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The Faraday efficiency of CO 2 electroreduction to CO catalyzed by metalloporphyrins (MTPP, M = Fe, Co, Cu, Zn and Ni) is linearly related to the reaction energy barrier of the first proton-coupled electron reduction. [Display omitted] • Five metalloporphyrins(MTPPs) with different metal centers are compared for CO 2 RR. • CO 2 RR mechanism on MTPPs are calculated by first-principles calculations. • CoTPP exhibits the best CO 2 RR activity and selectivity. • The results of theoretical calculation are well verified by experimental tests. • The linear correlation between the selectivity of CO and the key energy barrier is revealed. Metal-functionalized porphyrin-like graphene structures are promising electrocatalysts for carbon dioxide reduction reaction (CO 2 RR) as their metal centers can modulate activity. Yet, the role of metal center of metalloporphyrins (MTPPs) in CO 2 reaction activity is still lacking deep understanding. Here, CO 2 RR mechanism on MTPPs with five different metal centers (M = Fe, Co, Cu, Zn and Ni) are examined by first-principles calculations. The *COOH formation is the rate determined step on the five MTPP structures, and the CoTPP exhibits the best CO 2 RR activity while ZnTPP and NiTPP are the worst, which is also verified by our experiment. The CO 2 RR activity is controlled by adsorption states of intermediates (*CO, *COOH), i.e., chemisorption (e.g., on CoTPP) and physisorption (on ZnTPP and NiTPP) of intermediates will lead to good and poor activity, respectively. The deeper the d- band center of the porphyrin ring complexed metal atom, the weaker bonding of MTPP with CO and COOH. Theoretical calculations and experimental results indicate that MTPPs with Co and Fe centers lead to a reduction in the energy barriers for the two uphill reaction steps in the electrocatalytic CO 2 reduction process, thereby enhancing CO 2 reduction electrocatalytic activity. Faradaic efficiency of CO is correlated with the reaction energy barrier of the first proton-coupled electron reduction process, displaying a strong linear correlation. This work provides a fundamental understanding of MTPPs used as electrocatalysts for CO 2 RR. [ABSTRACT FROM AUTHOR]

Cationic Mn(III)‐meso‐tetraarylporphyrin derivatives, substituted in para position with different size alkyl chains, were investigated to function as antioxidants in free‐radical degradation of high‐molar‐mass hyaluronan by the methods of rotational viscometry and oximetry. The results of rotational viscometry showed that MnTM‐4‐PyP5+, MnTE‐4‐PyP5+, MnTPr‐4‐PyP5+, MnTPen‐4‐PyP5+ and MnTHep‐4‐PyP5+ showed high efficiency in decomposing H2O2, and reducing of peroxidized hyaluronan. When using oxygen electrode, MnTE‐4‐PyP5+, MnTPr‐4‐PyP5+, MnTPen‐4‐PyP5+, and MnTHep‐4‐PyP5+ applied to function as protective antioxidants in hyaluronan degradation, the uptake of dissolved oxygen from the reaction milieu was rapid, followed by continual increase in oxygen concentration up to the end of the measurement. However, when especially MnTE‐4‐PyP5+, MnTPr‐4‐PyP5+, and MnTPen‐4‐PyP5+ were examined as hyaluronan chain‐breaking antioxidants, after short‐term dissolved oxygen uptake, almost no increase in oxygen concentration was shown. [ABSTRACT FROM AUTHOR]

Single atom alloy AgCu catalysts have attracted great attention, since doping the single Cu atom introduces narrow free-atom-like Cu 3d states in the electronic structure. These peculiar electronic states can reduce the activation energies in some reactions and offer valuable guidelines for improving catalytic performance. However, the geometric tuning effect of single Cu atoms in Ag catalysts and the structure–activity relationship of AgCu catalysts remain unclear. Here, we prepared well-resolved pristine Agn− as well as single atom alloy Agn−1Cu− and Agn−1Au− (n = 7–20) clusters and investigated their reactivity with O2. We found that replacing an Ag atom in Agn− (n = 15–18) with a Cu atom significantly increases the reactivity with O2, while replacement of an Ag with an Au atom has negligible effects. The adsorption of O2 on Agn− or Agn−1Cu− clusters follows the single electron transfer mechanism, in which the cluster activity is dependent on two descriptors, the energy level of α-HOMO (strong correlation) and the α-HOMO–LUMO gap (weak correlation). Our calculation demonstrated that the cluster arrangements caused by single Cu atom alloying would affect the above activity descriptors and, therefore, regulates clusters' chemical activity. In addition, the observed reactivity of clusters in the representative sizes with n = 17–19 can also be interpreted using the symmetry-adapted orbital model. Our work provides meaningful information to understand the chemical activities of related single-atom-alloy catalysts. [ABSTRACT FROM AUTHOR]

