by ion exchange. The thermodynamic parameters of the process were ΔG° (−21.7/−19.7 kJ mol⁻¹), ΔH°(16.7 kJ mol⁻¹) and ΔS°(123.3 J mol⁻¹ K⁻¹). Full article

Hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂)-based porous scaffolds have been widely investigated in the last three decades. HA, with excellent biocompatibility and osteoconductivity, has made this material widely used in bone tissue engineering. To improve the mechano-biological properties of HA, the addition of clay to develop HA-based composite scaffolds has gained considerable interest from researchers. In this study, a cost-effective method to prepare a HA–clay composite was demonstrated via the mechanical mixing method, wherein kaolin was used because of its biocompatibility. Prawn (Fenneropenaeus indicus) exoskeleton biowaste was utilized as a raw source to synthesize pure HA using wet chemical synthesis. HA–clay composites were prepared by reinforcing HA with 10, 20, and 30 wt.% of kaolin via the mechanical mixing method. A series of characterization tools such as XRD, FTIR, Raman, and FESEM analysis confirmed the phases and characteristic structural and vibrations bonds along with the morphology of sintered bare HA, HA–kaolin clay composite, and kaolin alone, respectively. The HA–clay composite pellets, uniaxially pressed and sintered at 1100 °C for 2 h, were subjected to a compression test, and an enhancement in mechanical and physical properties, with the highest compressive strength of 35 MPa and a retained open porosity of 33%, was achieved in the HA–kaolin (20 wt.%) clay composite, in comparison with bare HA. The addition of 20% kaolin to HA enhanced its compressive strength by 33.7% and increased its open porosity by 19% when compared with bare HA. The reinforcement of HA with different amounts (10, 20, 30 wt.%) of kaolin could open up a new direction of preparing biocomposite scaffolds with enhanced mechanical properties, improved wear, and better cell proliferation in the field of bone tissue engineering. Full article

The direct incorporation of Sb(V) ions into a polycondensed silsesquioxane network based on heptaisobutyl POSS units (Sb(V)-POSSs) through a corner-capping reaction is reported for the first time in this work. As a reference sample, a completely condensed monomeric Sb(III)-POSS was prepared using a similar synthetic protocol. The chemical properties of both Sb-containing POSSs were investigated with different analytical and spectroscopic techniques. The analyses confirm the success of the corner-capping reaction for both samples and indicate that an Sb(V)-POSS sample is characterized by a heterogenous multimeric arrangement with an irregular organization of POSS cages linked to Sb(V) centers, and has a more complex structure with respect to the well-defined monomeric Sb(III)-POSS. Full article

The Cu(II)/Cu(I) conversion involves variation in the coordination number and geometry around the metal center. Therefore, the flexibility/rigidity of the ligand plays a critical role in the design of copper superoxide dismutase (SOD) mimics. A 1,3-Bis[(pyridin-2-ylmethyl)(propargyl)amino]propane (pypapn), a flexible ligand with an N₄-donor set, was used to prepare [Cu(pypapn)(ClO₄)₂], a trans-Cu(II) complex whose structure was determined by the X-ray diffraction. In DMF or water, perchlorate anions are exchanged with solvent molecules, affording [Cu(pypan)(solv)₂]²⁺ that catalyzes O₂^•− dismutation with a second-order rate constant k_McF = 1.26 × 10⁷ M⁻¹ s⁻¹, at pH 7.8. This high activity results from a combination of ligand flexibility, total charge, and labile binding sites, which places [Cu(pypapn)(solv)₂]²⁺ above other mononuclear Cu(II) complexes with more favorable redox potentials. The covalent anchoring of the alkyne group of the complex to azide functionalized mesoporous silica through “click” chemistry resulted in the retention of the SOD activity and improved stability. A dicationic Cu(II)-N₄-Schiff base complex encapsulated in mesoporous silica was also tested as an SOD mimic, displaying higher activity than the free complex, although lower than [Cu(pypapn)(solv)₂]²⁺. The robustness of covalently attached or encapsulated doubly charged Cu(II) complexes in a mesoporous matrix appears as a suitable approach for the design of copper-based hybrid catalysts for O₂^•− dismutation under physiological conditions. Full article

