Inorganics, Volume 11, Issue 9 (September 2023) – 28 articles

Novel organometallic complexes Mn(benzene-1,2-diamine)(CO)₃Br, Mn-1, Mn(3-methylbenzene-1,2-diamine)(CO)₃Br, Mn-2, and Re(benzene-1,2-diamine)(CO)₃Cl, Re-1, have been synthesized and characterized by IR, UV/Vis, ¹H-NMR, EA and HRMS. The structures of Mn-2 and Re-1 were confirmed by X-ray crystallography. The three novel compounds were studied for their electrocatalytic reduction of carbon dioxide to carbon monoxide using cyclic voltammetry in acetonitrile solutions. Controlled potential electrolysis was used to obtain information on faradaic yield, with product formation being confirmed by GC. Using earth-abundant manganese, compounds Mn-1 and Mn-2 display turnover frequencies of 108 s⁻¹ and 82 s⁻¹, respectively, amid selective production of carbon monoxide (faradaic yields ~85%), with minimal co-production of dihydrogen (<2%), and low overpotential of 0.18 V. The rhenium congener, Re-1, displays no activity as an electrocatalyst for carbon dioxide reduction under identical conditions. Full article

This paper is devoted to the synthesis and application of CdTe quantum dot (QD) nanoparticles covered with organic ligands containing a thiol group, mostly mercaptopropionic acid (MPA) and glutathione (GSH). The simple one-step synthetic procedure was optimized to prepare greater quantities of nanoparticles for analytical purposes. The prepared CdTe QD nanoparticles were characterized by various analytical techniques, and their interaction with some metal ions (Cu(II), Pb(II), and Hg(II)) was studied by using luminescence spectroscopy in both steady-state and time-resolved modes. The mathematical analysis of the quenching effect of Cu(II) ions on the luminescence of CdTe QD nanoparticles shows that the static contribution is mostly responsible for the overall effect, but experimental conditions, such as pH, ionic strength, or the concentration of nanoparticles in aqueous solution, could also be important. The presence of metal ions in the form of a metal complex species could play an important role, and this phenomenon could be used to tune the selectivity of the quenching process. These findings have been utilized for the development of an analytical procedure for the detection and quantitative analysis of Cu(II) and Pb(II) ions in environmental water samples. In practice, this procedure could be easily implemented in a microplate format to increase throughput. Full article

Ruthenium complexes of phosphinocarboxamide ligands, and their use to form metallacycles using halide abstraction/deprotonation reactions are reported. Thus, [Ru(p-cym){PPh₂C(=O)NHR}Cl₂; R = ⁱPr (1), Ph (2), p-tol (3)] and [Ru(p-cym){PPh₂C(=O)N(R)C(=O)N(H)R}Cl₂; R = Ph (4), p-tol (5)] were synthesized from [(p-cym)RuCl₂]₂ (p-cym = para-cymene) and phosphinocarboxamides or phosphinodicarboxamides, respectively. Single-crystal X-ray diffraction measurements on 1–5 reveal coordination to ruthenium through the phosphorus donor, with an intramolecular hydrogen bond between the amine-bound proton and a metal-bound chloride. Six-membered metallacycles formed by halide abstraction/deprotonation of complexes 4 and 5 afforded [Ru(p-cym){κ²-P,N-PPh₂C(=O)N(R)C(=O)NR}Cl] [R = Ph (6), p-tol (7)]. These species exist as a mixture of two rotational isomers in solution, as demonstrated by NMR spectroscopy. Full article

A series including single and mixed Ni-Co aluminates was obtained using the precursor method, with malic acid as a ligand. The malate precursors (polynuclear coordination compounds) were isolated and characterized by Fourier Transform Infrared (FTIR), Ultraviolet/Visible/Near Infrared (UV–Vis–NIR) spectroscopy, and thermal analysis. The UV–Vis–NIR spectra of the synthesized complex compounds highlighted the presence of Co²⁺ and Ni²⁺ in an octahedral environment. The thermal decomposition of these precursors led to Co_1−xNi_xAl₂O₄ (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, and 1) spinels. The effect of Ni²⁺ substitution on the structure, morphology, and optical properties of the obtained oxides was studied with the help of different characterization tools. XRD, FTIR, and Raman spectra evidenced the formation of the spinel phase. The size of the crystallites and the agglomeration degree of the particles decrease when the nickel content increases. The band gap (BG) value is not significantly influenced by the Ni substitution. The fluorescence spectra recorded for all samples show a similar pattern, but different intensities of the emission bands. Full article

