Abstract:

Microwave heating has a good number of advantages in the synthesis of inorganic compounds when opportunely exploited. A deep knowledge of the interaction of the electromagnetic waves and matter is necessary to optimize irradiation of the reactor vessel so that to obtain homogeneous heating for homogeneous nucleation and growth of particle, localized heating of starting self-sustained high temperature synthesis and generate superfast heating and cooling profile to get metastable crystals. Case studies of pure oxides, mixed oxides, composites, phosphates, zeolites, and high entropy alloys have been discussed in the international frame of the academic and industrial research covering the last 20 years of microwave chemistry where Italian researchers covered a relevant role.

Abstract: Platinum-based drugs play a pivotal role in contemporary cancer treatment, but their therapeutic utility is often limited by acquired resistance. The diiodido analogue, cis-PtI2(NH3)2 is a promising derivative that has demonstrated the ability to overcome cis-platin resistance in vitro. To establish the molecular basis for this superior activity, we integrated experimental 14N Nuclear Magnetic Resonance (NMR) spectroscopy with computational density functional theory (DFT) methods to precisely and comparatively understand the drug activation mechanisms. Comparative 14N NMR experiments elucidated the initial ligand substitution step, confirming halide displacement and a markedly higher tendency for ammonia release from cis-PtI2(NH3)2, particularly when reacting with sul-fur-containing amino acids. Complementary DFT calculations determined the substitution energy values, revealing that the superior leaving-group ability of iodide results in a thermodynamically more favorable activation. Conceptual DFT parameters (softness, hardness, and Fukui indices) further demonstrated that initial substitution induces a strong trans effect, leading to the electronic sensitization of the remaining iodide ligand. This strong agreement between computational predictions and experimental data establishes a coherent molecular activation mechanism for cis-PtI2(NH3)2 demonstrating that iodide substitution promotes both thermodynamic and electronic activation of the plati-num center, which is the key to its distinct pharmacological profile and ability to circumvent resistance.

Abstract: This paper presents the synthesis of novel copper(II) metal complex with ethyl 2-(methylcarbamoyl)phenyl) carbamate and 3-methylquinazoline-2,4(1H,3H)-dione. The charac-terization of compound was conducted through various techniques, including melting point de-termination, IR, 1H NMR, and 13C NMR spectroscopy. The coordination compound was obtained after mixing water solutions of the metal salt and the ligand dissolved in DMSO and water solu-tions of NaOH, in metal-to-ligand to base ratio 1:2:2. The ligand and the metal chloride were brought in to reaction at room temperature in DMSO and H2O as solvents, respectively. We as-sume that the ligands are coordinated through N-donor atom. The results indicate the successful formation of a stable mixed-ligand Cu(II) coordination compound involving N-donor ligands. Spectroscopic data suggest that the deprotonated ligand (3-methylquinazoline-2,4(1H,3H)-dione) by using (NaOH) coordinated to metal ion as monodentate ligand through the nitrogen atom of the NH and ethyl 2-(methylcarbamoyl)phenyl) carbamate coordinated as a monodentate through the nitrogen atom of amide group.

Abstract: The synthesis and systematic investigation of inorganic and organic compounds represent a crucial area in medicinal and pharmaceutical chemistry, particularly in the pursuit of novel therapeutic agents. This study reports on the preparation, structural analysis, and evaluation of selected inorganic and organic compounds with emphasis on their physicochemical characteristics and biological activities. Both categories of compounds were examined for their potential therapeutic relevance, including anticancer, antimicrobial, and anti-inflammatory properties. Inorganic complexes, particularly those incorporating transition metals, demonstrated promising activity that may be attributed to their ability to interact with bimolecular targets and modulate cellular pathways. Similarly, organic derivatives revealed bioactive features that merit further exploration. Collectively, the results underscore the therapeutic potential of synthesized compounds and contribute to the growing field of drug design involving both inorganic and organic frameworks. This work emphasizes the integration of synthetic chemistry, as well as natural products with biological evaluation as a pathway toward identifying effective molecules with clinical relevance. Here, we highlighted some of the most recently developed Au(I/III), Pt(II/IV) and Ru(II/III) complexes that have shown significant in vivo antitumor properties between 2016 and 2025, as well as the antimicrobial and anti-inflammatory properties of different inorganic and organic compounds. Our review emphasizes on gold, platinum and ruthenium complexes synthesis and characterizations of inorganic and organic compounds with biomedical potential. The main focus is on the antitumor effects reported in 89 articles of inorganic and organic compounds, 53 on antimicrobial action and 17 on anti-inflammatory activities. In our review we cover the synthesis (30 articles) and characterizations (30 papers) of inorganic and organic compounds with potential biological and therapeutic effects. It is anticipated that this review will serve as a valuable resource in the future, particularly for professionals engaged in clinical, medical, and health-related disciplines.