Emerging as a new class of advanced functional materials with hierarchical architectures and redox characters, organic–inorganic hybrid materials (OIHs) have been well developed and widely applied in various energy conversion reactions recently. In this review, we focus on the applications and structure–performance relationship of OIHs for electrochemical water oxidation. The general principles of water oxidation will be presented first, followed by the progresses on the applications of OIHs that are classified as metal organic frameworks (MOFs) and their derivates, covalent organic framework (COF)-based hybrids and other OIHs. The roles of organic counterparts on catalytic active centers will be fully discussed and highlighted with typical examples. Finally, the challenges and perspectives assessing this promising hybrid material as an electrocatalyst will be provided. Full article

Na-magadiite materials were prepared from a gel containing a silica source, sodium hydroxide, and water via hydrothermal treatment at different temperatures (130 °C to 170 °C) and periods of time (1 day to 10 days). In this study, four silica sources were selected (fumed silica, colloidal silica, Ludox HS-40%, and Ludox AS-40%). Variable conditions such as sodium hydroxide and water contents were explored at a specific temperature and reaction time. The obtained materials were characterized by using X-ray diffraction (XRD), thermogravimetry differential thermal analysis TG-DTA, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Fourier Transform Infrared spectroscopy (FTIR), solid ²⁹Si magic angle spinning magnetic nuclear resonance (MAS MNR, and nitrogen adsorption isotherms. A pure Na-magadiite phase was obtained from the four silica sources at a synthesis temperature of 150 °C after a period of one to two days with a characteristic basal spacing of 1.54 nm. At a longer reaction time of 3 days and a higher temperature of 170 °C, Na-kenyaite with a basal spacing of 2.01 nm was achieved, in addition to a quartz phase. The content of water or sodium hydroxide in the gel affected the nature of the prepared phases. A cauliflower-like morphology was obtained from colloidal silica sources, while a different morphology was achieved using solid fumed silica. The ²⁹Si solid NMR confirmed the presence of Q³ and Q⁴ silicon sites in the Na-magadiite materials. The optimal Na-magadiite materials at 150 °C for 2 days were assessed for their ability to remove Basic Blue-41 dye from artificially contaminated aqueous solution. The Langmuir equation was used to estimate the maximum removal capacity. A maximum removal capacity of 219 mg/g was achieved using Na-magadiite prepared from a Ludox-HS40% silica source, and a maximum removal capacity of 167 mg/g was observed for Na-magadiite prepared from fumed silica. Basic Blue-4’s removal percentage was enhanced at basic pH levels (8 to 10) to a maximum of 95%. These materials could be regenerated for seven cycles of reuse with a reduction of 27 to 40% of the original values. Therefore, Na-magadiite materials are promising and efficient removal agents for the removal of Basic Blue-41 from effluents. Full article

A novel Non-Isolated-Pentagon-Rule (non-IPR) isomer of thorium-based endohedral mono-metallofullerenes (mono-EMFs), Th@C₁(17418)-C₇₆, was successfully synthesized and characterized using MALDI-TOF mass spectroscopy, single-crystal X-ray diffraction, UV-vis-NIR spectroscopy, and Raman spectroscopy. The molecular structure of this non-IPR isomer was determined unambiguously as Th@C₁(17418)-C₇₆ using a single-crystal X-ray diffraction analysis. The crystallographic results further revealed that the optimal Th site resided at the intersection of two adjacent pentagons, similar to that of U@C₁(17418)-C₇₆. Additionally, the UV-vis-NIR spectra of Th@C₁(17418)-C₇₆ exhibited distinct differences compared to the previously reported U@C₁(17418)-C₇₆, highlighting the distinctive electronic structure of actinium-based endohedral metallofullerenes (EMFs). The Raman spectrum of Th@C₁(17418)-C₇₆ exhibited similarities to that previously reported for thorium-based EMFs, indicating the analogous strong metal–cage interactions of thorium-based EMFs. Full article