An ultrasound-assisted probe sonication route effectively prepared pure CuO and two-dimensional CuO-ZnO nanocomposites (NCs) for different ratios of CuO and ZnO, and the experimental and theoretical methods investigated the structural, photocatalytic, and electrochemical properties. The XRD (X-ray diffraction) patterns revealed a crystallite size (D) range of 25 to 31 nm for pure CuO and CuO-ZnO NCs. According to calculations, the sample’s optical energy bandgap value (Eg) for the NCs is between 1.72 and 2.15 eV. Under UV light irradiation, the photocatalytic discoloration of pure CuO and CuO-ZnO NCs on fast blue (FB) dye was assessed. Under the influence of UV light, the CuO with 10% ZnO composite degrades 83.4% of the dye, which is greater than pure CuO and other NCs. The electrochemical properties of the prepared NCs materials have been studied using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The specific capacitance values were found to be 248 Fg⁻¹, 301 Fg⁻¹, 352 Fg⁻¹, and 277 Fg⁻¹ for CuO, CuO + 5% ZnO, CuO + 10% ZnO, and CuO + 15% ZnO, respectively, at 1 A/g current density. Galvanostatic charge–discharge tests for these designed NCs show excellent capacitance performance in supercapacitors applications. These innovative results could be considered for expanding novel resources to scale for dual applications in photocatalysis and supercapacitors. Full article

A magnesium–aluminum-layered double hydroxide (Mg-Al LDH) with a nano-lamellar morphology was prepared by using a homogeneous precipitation and hydrothermal method, and a calcination product (Mg-Al LDO) of the Mg-Al LDH was also obtained in this work. The XRD, TEM, SEM, FTIR, N₂ ad/desorption, and TG-DTG techniques were employed to characterize the microstructures, morphologies, and thermostability levels of these two materials in detail. The results showed that both the Mg-Al LDH and Mg-Al LDO had mesoporous structures and nanoplate morphologies, with diameters of 50~200 nm. The Mg-Al LDH was transformed into Mg-Al LDO at 773 K in an air atmosphere. The adsorption properties of the Mg-Al LDH were investigated systematically with a copper chloride solution as a simulated waste. The experimental results demonstrated that the pH value of the solution had an obvious influence on its Cu²⁺ adsorption capacity, and the optimal pH value was approximately 5.0. The adsorption kinetics results showed that the Mg-Al LDH had a rapid adsorption rate, and the equilibrium adsorption capacity was 62.11 mg/g. Additionally, the Cu²⁺ adsorption could be commendably described using a pseudo-second-order model, demonstrating that the adsorption behavior is regulated by chemical sorption. The adsorption thermodynamic results indicated that the adsorption process was spontaneous at temperatures above 318 K. Moreover, the ΔG⁰ values decreased as the temperature was raised, which indicated that a higher temperature can cause a greater impetus for Cu²⁺adsorption. In addition, the positive values of the ΔH⁰ indicated that the Cu²⁺ adsorption was endothermic, and the positive ΔS⁰ values revealed an increase in the confusion at the solid–liquid interface of the adsorbent. Full article

Cobalt blue ceramic pigments mainly consisting of CoAl₂O₄ are subject to the difficulty of color control. Here, a perspective is reported regarding research on the reasons for color change based on the control of the heat treatment and ratio of components. Macroscopically, the composition of pigment powders determines the color. Microscopically, the crystallite characters including size, cation distribution, and structure have an important effect on the color. The ingredient, structural, and color properties of the pigment powders are analyzed using thermo gravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD) measurement, Rietveld refinement, energy dispersive spectrometer (EDS), and colorimetry analysis. The color is proven to be associated with cation distribution, such as that of Co²⁺ and Co³⁺. It is indicated that high heating temperature, long heating time, and a large proportion of Al³⁺ can, respectively, induce the Co²⁺ and Al³⁺ in tetrahedral and octahedral sites. Full article