Abstract: Photoactivatable nitric oxide donors (photoNORMs) are promising agents for con-trolled NO release and real-time optical tracking in biomedical theranostics. Here, we report a comprehensive density functional theory (DFT) and time-dependent DFT (TDDFT) study on a series of hybrid ruthenium–gold nanocluster systems of the gen-eral formula [(L)Ru(NO)(SH)@Au₂₀], where L = salen, bpb, porphyrin, or phthalocya-nine. Structural and bonding analyses reveal that the Ru–NO bond maintains a formal {RuNO}⁶ configuration with pronounced Ru→π*(NO) backbonding, leading to partial reduction of the NO ligand and an elongated N–O bond. NBO, NEDA, and ETS–NOCV analyses confirm that Ru–NO bonding is dominated by charge-transfer and polariza-tion components, while Ru–S and Au–S linkages exhibit delocalized, donor–acceptor character coupling the molecular chromophore with the metallic cluster. TDDFT re-sults reproduce visible–NIR absorption features arising from mixed metal-to-ligand and cluster-mediated charge-transfer transitions. The calculated zero–zero transition and reorganization energies predict NIR-II emission (1.8–3.8 μm), a region of high bi-omedical transparency, making these systems ideal candidates for luminescence-based NO sensing and therapy. This study establishes fundamental design principles for next-generation Ru-based photoNORMs integrated with plasmonic gold nanoclusters, highlighting their potential as multifunctional, optically trackable theranostic platforms.

Abstract: We report the synthesis, structural characterization, and ultrafast photophysical in-vestigation of a novel series of homoleptic and heteroleptic Zn(II) β-diketonates de-rived from donor–acceptor ligands. Single-crystal X-ray diffraction revealed that all complexes adopt monomeric octahedral geometries, with ancillary nitrogen-based ligands inducing variable distortions. UV–Vis absorption and femtosecond transient absorption spectroscopy established that the chelated β-diketonate ring constitutes the primary optically active chromophore, while Zn coordination markedly alters excit-ed-state dynamics. In contrast to the free ligand, which undergoes rapid internal con-version, Zn binding stabilizes the triplet state, generating a long-lived and chemically reactive species. Thermal and mass spectrometric analyses confirmed their stability and decomposition pathways, supporting their potential use as precursors for la-ser-induced three-dimensional ZnO growth. Such features underline the relevance of these complexes in photonic and electronic applications where controlled nanostruc-ture development is required. Overall, these findings provide fundamental insights into structure–photophysics relationships in Zn β-diketonates. They demonstrate how tailored ligand environments can be exploited to tune excited-state properties, offering a rational framework for the design of functional precursors suitable for nonlinear photolysis and advanced nanomaterial synthesis.

Abstract:

The oxygen deficient tungsten oxide W₁₈O₄₉ was synthesized through lattice oxygen escaping at high temperature in N₂ atmosphere. The temperature and inert atmosphere were critical conditions to initiate the lattice oxygen escaping to obtain W₁₈O₄₉. The synthesized tungsten oxides were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and ultraviolet-visible absorption spectroscope (UV-Vis). The composite gel was fabricated by the oxygen deficient tungsten oxide insertion into PVA-based gel, which was cross linked by glutaraldehyde. The gel was characterized by Fourier transform infrared (FTIR) spectroscopy and solar steam generation test. The result of the solar steam generation shows that the W₁₈O₄₉-PVA gel (steam generation rate 2.63 kg m^-2 h^-1) was faster than that of the pure PVA gel.

Abstract: Although spontaneous or complexation-induced reductions of Cu^II to Cu^I have occasionally been observed, controlling these processes remains a challenge. Herein, we report the synthesis of Cu^I complexes via the complexation-induced reduction of Cu^II complexes with pyridine-containing N₄ Schiff-base ligand L incorporating a biphenyl unit (L = N,N'-([1,1'-biphenyl]-2,2'-diyl)bis(1-(6-methylpyridin-2-yl)methanimine)). Such a reduction has not yet been observed in previously reported Cu^II complexes with pyridine-containing N₄ Schiff-base ligands, strongly suggesting that the torsional distortion of the ligand framework induced by the biphenyl moiety effectively promotes the complexation-induced reduction of Cu^II to Cu^I. The Cu^I complexes were thoroughly characterized by ¹H NMR spectroscopy, UV–vis–NIR spectroscopy, and single-crystal X-ray diffraction analyses. The [Cu^I(L)]⁺ complex undergoes a reversible redox process with its oxidized species, which was identified as a Cu^II complex based on spectroelectrochemical measurements and theoretical calculations.