n‐Bu4NI/K2S2O8 mediated C−N coupling between aldehydes and amides is reported. A strong electronic effect is observed on the aromatic aldehyde substrates. The transformylation from aldehyde to amide takes place exclusively when an aromatic aldehyde bears electron‐donating groups at either the ortho or para position of the formyl group, while the cross‐dehydrogenative coupling dominates in the absence of these groups. Both the density functional theory (DFT) thermochemistry calculations and experimental data support the proposed single electron transfer mechanism with the formation of an acyl radical intermediate in the cross‐dehydrogenative coupling. The n‐Bu4NI/K2S2O8 mediated oxidative cyclization between 2‐aminobenzamide and aldehydes is also reported, with four quinazolin‐4(3H)‐ones prepared in 65–99 % yields. [ABSTRACT FROM AUTHOR]

The structure and electronic properties of a molecule at an electrochemical interface are changed by interactions with the electrode surface and the electrolyte solution, which can be significantly modulated by an applied voltage. We present an efficient self-consistent quantum mechanics/molecular mechanics (QM/MM) approach to study a physisorbed molecule at a metal electrode–electrolyte interface under the constant-voltage condition. The approach employs a classical polarizable double electrode model, which enables us to study the QM/MM system in the constant-voltage ensemble. A mean-field embedding approximation is further introduced in order to overcome the difficulties associated with statistical sampling of the electrolyte configurations. The results of applying the method to a test system indicate that the adsorbed molecule is no less or slightly more polarized at the interface than in the bulk electrolyte solution. The geometry of the horizontally adsorbed molecule is modulated by their electrostatic interactions with the polarizable electrode surfaces and also the interactions with cations attracted toward the interface when the adsorbate is reduced. We also demonstrate that the approach can be used to quantitatively evaluate the reorganization energy of a one electron reduction reaction of a molecule in an electrochemical cell. [ABSTRACT FROM AUTHOR]

Reaction of the 1,2‐disilylenes {(DipArAm)Si}2 (DipArAm=[(NDip)2CAr]−, Dip=2,6‐diisopropylphenyl, Ar=4‐C6H4But (Ar') 1 a or Ph 1 b) and two abnormal N‐heterocyclic silylenes, (DipArAm)SiOCSi{(NDip)2CAr} (Ar=Ar' 3 a or Ph 3 b) with N2O led to formation of unprecedented examples of uncoordinated silicon analogues of carboxylic acid anhydrides, (DipArAm)(O=)SiOSi(=O)(DipArAm) (Ar=Ar' 2 a or Ph 2 b). Both compounds have been fully characterized, and the mechanism of formation of one explored using DFT calculations. Reduction of sila‐acid anhydride 2 a with a dimagnesium(I) compound, [{(MesNacnac)Mg}2] (MesNacnac=[(MesNCMe)2CH]−, Mes=mesityl), led to the one‐electron reduction of the anhydride and formation of a magnesium complex of a sila‐acid anhydride radical anion [(MesNacnac)Mg{(OSi(DipAr'Am)}2O] 5. A combination of EPR spectroscopic studies and DFT calculations reveal the unpaired electron to largely reside on one of the amidinate ligands of the complex. [ABSTRACT FROM AUTHOR]

Reported herein is an efficient and eco-friendly peri-selective monohydroxylation of naphthalene monoimides (NMIs) to access 4-hydroxy NMIs, which possess multidisciplinary applications. The key aspect of this method is the utilization of cobalt(II)-catalysis via a single electron transfer mechanism to achieve site-selective C(sp2)-hydroxylation. Transformation of the hydroxyl group into pseudohalides reveals its applications towards cross-coupling reactions. [ABSTRACT FROM AUTHOR]