Four new Cu/PPh₃/naphtoquinone complexes were synthesized, characterized (IR, UV/visible, 1D/2D NMR, mass spectrometry, elemental analysis, and X-ray diffraction), and evaluated as anticancer agents. We also investigated the reactive oxygen species (ROS) generation capacity of complex 4, considering the well-established photochemical property of naphthoquinones. Therefore, employing the electron paramagnetic resonance (EPR) “spin trap”, 5,5-dimethyl-1-pyrroline N-oxide (DMPO) technique, we identified the formation of the characteristic •OOH species (hydroperoxyl radical) adduct even before irradiating the solution containing complex 4. As the irradiation progressed, this radical species gradually diminished, primarily giving rise to a novel species known as •DMPO-OH (DMPO + •OH radical). These findings strongly suggest that Cu(I)/PPh₃/naphthoquinone complexes can generate ROS, even in the absence of irradiation, potentially intensifying their cytotoxic effect on tumor cells. Interpretation of the in vitro cytotoxicity data of the Cu(I) complexes considered their stability in cell culture medium. All of the complexes were cytotoxic to the lung (A549) and breast tumor cell lines (MDA-MB-231 and MCF-7). However, the higher toxicity for the lung (MRC5) and breast (MCF-10A) non-tumoral cells resulted in a low selectivity index. The morphological analysis of MDA-MB-231 cells treated with the complexes showed that they could cause decreased cell density, loss of cell morphology, and loss of cell adhesion, mainly with concentrations higher than the inhibitory concentration of 50% of cell viability (IC₅₀) values. Similarly, the clonogenic survivance of these cells was affected only with concentrations higher than the IC₅₀ values. An antimigratory effect was observed for complexes 1 and 4, showing around 20–40% of inhibition of wound closure in the wound healing experiments. Full article

Soluble noble metal salts are widely used for loading noble metals as nano-catalysts in many applications. In this paper, Pt-SnO₂ composite nanoceramics were prepared from SnO₂ nanoparticles and H₂PtCl₆ using two Pt loading methods separately: for the solution reduction method, a H₂PtCl₆ solution was added to a suspension of SnO₂ and zinc powder to form Pt on SnO₂ nanoparticles, and for the impregnation method, Pt was formed from H₂PtCl₆ in the course of sintering. Although a series of samples prepared using both Pt loading methods showed a solid response to H₂ at room temperature, the ones prepared using the solution reduction method exhibited much better room-temperature hydrogen-sensing characteristics. For two samples of 0.5 wt% Pt and sintered at 825 °C, the response value for the sample prepared using the solution reduction method was 9700 to 1% H₂–20% O₂-N₂, which was much larger than the value of 145 for the sample prepared using the impregnation method. Samples prepared using the two Pt loading methods have similar microstructures characterized via XRD, FESEM, EDS, TEM, and HRTEM. However, the residual chlorine content in those using the impregnation method was higher than those using the solution reduction method according to the analysis. It is proposed that the striking difference in room-temperature hydrogen sensing characteristics among samples prepared using these two different Pt loading methods separately resulted from their different chlorine removal processes. This study demonstrates the importance of a proper method for loading noble metals from their soluble salts as nano-catalysts in many applications. Full article

Some new dichloro- and dibromotriphenylphosphino isonitrile and N-acyclic (NAC) carbene complexes of platinum(II) were synthesized, starting from suitable dinuclear precursors. The reaction of cyclohexylisonitrile with trans-[Pt(μ-X)X(PPh₃)]₂, followed by the addition of N,N-diethylamine afforded the corresponding N-acyclic carbene (NAC)derivatives cis-[PtX₂(PPh₃)(NAC)] in 61–64% isolated yield. The cis geometry was attributed based on the comparison with known structures. The stability of the complexes in pure DMSO, DMSO/H₂O, and DMSO/NaCl_aq mixtures was evaluated. While pure DMSO, as well as DMSO/H₂O, did not affect the nature of either dichloro- or dibromo-compounds, dibromo derivatives were not stable in the presence of chloride ions. Since a high concentration of chloride ions is essential to perform in vitro cell assays, only dichlorocomplexes were tested as cytotoxic agents against HepG2 and human tumor cells. Among the tested complexes, NAC derivatives showed a moderate effect on MSTO-211H. Full article

Heterometallic phosphinidene complexes are appealing species for the construction of novel organophosphorus ligands thanks to the high reactivity expected from the combination of M-P multiple bonding and the intrinsically different electronic and coordination preferences of the distinct metals. In a preliminary study, we found that the heterobimetallic complex [MoReCp(μ-PMes*)(CO)₆] (Mes* = 2,4,6-C₆H₂^tBu₃) reacted with CN(p-C₆H₄OMe) via [2+1]-cycloaddition to form a novel azaphosphallene complex. We have now examined in detail the reactions of the above complex and those of its MoMn analogue with different isocyanides, which turned out to be strongly dependent on experimental conditions and on the size of the substituent at the isocyanide. All the products formed follow from one or several of the following reaction pathways: (i) CO substitution by CNR; (ii) addition of CNR at the group 7 metal centre; and (iii) [2+1] cycloaddition of isocyanide at a Mo=P bond to form azaphosphallene groups, with the former process being dominant in reactions at room temperature and for the Mn system. In contrast, low-temperature reactions of the Re system favoured the addition processes, with the [2+1] cycloaddition at Mo=P bonds only taking place at substrates without metal-metal bonds and when the size of the CNR group does not cause unbearable steric clashes when placed in between the Cp and Mes* groups. Full article