Abstract: Two Nitrogen-modified mesoporous MCM-41 type silicas were synthesized by the sol-gel route and post-grafting surface modification procedure, obtaining an aminopropyl-modified MCM-41 (denoted MCM-41-N) and an aminoethyl-aminopropyl-modified MCM-41 (denoted MCM-41-NN). Hexavalent chromium removal from acidified water by adsorption and reduction to Cr(III) on the solid mesophases was analyzed. The modified silicas were characterized by powder X-ray diffraction, infrared spectroscopy, nitrogen adsorption-desorption measurements at -196 °C, X-ray photoelectron spectroscopy, 29Si solid state Nuclear Magnetic Resonance, and thermogravimetric analysis. Both samples exhibited very high capacities for decreasing Cr(VI) concentrations in water, according to the Langmuir isotherm model: 129.9 mg·g-1 for MCM-41-N and 133.3 mg·g-1for MCM-41-NN. The chromium speciation in the supernatant after 24 h indicates that MCM-41-N had a higher capacity to reduce Cr(VI) to the less toxic Cr(III) species than MCM-41-NN: 92.9 % vs 72.5 % when the initial Cr(VI) concentration was 10 ppm. These differences were related to the different capacity of nitrogen atoms in MCM-41-N and MCM-41-NN to interact with the surrounding surface silanols which are required for the chemical reduction of the hexavalent species to take place, as evidenced by infrared spectroscopy and X-ray photoelectron spectroscopy analysis. Also, the Cr(III)/Cr(VI) atomic ratios on the solid’s surfaces were higher for MCM-41-N. These results highlight the characteristics that nitrogen atoms incorporated to silica matrices must possess in order to maximize the transformation of Cr(VI) into the trivalent species, thereby reducing the generation of toxic waste harmful to living organisms.

Abstract: In recent years, researchers have made great efforts to develop effective semiconductor photocatalysts to harness the visible spectrum of sunlight in photocatalytic applications. Bismuth vanadate, BiVO4, has emerged as one of the most promising candidates for photocatalytic applications among few non-titania based visible light driven semiconductor photocatalysts. The BiVO4-based structures are intensively studied due to their exceptional ionic conductivity, photocatalytic behavior under ultra-violet and visible light, dielectric properties, ferroelastic and paraelastic phase transitions, and strong pigmentation. BiVO4 occurs in nature in three crystalline structures: orthorhombic pucherite, tetragonal dreyerite (tz), and monoclinic clinobisvanite (ms). All three crystal structures of BiVO4 are n-type semiconductors with corresponding energy gap values of 2.34, 2.40 and 2.90 eV, respectively. Different methods of synthesis have been reported for preparation of BiVO4 structures of varying morphologies and sizes. The morphology of BiVO4 is strongly influenced by the preparation method and reaction parameters. A comprehensive systematic study of developments, preparation methods, structure, different properties and advances in different applications over the past decade in research on BiVO4 based structure will be described. Finally, the current challenges and future outlook of the BiVO4 based structure will be highlighted, in the hope of contributing to guidelines for the future applications.

Abstract: Given the outstanding magnetic characteristics of lanthanide ions, the development of lanthanide complexes, transitioning from mononuclear to multinuclear, becomes imperative. Previous research utilized rhodamine Schiff base ligands to synthesize a series of mononuclear complexes exhibiting remarkable single-molecule magnetic properties alongside fluorescence characteristics. In the current study, we designed analogous ligands to synthesize complexes [Dy(HL1-o)(NO3)2(CH3OH)2]NO3·CH3OH (complex 1) and tetranuclear [Ln4(L1-c)2(L2)2(μ3-OH)2(NO3)2(CH3OH)4](NO3)2·2CH3CN·5CH3OH·2H2O (Ln = Dy, complex 2; Ln = Gd, complex 3), spanning from mononuclear to tetranuclear molecules. Magnetic susceptibility measurements show that 1 is a single-molecule magnet with Ueff = 33.2(10) K, 2 shows slow magnetic relaxation and 3 is a magnetic cooling material with the magnetic entropy change of 9.81 J kg−1 K−1 at 2 K and 5 T.

