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Terahertz (THz) radiation has gained attention due to technological advancements, but its biological effects remain unclear. We investigated the impact of 2.3 THz radiation on SK-MEL-28 cells using metabolomic and gene network analysis. Forty metabolites, primarily related to purine, pyrimidine synthesis and breakdown pathways, were significantly altered post-irradiation. Lipids, such as ceramides and phosphatidylcholines, were also affected. Gene network reconstruction and analysis identified key regulators of the enzymes involved in biosynthesis and degradation of significantly altered metabolites. Mitochondrial membrane components, such as the respiratory chain complex, the proton-transporting ATP synthase complex, and components of lipid rafts reacted to THz radiation. We propose that THz radiation induces reversible disruption of the lipid raft macromolecular structure, thereby altering mitochondrial molecule transport while maintaining protein integrity, which explains the high cell survival rate. Our findings enhance the understanding of THz biological effects and emphasize the role of membrane components in the cellular response to THz radiation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

Zr-monosubstituted polyoxometalates (Zr-POMs) of the Lindqvist (Bu 4 N) 6 [{W 5 O 18 Zr(μ-OH)} 2 ] ( 1 ), Keggin (Bu 4 N) 8 [{PW 11 O 39 Zr(μ-OH)} 2 ] ( 2 ), and Wells-Dawson (Bu 4 N) 11.3 K 2.5 H 0.2 [{P 2 W 17 O 61 Zr} 2 (μ-OH) 2 ] ( 3 ) structures catalyze oxidation of alcohols using aqueous hydrogen peroxide as an oxidant. With 1 equiv of H 2 O 2 and 1 mol % of Zr-POM, selectivity toward aldehydes and ketones varied from good to excellent, depending on the alcohol nature. Catalytic activity and attainable substrate conversions strongly depended on the Zr-POM structure and most often decreased in the order 1 > 2 ≫ 3 . The reaction mechanism was probed using a test substrate, cyclobutanol, radical and 1 O 2 scavengers, and kinetic and spectroscopic (attenuated total reflectance-Fourier transform infrared (ATR-FT-IR), 31 P NMR and electrospray ionization-mass spectrometry (ESI-MS)) tools. The results point to heterolytic alcohol oxidation in the presence of 1 and 2 and homolytic alcohol oxidation in the presence of 3 . Kinetic and spectroscopic studies implicated an oxidation mechanism that involves both alcohol and peroxide binding to 2 followed by an inner-sphere heterolytic H-abstraction from the α-C-H bond by the Zr-hydroperoxo group, leading to a carbonyl compound. The unique capability of 1 to generate 1 O 2 upon interaction with H 2 O 2 complicates the reaction kinetics and improves the product yield. Spectroscopic studies coupled with stoichiometric experiments unveiled that dimeric monoperoxo {Zr 2 (μ-η 2 :η 2 -O 2 )} and monomeric hydroperoxo {Zr(η 2 -OOH)} species accomplish the transformation of alcohols to carbonyl compounds.