In this work, amorphous and crystalline novel products based on Zr, Mg, and Mn were facilely fabricated through the Pechini sol–gel procedure using inexpensive chemicals and an uncomplicated apparatus. Also, these products showed high efficiency as novel adsorbents in getting rid of basic fuchsin dye from aqueous solutions. The adsorbent, which was fabricated before calcination, was abbreviated as KE. In addition, the adsorbents, which were created at 500 and 700 °C, were designated as KE500 and KE700, respectively. The created adsorbents were characterized using high-level transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), N₂ adsorption/desorption analyzer, and field emission scanning electron microscope (FE-SEM). The XRD showed that the KE adsorbent is amorphous, whereas the KE500 and KE700 adsorbents are mixtures of ZrO₂, MgMn₂O₄, and Mg(Mg_0.333Mn_1.333)O₄ nanostructures. The HR-TEM exhibited that the KE adsorbent consists of very fine irregular shapes, whereas the KE500 adsorbent contains quasi-spherical particles with a mean diameter of 45.16 nm. Furthermore, the HR-TEM exhibited that the KE700 adsorbent consists of polyhedral shapes with a mean diameter of 76.28 nm. Furthermore, the BET surface area of the KE, KE500, and KE700 adsorbents is 67.85, 20.15, and 13.60 m²/g, respectively. Additionally, the elimination of basic fuchsin dye by the KE, KE500, and KE700 adsorbents is exothermic, physical in nature, and follows the pseudo-first-order as well as Langmuir equations. Further, the maximum uptake capabilities of the KE, KE500, and KE700 adsorbents toward basic fuchsin dye are 239.81, 174.83, and 93.19 mg/g, respectively. Full article

We reported herein the synthesis, structure determination and emission properties of a cubic molecular Cd(II) coordination cluster whose faces are composed of 12-MC-4 metallacrown units built up from Cd²⁺ and 2-methylmercaptobenzohydroxamic acid (L^mmbHA), resulting in [Cd^II₁₄(L^mmbHA)₁₂(µ₆−O)(DMF)₁₀](ClO₄)₂·3H₂O. The polynuclear complex obtained was characterised by single crystal X-ray diffraction at 193 K. The bulk sample was also analysed by elemental analysis. UV-Vis and emission spectra of the complex were measured in chloroform, as well as the emission spectra of the ligand for comparison. The results of the emission studies revealed that both the ligand and the complex are weakly emissive. Full article

The differential scanning calorimetry study showed that the double perovskite HoBaCo₂O_6-δ (HBC), depending on its oxygen content, undergoes three phase transitions in the temperature range 298–773 K. Their origin was tentatively explained using the relevant literature data. For the single-phase tetragonal HBC, the oxygen nonstoichiometry dependences on the oxygen partial pressure were investigated by thermogravimetric and flow reactor methods in the intermediate-temperature range of 573–773 K. The proposed defect structure of HBC was successfully verified using the obtained data on its oxygen nonstoichiometry combined with those reported earlier. As a result, the values of the thermodynamic parameters (${∆H}_i^{\circ }$, ${∆S}_i^{\circ }$) of the defect reactions proceeding in HBC were determined. The defect structure of HBC was shown to be similar to that of YBaCo₂O_6-δ (YBC) likely due to similar ionic radii of Ho³⁺ and Y³⁺. Full article

Partial oxidation of methane (POM) is a prominent pathway for syngas production, wherein the hydrogen in syngas product can be recovered directly from the reaction system using a hydrogen (H₂)-permeable membrane. Enhancing the efficiency of this H₂ separation process is a current major challenge. In this study, Ce_0.8Y_0.2O_2-δ-BaCe_0.8Y_0.2O_3-δ (YDC-BCY) hollow fiber (HF) membranes were developed and characterized for their H₂ permeation fluxes. Firstly, YDC and BCY ceramic powders were synthesized using the sol-gel method, followed by the fabrication of YDC-BCY dual-phase ceramic HF membranes using a combined phase inversion–sintering process. Characterization using SEM, powder XRD, EDS, and electrical conductivity tests confirmed the phases of the prepared powders and HF membranes. Well-structured YDC and BCY powders with uniform particle sizes were obtained after calcination at 900 °C. With the addition of 1 wt.% Co₂O₃ as a sintering aid, the YDC-BCY dual-phase HF membrane achieved densification after sintering at 1500 °C. Subsequently, the influences of sweep gas composition and temperature on the hydrogen permeation of the YDC-BCY HF membranes with YDC/BCY molar ratios of 2:1, 3:1, and 4:1 were investigated. At 1000 °C and a sweep-gas flow rate of 120 mL·min⁻¹, the YDC-BCY HF membrane with a YDC/BCY molar ratio of 4:1 exhibited a peak hydrogen flux of 0.30 mL·min⁻¹ cm⁻². There is significant potential for improving the hydrogen permeation of dual-phase ceramic membranes, with future efforts aimed at reducing dense layer thickness and enhancing the membrane material’s electronic and proton conductivities. Full article