Abstract: Searching for new and efficient transfer hydrogenation catalysts, a series of new organometallic ruthenium(II)-arene complexes of the formulae [Ru(η6-p-cymene)(L)Cl][PF6] (1–8) and [Ru(η6-p-cymene)(L)Cl][Ru(η6-p-cymene)Cl3] (9–11) were synthesized and fully characterized. These were prepared from the reaction of pyridine-quinoline and biquinoline-based ligands (L) with [Ru(η6-p-cymene)(μ-Cl)Cl]2, in 1:2 and 1:1, metal (M) to ligand (L) molar ratios. Characterization includes a combination of spectroscopic methods (FT-IR, UV-Vis, multi nuclear NMR), elemental analysis and single-crystal X-ray crystallography. The pyridine-quinoline organic entities encountered, were prepared in high yield either via the thermal decarboxylation of the carboxylic acid congeners, namely 2,2′-pyridyl-quinoline-4-carboxylic acid (pqca), 8-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8-Mepqca), 6′-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (6′-Mepqca) and 8,6′-dimethyl-2,2′-pyridyl- quinoline-4-carboxylic acid (8,6′-Me2pqca), affording the desired ligands pq, 8-Mepq, 6′-Mepq and 8,6′-Me2pq, or by the classical Friedländer condensation, to yield 4,6′-dimethyl-2,2′-pyridyl-quinoline (4,6΄-Me2pq) and 4-methyl-2,2′-pyridyl-quinoline (4-Mepq) respectively. The solid-state structures of complexes 1–4, 6, 8 and 9 were determined showing a distorted octahedral coordination geometry. The unit cell of 3 contains two independent molecules (Ru-3), (Ru′-3) in a 1:1 ratio, due to a slight rotation of the arene ring. All complexes catalyze the transfer hydrogenation of acetophenone, using 2-propanol as a hydrogen donor in the presence of KΟiPr. Among them, complexes 1 and 5 bearing methyl groups at the 8 and 4 position of the quinoline moiety, convert acetophenone to 1-phenylethanol quantitatively, within approximately 10 minutes with final TOFs of 1600 h–1. The catalytic performance of complexes 1–11, towards the transfer hydrogenation of p-substituted acetophenone derivatives and benzophenone, ranges from moderate to excellent. An inner-sphere mechanism has been suggested based on the detection of ruthenium(II) hydride species.

Abstract: Antimicrobial resistance poses a growing threat to effective infection treatment, while imbalances in ascorbic acid (AA) levels are linked to various health issues. Nanotechnology offers innovative solutions, with carbon dot-based nanocomposites emerging as promising materials for both antimicrobial applications and sensitive detection of biomolecules. This study aimed to synthesize nitrogen-doped carbon dots (NCDs), copper oxide nanoparticles (CuO NPs), and their nanocomposites (CuO-NCDs), and to evaluate their electrochemical sensing of AA and antimicrobial activity. NCDs were prepared via pyrolysis of citric acid and urea, and CuO NPs by precipitation of copper nitrate. Characterization by UV-Vis, FT-IR, XRD, and SEM confirmed their optical properties, functional groups, crystallinity, and morphology. The CuO-NCD nanocomposite exhibited enhanced optical absorption with a reduced energy band gap (2.6 eV) compared to individual components. Electrochemical tests revealed a detection limit of 2.56 μM for AA and increased electrode surface area, indicating improved sensitivity and selectivity. Antimicrobial assays showed significant activity against Staphylococcus aureus, with a 24 mm inhibition zone at 200 mg/mL after 24 hours. These results demonstrate that CuO-NCD nanocomposites hold potential as dual-function materials for effective AA detection and combating microbial infections.