The Zr-monosubstituted Keggin-type dimeric phosphotungstate (Bu 4 N) 8 [{PW 11 O 39 Zr(μ-OH)(H 2 O)} 2 ] ( 1 ) efficiently catalyzes epoxidation of C═C bonds in various kinds of alkenes, including terminal ones, with aqueous H 2 O 2 as oxidant. Less sterically hindered double bonds are preferably epoxidized despite their lower nucleophilicity. Basic additives (Bu 4 NOH) in the amount of 1 equiv per dimer 1 suppress H 2 O 2 unproductive decomposition, increase substrate conversion, improve yield of heterolytic oxidation products and oxidant utilization efficiency, and also affect regioselectivity of epoxidation, enhancing oxygen transfer to sterically hindered electron-rich C═C bonds. Acid additives produce a reverse effect on the substrate conversion and H 2 O 2 efficiency. The reaction mechanism was explored using a range of test substrates, kinetic, and spectroscopic tools. The opposite effects of acid and base additives on alkene epoxidation and H 2 O 2 degradation have been rationalized in terms of their impact on hydrolysis of 1 to form monomeric species, [PW 11 O 39 Zr(OH)(H 2 O) x ] 4- ( 1-M , x = 1 or 2), which favors H 2 O 2 homolytic decomposition. The interaction of 1 with H 2 O 2 has been investigated by HR-ESI-MS, ATR-FT-IR, and 31 P NMR spectroscopic techniques. The combination of spectroscopic studies and kinetic modeling implicated the existence of two types of dimeric peroxo complexes, [Zr 2 (μ-η 2 :η 2 -O 2 ){PW 11 O 39 } 2 (H 2 O) x ]] 8- and [{Zr(μ-η 2 -O 2 )} 2 (PW 11 O 39 ) 2 (H 2 O) y ] 10- , along with monomeric Zr (hydro)peroxo species that begin to dominate at a high excess of H 2 O 2 . Both dimeric μ-η 2 -peroxo intermediates are inert toward alkenes under stoichiometric conditions. V-shape Hammett plots obtained for epoxidation of p -substituted styrenes suggested a biphilic nature of the active oxidizing species, which are monomeric Zr-hydroperoxo and peroxo species. Small basic additives increase the electrophilicity of the catalyst and decrease its nucleophilicity. HR-ESI-MS has identified a dimeric, most likely, bridging hydroperoxo species [{PW 11 O 39 Zr} 2 (μ-O)(μ-OOH)] 9- , which may account for the improved epoxidation selectivity and regioselectivity toward sterically hindered C═C bonds.

The decomposition of hydrogen peroxide (H 2 O 2 ) is the main undesired side reaction in catalytic oxidation processes of industrial interest that make use of H 2 O 2 as a terminal oxidant, such as the epoxidation of alkenes. However, the mechanism responsible for this reaction is still poorly understood, thus hindering the development of design rules to maximize the efficiency of catalytic oxidations in terms of product selectivity and oxidant utilization efficiency. Here, we thoroughly investigated the H 2 O 2 decomposition mechanism using a Zr-monosubstituted dimeric Lindqvist tungstate, (Bu 4 N) 6 [{W 5 O 18 Zr(μ-OH)} 2 ] ( {ZrW 5 } 2 ), which revealed high activity for this reaction in acetonitrile. The mechanism of the {ZrW 5 } 2 -catalyzed H 2 O 2 degradation in the absence of an organic substrate was investigated using kinetic, spectroscopic, and computational tools. The reaction is first order in the Zr catalyst and shows saturation behavior with increasing H 2 O 2 concentration. The apparent activation energy is 11.5 kcal·mol -1 , which is significantly lower than the values previously found for Ti- and Nb-substituted Lindqvist tungstates (14.6 and 16.7 kcal·mol -1 , respectively). EPR spectroscopic studies indicated the formation of superoxide radicals, while EPR with a specific singlet oxygen trap, 2,2,6,6-tetramethylpiperidone (4-oxo-TEMP), revealed the generation of 1 O 2 . The interaction of test substrates, α-terpinene and tetramethylethylene, with H 2 O 2 in the presence of {ZrW 5 } 2 corroborated the formation of products typical of the oxidation processes that engage 1 O 2 (endoperoxide ascaridole and 2,3-dimethyl-3-butene-2-hydroperoxide, respectively). While radical scavengers t BuOH and p -benzoquinone produced no effect on the peroxide product yield, the addition of 4-oxo-TEMP significantly reduced it. After optimization of the reaction conditions, a 90% yield of ascaridole was attained. DFT calculations provided an atomistic description of the H 2 O 2 decomposition mechanism by Zr-substituted Lindqvist tungstate catalysts. Calculations showed that the reaction proceeds through a Zr-trioxidane [Zr-η 2 -OO(OH)] key intermediate, whose formation is the rate-determining step. The Zr-substituted POM activates heterolytically a first H 2 O 2 molecule to generate a Zr-peroxo species, which attacks nucleophilically to a second H 2 O 2 , causing its heterolytic O-O cleavage to yield the Zr-trioxidane complex. In agreement with spectroscopic and kinetic studies, the lowest-energy pathway involves dimeric Zr species and an inner-sphere mechanism. Still, we also found monomeric inner- and outer-sphere pathways that are close in energy and could coexist with the dimeric one. The highly reactive Zr-trioxidane intermediate can evolve heterolytically to release singlet oxygen and also decompose homolytically, producing superoxide as the predominant radical species. For H 2 O 2 decomposition by Ti- and Nb-substituted POMs, we also propose the formation of the TM-trioxidane key intermediate, finding good agreement with the observed trends in apparent activation energies., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Probes sensitive to mechanical stress are in demand for the analysis of pressure distribution in materials, and the design of pressure sensors based on metal-organic frameworks (MOFs) is highly promising due to their structural tunability. We report a new pressure-sensing material, which is based on the UiO-66 framework with trace amounts of a spin probe (0.03 wt%) encapsulated in cavities. To obtain this material, we developed an approach for encapsulation of stable nitroxide radical TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl) into the micropores of UiO-66 during its solvothermal synthesis. Pressure read-out using electron paramagnetic resonance (EPR) spectroscopy allows monitoring the degradation of the defected MOF structure upon pressurization, where full collapse of pores occurs at as low a pressure as 0.13 GPa. The developed methodology can be used in and ex situ and provides sensitive tools for non-destructive mapping of pressure effects in various materials.