In low-molecular-weight Mn superoxide dismutase (SOD) mimics, the ligand plays a key role in tuning the reactivity of the metal center with O₂^•−. We used three ligands differing in their donor sites, flexibility and/or charge, to compare the redox properties and SOD activity of the resulting Mn complexes: 1,3-bis[(pyridin-2-ylmethyl)(propargyl)amino]propane (pypapn), 1,3-bis(pyridin-2-ylmethyleneamino)propane (py₂pn) and 1,4-bis(salicylidenamino)butane (H₂salbn). These ligands afford Mn complexes that, in aqueous solution, exist as mononuclear species [Mn(II)(pypapn)(H₂O)₂]²⁺, [Mn(II)(py₂pn)(H₂O)₂]²⁺ and [Mn(III)(salbn)(H₂O)₂]⁺. The relative reactivity of these compounds with O₂^•− at pH 7.8, [Mn(pypapn)(H₂O)₂]²⁺ > [Mn(salbn)(H₂O)₂]⁺ > [Mn(py₂pn)(H₂O)₂]²⁺, is independent of the redox potential but strongly depends on the ligand flexibility which becomes a critical feature when the reaction occurs through an inner-sphere electron-transfer mechanism. Immobilization was used to isolate and protect the catalyst from dissociation or dimerization during catalysis. [Mn(pypapn)(H₂O)₂]²⁺, with the alkyne group, was covalently grafted to azide functionalized mesoporous silica through click chemistry, while [Mn(py₂pn)(solv)₂]²⁺ and [Mn(salbn)(solv)₂]⁺ were encapsulated in SBA-15 mesoporous silica through ionic exchange. The retention or enhancement of the SOD activity and the improved stability of the covalently attached catalyst and the doubly charged complex encapsulated in the silica pores, make them suitable for use in aqueous media. Full article

The unexpected tetranuclear [Cu₄(DPPT)₂Cl₆] complex was obtained by self-assembly of CuCl₂.2H₂O and (E)-2,4-di(piperidin-1-yl)-6-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)-1,3,5-triazine, (HDPPT) in ethanol. In this tetranuclear [Cu₄(DPPT)₂Cl₆] complex, the organic ligand acts as mononegative chelate bridging two crystallographically independent Cu(II) sites. The DPPT⁻ anion acts as a bidentate ligand with respect to Cu(1), while it is a tridentate for Cu(2). The Cu(1)N₂Cl₃ and Cu(2)N₃Cl spheres have square pyramidal and square planar coordination geometries with some distortion, respectively. Two of the chloride ions coordinating the Cu(1) are bridging between two crystallographically related Cu(1) sites connecting two [Cu₂(DPPT)Cl₃] units together, leading to the tetranuclear formula [Cu₄(DPPT)₂Cl₆]. The packing of the [Cu₄(DPPT)₂Cl₆] complex is dominated by C-H…Cl contacts, leading to one-dimensional hydrogen-bond polymeric structure. According to Hirshfeld surface analysis of molecular packing, the non-covalent interactions H…H, Cl…H, Cl…C, C…H, and N…H are the most significant. Their percentages are 52.8, 19.0, 3.2, 7.7, and 9.7%, respectively. Antimicrobial assessment showed good antifungal activity of the Cu(II) complex against A. fumigatus and C. albicans compared to Ketoconazole as positive control. Moreover, the [Cu₄(DPPT)₂Cl₆] complex has higher activity against Gram-positive bacteria than Gentamycin as positive control. The opposite was observed when testing the tetranuclear [Cu₄(DPPT)₂Cl₆] complex against the Gram-negative bacteria. Full article