Abstract: The presence of impurities such as Ca, Mg and Al directly affects the purity of rare earth products precipitated by ammonium bicarbonate (ABC). Therefore, precipitation method and optimum conditions are the key to improving the separation efficiency of rare earths (REs) from impurities. In this paper, rare earth chloride (RECl3) was precipitated by ABC solution, and the co-precipitation rules and separation efficiency of Al, Fe, Ca and Mg ions from REs were investigated with or without the addition of triammonium citrate (TAC). The results show that as long as the REs precipitation percentage of RECl3 is controlled below 94%s, Ca and Mg ions will not enter the precipitate from their solution only containing them, and the purity of rare earth oxide (RE2O3) is up to 100%. However, the presence of Al and Fe impurities can lower the separation efficiency of REs from Ca and Mg. To obtain high purity of RE2O3, it is necessary to separate Al and Fe in advance. Firstly, Fe is precipitated and filtered 100% by adjusting pH to 4.12. Then, 90% of Al is precipitated only with 6% loss percentage of REs when adjusting pH at 4.6. When REs are precipitated at pH=6.43, the purity of the obtained RE2O3 is 97.83% with 1.05% Al and 0.21% Mg, without Ca and Fe. Which proves that Al has not been completely removed and party of Mg still enters the product. When REs are precipitated 60% by fractional precipitation method after removing Al and Fe, the purity of the obtained RE2O3 is 98.83% with 0.73% of Al and 0.06% of Mg. Furthermore, a small amount of TAC can assist the completely removing of Al, letting Ca and Mg remaining in solution until the rare earth precipitation percentage up to 99%. The purity of RE2O3 is 99.66% with only 0.09% of Al at the 94% precipitation percentage of REs. With a continuous precipitation crystallization method, the purity of RE2O3 reaches 99.87% with only 0.03% of Al.

Abstract: Phenylene-based bis-oxamate polydentate ligands offer unique opportunities for creating a large variety of coordination compounds in which paramagnetic metal ions are strongly magnetically coupled. The employment of iminonitroxyl (IN) radicals as supplementary ligands confers numerous benefits, including the strong ferromagnetic interaction between Ni and IN. Furthermore, the chelating IN can function as a blocking ligand, thereby impeding the formation of coordination polymers. In this study, we present the molecular, crystal structure, experimental, and theoretical magnetic behavior of an exceptional neutral trinuclear complex [Ni(L3−)2(IN)3]∙5MeOH (1) with a cyclic triangular arrangement. Moreover, in this compound three Ni2+ ions are linked by the two bis-oxamate ligands playing rare tritopic function due to an unprecedented triple deprotonation of the related meta-phenylene-bis(oxamic acid). Despite the presence of six possible magnetic couplings in the three-nuclear cluster 1, its behavior was reproduced well using a three-J model and ZFS, under the assumption that the three different Ni-IN interactions are equal to each other, whereas only two equivalent in value Ni-Ni interactions are taken into account, and the third one was equated to zero. These studies indicate the presence of two opposite in nature type of magnetic interactions within triangular core. DFT and CASSCF/NEVPT2 calculations were completed to support the experimental magnetic data simulation.

Abstract: The traditional preparation process of fluozirconic acid is carried out in a reaction kettle, where zirconium oxide reacts with concentrated hot hydrofluoric acid. However, the use of concentrated hot hydrofluoric acid leads to high process and equipment costs, severe environmental pollution, significant safety hazards. Moreover, the purity of the original solution after dissolution is low, and the phase composition is complex. In this paper, a preparation method for fluozirconic acid solution with controllable phase composition is studied. This is a dissolution method that using 99.8% purity sponge zirconium and 8N purity hydrofluoric acid of medium concentration as raw materials under normal temperature and pressure. The optimal dissolution process was determined experimentally as a hydrofluoric acid concentration of 35% and a liquid-solid ratio of 5 mL·g⁻¹. Under these conditions, the HZrF₅ phase content in the solution reached its maximum, thereby creating favorable conditions for the subsequent hydrometallurgical preparation of high purity zirconium tetrafluoride (ZrF₄), creating conditions for the subsequent preparation of high purity zirconium tetrafluoride through hydrometallurgy. At the same time, this paper also conducts certain explorations on the phase characterization of the solution.

Abstract: In this work, two series of isostructural Au(III) and Pt(II) alkynylphosphonium complexes [M(CNC)(C2−L−P(CH3)Ph2)]n+ Pt1–Pt3 (n = 0) and Au1–Au3 (n = 1), (CNC = 2,6-diphenylpyridine; L = phenyl, M1; biphenyl, M2; naphthyl, M3) were synthesized and characterized to discover the similarities and differences in photophysical properties between isoelectronic metallocenters. It is shown, that Au(III) and Pt(II) complexes obtained demonstrate different photophysical properties despite isoelectronic metal centres, and some reasons for that are discussed based on experimental data and quantum-chemical calculation results. Complex Pt1 also demonstrated the first example of room-temperature solution phosphorescence in the family of [Pt(CNC)(alkynyl)] complexes. It has been found that the crystal packing of Pt1 contains a Pt–H interaction, qualified by quantum-chemical calculations as unique hydrogen bond.