Sodium chloride (NaCl) represents the principal component of atmospheric particulates of marine origin. To gain a molecular-level understanding of the adsorption process of water vapor on the NaCl surface, Monte Carlo simulations performed in the Grand Canonical ensemble were carried out, considering the water adsorption at different water pressures on a NaCl(001) surface. The calculated adsorption isotherm shows four different regions, whose coverages correspond to those of the low-, transition-, high-, and pre-solution-coverage regions experimentally observed. Detailed analysis reveals how the structure of the adsorbed water molecules (islands, layer, and multi-layer) changes depending on water pressure, and how their orientation with respect to the surface varies with the distance from the surface. This detailed information further supports the picture coming from previous experimental IR absorption spectroscopy studies. Full article

Some copper(II) and zinc(II) complexes with oxindolimine ligands were tested regarding their trypanocidal properties. These complexes have already shown good biological activity in the inhibition of tumor cell proliferation, having DNA and mitochondria as main targets, through an oxidative mechanism, and inducing apoptosis. Herein, we demonstrate that they also have significant activity against the infective trypomastigote forms and the intracellular amastigote forms of T. cruzi, modulated by the metal ion as well as by the oxindolimine ligand. Selective indexes (LC₅₀/IC₅₀) determined for both zinc(II) and copper(II) complexes, are higher after 24 or 48 h incubation with trypomastigotes, in comparison to traditional drugs used in clinics, such as benznidazole, and other metal-based compounds previously reported in the literature. Additionally, tests against amastigotes indicated infection index <10% (% of infected macrophages/average number of amastigotes per macrophage), after 24 or 48 h in the presence of zinc(II) (60–80 µM) or analogous copper(II) complexes (10–25 µM). The copper complexes exhibit further oxidative properties, being able to damage DNA, proteins and carbohydrates, in the presence of hydrogen peroxide, with the generation of hydroxyl radicals. This redox reactivity could explain its better performance towards the parasites in relation to the zinc analogs. However, both copper and zinc complexes display good selective indexes, indicating that the influence of the ligand is also crucial, and is probably related to the inhibition of some crucial proteins. Full article

The reaction of Tb³⁺ ions with KAu(SCN)₂ results in the formation of the crystalline coordination compound Tb[Au(SCN)₂]₃·6H₂O. Single-crystal X-ray diffraction has been employed to investigate the structural features of this compound. The crystallographic data are as follows (Mo K_α, λ = 0.71073 Å): orthorhombic, Cmcm, a = 12.4907(9) Å, b = 8.5845(6) Å, c = 20.7498(8) Å, V = 3679.72(16) ų, Z = 4, R₁(I > 2(σ)) = 0.0232. This material represents the first known example of a lanthanide dithiocyanatoaurate compound. Au(SCN)₂⁻ anions bridge Tb³⁺ centers in a bidentate fashion to form the [Tb(H₂O)₄(Au(SCN)₂)₂]͚⁺ 1D chains present in the structure. Trimeric Au units in the structure contain short aurophilic bonding interactions with distances of 3.1066(4) Å. The more common O–H‧‧‧O and O–H‧‧‧N H-bonding interactions in the structure are overshadowed by relatively rare O–H‧‧‧S interactions involving the bis(thiocyanato)gold(I) anions. Photoluminescence measurements illustrate that Tb[Au(SCN)₂]₃·6H₂O displays strong Tb³⁺-based emission, but there is a lack of Au-based emission down to 85 K. Excitation spectra are recorded for the title compound and these measurements demonstrate the presence of a donor–acceptor process within the compound, leading to enhanced Tb³⁺-based emission. Full article