In an attempt to fill in the empty Zn position in the “Periodic Table” of 1-methylbenzotriazole (Mebta), reactions between Zn(II) sources and this ligand were carried out. The detailed synthetic studies provided access to complexes [ZnX₂(Mebta)₂] (X = Cl, 1; X = Br, 3; X = I, 4), (MebtaH)₂[ZnCl₄] (2), tet-[Zn(NO₃)₂(Mebta)₂] (5), oct-[Zn(NO₃)₂(Mebta)₂] (6), and [Zn(Mebta)₄](Y)₂ [Y = ClO₄, 7; Y = PF₆, 8]. Solid-state thermal decomposition of 2 leads to 1 in quantitative yield. The structures of 3, 4, 5, 6, and 7 were determined by single-crystal crystallography. The structures of the remaining complexes were proposed based on spectroscopic evidence. In all compounds, Mebta behaves as monodentate ligand using the nitrogen of the position 3 as donor. Complexes 1–4, 7, and 8 are tetrahedral. Complexes 5 and 6 are isostoichiometric and their preparation in pure forms depends on the reaction conditions; in the former the Zn^II atom has a tetrahedral geometry, whereas in the latter the metal ion is octahedral. This case of rare isomerism arises from the monodentate (in 5) vs. bidentate (in 6) coordination of the nitrato groups. Extensive π–π stacking interactions and non-classical H bonds build interesting 3D architectures in the structurally characterized complexes. The compounds were characterized by IR, far-IR, and Raman spectroscopies in the solid state, and the data were interpreted in terms of the structures (known or proposed) of the complexes and the coordination modes of the organic and inorganic ligands involved. The solid-state structures of the complexes are not retained in solution, as proven by NMR (¹H, ¹³C[¹H]) spectroscopy and molar conductivity data. The thermal decomposition study of 1 and 3 leads to stable intermediates with 1:1 stoichiometry, i.e., ZnX₂(Mebta). Based on far-IR spectra, polymeric tetrahedral structures are possible with simultaneous presence of terminal and bridging X⁻ groups. Liquid-phase ab initio (MP2) and gas-phase DFT calculations, performed on Mebta and the nitrato complexes, respectively, shed light on the tendency of Mebta for N3-coordination, and the existence and relative stabilities of 5 and 6. Full article

Aluminum oxide production from aluminum filings, which are a byproduct of several industrial machining processes and cannot be recycled to attain bulk aluminum (Al), is vital due to its wide use in scientific research and industry. The goal of this paper is to produce ultrafine and down-to-the-nanoscale alumina powder (Al₂O₃), starting from a waste Al filings. The microstructure and composition of the starting Al used were investigated using scanning electron microscopy (SEM), which was equipped with an attached energy dispersive spectrometer (EDS) unit. The results of this investigation confirmed that the starting Al was mainly Al–Mg alloy. Al₂O₃ was produced using two routes: The first involved the burning of aluminum hydroxide Al(OH)₃ that was precipitated from aluminum chloride solution (AlCl₃) resulting from dissolving the Al filings in 2M HCl. The second route involved direct precipitation as a reaction product of aluminum chloride with sodium carbonate solution. The Al₂O₃ produced using both routes, as well as the intermediate product Al(OH)₃, were studied by SEM. The results demonstrate that the nanoscale range size was reached after milling of the produced Al₂O₃. Following thorough washing with distilled water, the EDS and the XRD techniques confirmed the formation of Al₂O₃, with no residual salt detected. The EDS results showed that the ratios of Al and O in the produced Al₂O₃ were about 96% of the ideal compound ratios. The XRD analysis also revealed the amorphous structure of the standard and the produced Al(OH)₃, whereas the phases of the produced Al₂O₃ were either crystalline or amorphous. In our study, the Al₂O₃ percentage yield was about 77%, and this value obviously depends on the percentage of Al dross in the original Al filings. Overall, this research provides a novel contribution to the production of alumina powder in the nano-range starting from an aluminum filings byproduct, thereby reducing the dependence on known sources of aluminum. Full article

This research work highlights the tribomechanical investigations of using a low loading fraction of two ceramics combinations, Alumina (Al₂O₃) and Silicon Carbide (SiC) as reinforcement for Low-density Polyethylene (LDPE) matrix. The hybrid additives with different weight percentages (0.1 + 0.1, 0.25 + 0.25 and 0.5 + 0.5 wt%) were mixed with LDPE matrix and the degree of homogeneity was controlled using double-screw extruder prior to fabricating the composite samples via the injection molding machine. The nanoparticles fillers were characterized by field emission scanning electron microscope (FESEM), EDX and particle size analyzer to check its morphology, composition and size distribution. Thermogravimetric analyzer (TGA) and melting flow index (MFI) were performed for the fabricated nanocomposites samples. The mechanical properties of the nanocomposite were evaluated by performing tensile test, bending test and Shore-D hardness test, while the tribological performance was investigated using a ball on desk apparatus under different applied loads and sliding times. Moreover, in order to confirm the load-carrying capability of the composite, contact stresses was measured via finite element model using ANSYS software. The results show that the incorporation of low fraction hybrid ceramic nanoparticles can contributed positively in the tribological and mechanical properties. Based on the experimental results, the maximum improvement in the tensile strength was 5.38%, and 8.15% for hardness LDPE with 0.5 Al₂O₃ and 0.5 SiC, while the lowest coefficient of friction was noticed under normal load of 10 N, which was approximately 12.5% for the same composition. The novel approach of incorporating low fraction hybrid ceramic nanoparticles as reinforcement for LDPE matrix is investigated, highlighting their positive contributions to the tribological and mechanical properties of the resulting nanocomposites. Full article