Abstract: The reaction of the bulky ligand 1,2-bis-(di-tert-butylphosphinomethyl)benzene,1 with [Ni(DME)Cl₂], 3, DME = 1,2-dimethoxyethane, at room temperature over extended periods, affords the new blue Zwitterionic complex [(1,2-C₆H₄-CH₂P^tBu₂-2-C₆H₄-CH₂P(H)^tBu₂)₂NiCl₃], 4, which contains a phosphonium group and an anionic nickel trichloride. This complex decomposes in alcohols such as methanol and the solution turn yellow. A discussion of the possible mechanism leading to the observed product is presented. Key to this is identification of the source of the phosphonium proton, which we speculated to arise from trace water in the initial nickel complex. To prove that trace water was present in [Ni(DME)Cl₂] a sample of this precursor was reacted under similar condition with anhydrous DMF alone. In addition to the known complex [Ni(DMF)₆)]²⁺[NiCl₄]^2-, 5, we identified the trans-diaqua complex [Ni(Cl)₂(H₂O)₂(DMF)₂], 6, which proved the presence of trace water. Interestingly in dimethylformamide [(1,2-C₆H₄-CH₂P^tBu₂-2-C₆H₄-CH₂P(H)^tBu₂)₂NiCl₃] exhibits thermochromic properties: an ambient temperature pale blue solution changes colour reversibly to yellow on cooling. This behaviour is specific to DMF and is related to the solvato-chromic behaviour exhibited by related DMF nickel complexes. A discussion of the NMR spectra of compound 4 in a range of solvents is presented. The structures of the previously prepared molybdenum complex, [1,2-(C₆H₄-CH₂P^tBu₂)₂Mo(CO)₄] and the bis-(phosphine sulfide) of the ligand, [1,2-(C₆H₄-H₂P(S)^tBu₂)₂], 5, are described for structural comparative purposes.

Abstract: The crystal-chemical behavior of two layered titanosilicate minerals with porous crystal structures: kupletskite, K2NaMn72+Ti2(Si4O12)2O2(OH)4F, and kupletskite-(Cs), Cs2NaMn72+Ti2(Si4O12)2O2(OH)4F, was investigated under high-temperature conditions using single-crystal and powder X-ray diffraction; infrared, optical absorption and Mössbauer spectroscopy and electron-microprobe analysis. Both minerals undergo topotactic transformation to dehydroxylated and oxidized high-temperature (HT) modifications at temperature above 500 °C while maintaining the basic bond topology of the astrophyllite structure-type. The high-temperature structures show contraction of the unit-cell parameters similar to that of Fe2+-dominant astrophyllite, indicating that Mn2+ oxidizes along with Fe2+. The oxidation of Mn2+ is confirmed by the increase of the Mn3+-related absorption (in optical spectra) that is inversely correlated with the intensity of O‒H bands in the infrared spectra. The Fe,Mn-oxidation is also evident by the contraction of the M(2), M(3) and M(4)O6 octahedra. The M(1)‒O bond length increases slightly, indicating a preference for mono- and divalent cations to occupy the M(1) site in the heated structure; this may be due to site-selective oxidation and/or migration of unoxidized cations (as previously shown for lobanovite) to this site. The role of extra framework A-site cations (K, Cs) in thermal expansion of these minerals is discussed.

Abstract: Partial reduction of transition metal oxides via defect engineering is a promising strategy to enhance their electronic and photocatalytic properties. In this study, we systematically explore the mechanochemical reduction of Nb2O5 using LiBH4 and NaBH4 as reducing agents. Electron paramagnetic resonance (EPR) spectroscopy confirms a successful partial reduction of the oxide, as seen by the presence of unpaired electrons. Interestingly, larger hydride concentrations do not necessarily enable a higher degree of reduction as large amounts of the boron hydrides act as a buffer material and thus hinder the effective transfer of mechanical energy. Powder X-ray diffraction (PXRD) and 7Li solid-state NMR spectroscopy indicate the intercalation of Li+ into the Nb2O5 lattice. Raman spectroscopy further reveals the increased structural disorder, while optical measurements show a decreased band gap compared to pristine Nb2O5. The partially reduced samples show significantly enhanced photocatalytic performance for methylene blue degradation relative to the unmodified oxides.