The catalytic performance of Zr-abtc and MIP-200 metal-organic frameworks consisting of 8-connected Zr 6 clusters and tetratopic linkers was investigated in H 2 O 2 -based selective oxidations and compared with that of 12-coordinated UiO-66 and UiO-67. Zr-abtc demonstrated advantages in both substrate conversion and product selectivity for epoxidation of electron-deficient C=C bonds in α,β-unsaturated ketones. The significant predominance of 1,2-epoxide in carvone epoxidation, coupled with high sulfone selectivity in thioether oxidation, points to a nucleophilic oxidation mechanism over Zr-abtc. The superior catalytic performance in the epoxidation of unsaturated ketones correlates with a larger amount of weak basic sites in Zr-abtc. Electrophilic activation of H 2 O 2 can also be realized, as evidenced by the high activity of Zr-abtc in epoxidation of the electron-rich C=C bond in caryophyllene. XRD and FTIR studies confirmed the retention of the Zr-abtc structure after the catalysis. The low activity of MIP-200 in H 2 O 2 -based oxidations is most likely related to its specific hydrophilicity, which disfavors adsorption of organic substrates and H 2 O 2 ., (© 2021 Wiley-VCH GmbH.)

Zr-based metal-organic frameworks (Zr-MOF) UiO-66 and UiO-67 catalyze thioether oxidation in nonprotic solvents with unprecedentedly high selectivity toward corresponding sulfones (96-99% at ca. 50% sulfide conversion with only 1 equiv of H 2 O 2 ). The reaction mechanism has been investigated using test substrates, kinetic, adsorption, isotopic ( 18 O) labeling, and spectroscopic tools. The following facts point out a nucleophilic character of the peroxo species responsible for the superior formation of sulfones: (1) nucleophilic parameter X Nu = 0.92 in the oxidation of thianthrene 5-oxide and its decrease upon addition of acid; (2) sulfone to sulfoxide ratio of 24 in the competitive oxidation of methyl phenyl sulfoxide and p -Br-methyl phenyl sulfide; (3) significantly lower initial rates of methyl phenyl sulfide oxidation relative to methyl phenyl sulfoxide ( k S / k SO = 0.05); and (4) positive slope ρ = +0.42 of the Hammett plot for competitive oxidation of p -substituted aryl methyl sulfoxides. Nucleophilic activation of H 2 O 2 on Zr-MOF is also manifested by their capability of catalyzing epoxidation of electron-deficient C═C bonds in α,β-unsaturated ketones accompanied by oxidation of acetonitrile solvent. Kinetic modeling on methyl phenyl sulfoxide oxidation coupled with adsorption studies supports a mechanism that involves the interaction of H 2 O 2 with Zr sites with the formation of a nucleophilic oxidizing species and release of water followed by oxygen atom transfer from the nucleophilic oxidant to sulfoxide that competes with water for Zr sites. The nucleophilic peroxo species coexists with an electrophilic one, ZrOOH, capable of oxygen atom transfer to nucleophilic sulfides. The predominance of nucleophilic activation of H 2 O 2 over electrophilic one is, most likely, ensured by the presence of weak basic sites in Zr-MOFs identified by FTIR spectroscopy of adsorbed CDCl 3 and quantified by adsorption of isobutyric acid.