Pyrazino-phenanthroline ligands are commonly used with transition metals as DNA intercalation agents. Herein, we report the characterization of two commonly utilized pyrazino-phenanthroline ligands, dipyrido[3,2-f:2′,3′-h]quinoxaline (dpq) and (benzo[i]dipyrido[3,2-a:2′,3′c]phenazine (dppn), by single-crystal X-ray diffraction. Additionally, the characterization of [Ir(ppy)₂(dppn)][PF₆], where Hppy = 2-phenylpyridine, by single-crystal X-ray diffraction is described. Both the dpq and dppn ligands crystallize as chloroform solvates where the chloroform molecule occupies the equivalent binding pocket of a metal in metal complexes of these ligands. These pyrazino-phenanthrolines are largely planar, with the dppn ligand displaying a slight twist. When the dppn ligand is coordinated to iridium(III), the dppn ligand on the resulting complex displays a significant degree of bending along the longitudinal direction of the ligand. This iridium (III) complex crystallizes as a CH₂Cl₂ and Et₂O solvate and due to the volatility of these solvents these crystals are only stable for a few seconds outside of the mother liquor. The structures of the free ligands and the [Ir(ppy)₂(dppn)][PF₆] complex all display extensive π stacking interactions. Full article

Copper/sulfur co-doped titanium dioxide-carbon nanofibers (Cu,S-codoped TiO₂ NPs, decorated-CNFs) catalysts were synthesized using the electrospinning process to produce composite nanofibers (NFs). These composite NFs were utilized for the hydrolysis of sodium borohydride (SBH) to generate hydrogen gas (H₂), taking advantage of their catalytic properties. The experimental results demonstrated that using 100 mg of composite NFs yielded the highest catalytic activity for H₂ production, generating 79 mL of H₂ gas within 6 min at 25 °C and 1000 revolutions per minute (rpm) using 1 mmol of SBH. As the catalyst dosage was reduced from 100 mg to 75, 50, and 25 mg, the reaction time increased by 9, 13, and 18 min, respectively. Kinetic studies revealed that the reaction rate followed a first-order reaction, indicating a direct proportionality between the rate of reaction and the catalyst amount. Additionally, it was observed that the concentration of SBH had no influence on the reaction rate, suggesting a zero-order reaction. Increasing the reaction temperature resulted in a reduced reaction time. The activation energy was determined to be 26.16 kJ mol⁻¹. The composite NFs maintained their superior performance over five iterations. These findings suggest that composite nanofibers have the potential to serve as a cost-effective alternative to expensive catalysts in hydrogen production. Full article

Reported are the synthesis and structural characterization of a series of quaternary lithium-alkaline earth metal alumo-silicides and alumo-germanides with the base formula A₂LiAlTt₂ (A = Ca, Sr, Ba; Tt = Si, Ge). To synthesize each compound, a mixture of the elements with the desired stoichiometric ratio was loaded into a niobium tube, arc welded shut, enclosed in a silica tube under vacuum, and heated in a tube furnace. Each sample was analyzed by powder and single-crystal X-ray diffraction, and the crystal structure of each compound was confirmed and refined from single-crystal X-ray diffraction data. The structures, despite the identical chemical formulae, are different, largely dependent on the nature of the alkaline earth metal. The differing cation determines the structure type—the calcium compounds are part of the TiNiSi family with the Pnma space group, the strontium compounds are isostructural with Na₂LiAlP₂ with the Cmce space group, and the barium compounds crystallize with the PbFCl structure type in the P4/nmm space group. The anion (silicon or germanium) only impacts the size of the unit cell, with the silicides having smaller unit cell volumes than the germanides. Full article

The [Ag(3ADMT)(NO₃)]_n complex was synthesized by the self-assembly of 3-amino-5,6-dimethyl-1,2,4-triazine (3ADMT) and AgNO₃. Its molecular structure was analyzed utilizing FTIR spectra, elemental analysis, and single crystal X-ray diffraction (SC-XRD). There is one crystallographically independent Ag atom, which is tetra-coordinated by two nitrogen atoms from two 3ADMT and two oxygen atoms from two nitrate anions where all ligand groups are acting as connectors between the Ag1 sites. The geometry around the Ag(I) center is a distorted tetrahedron with a AgN₂O₂ coordination sphere augmented by strong argentophilic interactions between Ag atoms, which assist the aggregation of the complex units in a wavy-like and coplanar pattern to form a one-dimensional polymeric chain. The O...H (37.2%) and N...H (18.8%) intermolecular interactions contributed significantly to the molecular packing based on Hirshfeld surface analysis. The [Ag(3ADMT)(NO₃)]_n complex demonstrates promising cytotoxicity against lung (IC₅₀ = 2.96 ± 0.31 μg/mL) and breast (IC₅₀ = 1.97 ± 0.18 μg/mL) carcinoma. This remarkable cytotoxicity exceeds those of 3ADMT, AgNO₃, and the anticancer medication cis-platin towards the tested cancer cell lines. In addition, the complex has a wide-spectrum antimicrobial action where the high antibacterial potency of the [Ag(3ADMT)(NO₃)]_n complex against P. vulgaris (MIC = 6.1 µg/mL) and B. subtilis (MIC = 17.2 µg/mL) could be comparable to the commonly used drug Gentamycin (MIC = 4.8 µg/mL). These results confirm that the components of the [Ag(3ADMT)(NO₃)]_n complex work together synergistically, forming a powerful multifunctional agent that could be exploited as an effective antimicrobial and anticancer agent. Full article

The reactivity of the open-shell Gd@C_2v-C₈₂ with different charge states towards benzyl bromide was investigated. [Gd@C_2v-C₈₂]³⁻ exhibited enhanced activity relative to Gd@C_2v-C₈₂ and [Gd@C_2v-C₈₂]⁻. The structural characterizations, including MALDI-TOF MS, UV-vis-NIR, and single crystal X-ray diffraction, indicate the formation of isomeric benzyl monoadducts of Gd@C_2v-C₈₂. All three monoadducts contain 1:1 mirror-symmetric enantiomers. Additionally, the addition of the benzyl group and its specific position result in distinct electrochemical behavior of the products compared to the parent Gd@C_2v-C₈₂. Theoretical studies demonstrate that only [Gd@C_2v-C₈₂]³⁻ has a HOMO energy level that matches well with the LUMO energy level of the PhCH₂ radical, providing a rationalization for the observed significantly different reactivity. Full article

Multicopper active sites for small molecule activation in materials and enzymatic systems rely on controlled but adaptable coordination spheres about copper clusters for enabling challenging chemical transformations. To translate this constrained flexibility into molecular multicopper complexes, developments are needed in both ligand design for clusters and synthetic strategies for modifying the cluster cores. The present study investigates the chemistry of a class of pyridyldiimine-derived macrocycles with geometrically flexible aliphatic linkers of varying lengths (ⁿPDI₂, n = 2, 3). A series of dicopper complexes bound by the ⁿPDI₂ ligands are described and found to exhibit improved solubility over their parent analogs due to the incorporation of 4-^tBu groups on the pyridyl units and the use of triflate counterions. The ensuing synthetic study investigated methods for introducing various bridging ligands (µ-X; X = F, Cl, Br, N₃, NO₂, OSiMe₃, OH, OTf) between the two copper centers within the macrocycle-supported complexes. Traditional anion metathesis routes were unsuccessful, but the abstraction of bridging halides resulted in “open-core” complexes suitable for capturing various anions. The geometric flexibility of the ⁿPDI₂ macrocycles was reflected in the various solid-state geometries, Cu–Cu distances, and relative Cu coordination spheres on variation in the identity of the captured anion. Full article

This article focuses on the galvanic replacement synthesis of Ti-Ni and Zr-Ni metal systems with a “core-shell” structure, which are potential precursors for intermetallics. The authors defined effective synthesis parameters and formation features of polymetallic systems characterized by granulometric, phase, and elemental composition. X-ray fluorescence and X-ray phase analysis methods showed that the deposition of nickel on dispersed titanium and zirconium leads to the production of test samples with phase composition representing a mechanical mixture of Ni and Ti, and Ni and Zr. The method of X-ray fluorescence analysis showed that the presence of hydrofluoric acid with a 0.5-1.5 M concentration results in the formation of fixed quantitative ratios of elements in the precipitate, which allows the quantitative composition of dispersed systems “titanium-nickel” and “zirconium-nickel” to be regulated within a relatively wide range. Scanning electron microscopy proved that all synthesized systems are characterized by a highly porous structure that follows the titanium and zirconium particle surface contour and the presence of spherical nanoscale subunits on the formed particle surface. Full article