This study sought to optimize the ultrasonic-assisted extraction of polyphenolic compounds from unmature Ajwa date seeds (UMS), conduct untargeted metabolite identification and assess antioxidant and depigmenting activities. Response surface methodology (RSM) utilizing the Box–Behnken design (BBD) and artificial neural network (ANN) modeling was applied to optimize extraction conditions, including the ethanol concentration, extraction temperature and time. The determined optimal conditions comprised the ethanol concentration (62.00%), extraction time (29.00 min), and extraction temperature (50 °C). Under these conditions, UMS exhibited total phenolic content (TPC) and total flavonoid content (TFC) values of 77.52 ± 1.55 mgGAE/g and 58.85 ± 1.12 mgCE/g, respectively, with low relative standard deviation (RSD%) and relative standard error (RSE%). High-resolution mass spectrometry analysis unveiled the presence of 104 secondary metabolites in UMS, encompassing phenols, flavonoids, sesquiterpenoids, lignans and fatty acids. Furthermore, UMS demonstrated robust antioxidant activities in various cell-free antioxidant assays, implicating engagement in both hydrogen atom transfer and single electron transfer mechanisms. Additionally, UMS effectively mitigated tert-butyl hydroperoxide (t-BHP)-induced cellular reactive oxygen species (ROS) generation in a concentration-dependent manner. Crucially, UMS showcased the ability to activate mitogen-activated protein kinases (MAPKs) and suppress key proteins including tyrosinase (Tyr), tyrosinase-related protein-1 and -2 (Trp-1 and -2) and microphthalmia-associated transcription factor (MITF), which associated melanin production in MNT-1 cell. In summary, this study not only optimized the extraction process for polyphenolic compounds from UMS but also elucidated its diverse secondary metabolite profile. The observed antioxidant and depigmenting activities underscore the promising applications of UMS in skincare formulations and pharmaceutical developments. [ABSTRACT FROM AUTHOR]

This paper explores the interaction of divalent [Sm(DippForm)2(thf)2] with substrates containing azo linkages. Treatment of [Sm(DippForm)2(thf)2] with trans‐azobenzene results in formation of mononuclear [Smlll(DippForm)2(Ph2N2)(thf)] ⋅ 3THF (1) or dinuclear [Smlll(DippForm)(Ph2N2)(thf)]2 ⋅ 4THF (2) and [Sm(DippForm)3] depending on the reaction stoichiometry, where azobenzene has undergone either a one or two electron reduction. These reactions parallel the corresponding reactions of [Sm(C5Me5)2(thf)2], but the coordination of [N2Ph2]− in 1 differs significantly from that of {Sm(C5Me5)2(Ph2N2)(thf)}. On the other hand, the structure of 2 is similar to that of the pentamethylcyclopentadienyl analogue. The reaction of [Sm(DippForm)2(thf)2] with 1H‐1,2,3‐benzotriazole also yielded a trivalent samarium complex containing benzotriazolate (btz), [Smlll(DippForm)2(btz)(thf)] ⋅ THF (3), and suggests more utilization of 1H‐1,2,3‐benzotriazole in divalent lanthanoid reduction chemistry is possible. [ABSTRACT FROM AUTHOR]

Photo‐induced electron transfer is a fundamental step in photochemical reactions, where light energy is used to drive chemical transformations. However, conventional outer‐sphere single electron transfer mechanisms encounter multiple limitations, notably requiring redox potential matching between photocatalysts and substrates, thereby impeding the activation of non‐activated carbon‐halogen bonds. In this concept review, we present an elucidation of the photophysical and photochemical properties exhibited by polynuclear gold photocatalysts, with a particular emphasis on their inner‐sphere single electron transfer mechanism. By exploring these intricate aspects, we endeavor to furnish readers with a more profound insight into the remarkable potential of polynuclear gold photocatalysts and the indispensable role played by inner‐sphere electron transfer in the realm of photocatalysis. [ABSTRACT FROM AUTHOR]

Five new Betti base copper(II) complexes (C1–C5) are successfully synthesized and characterized spectroscopically. X-ray diffraction analysis confirmed the square planar geometry of complex C4. Their catalytic application in the C–H functionalization of aromatic amines for azidation was successfully demonstrated under ultrasonication. Complex C5 showed better catalytic activity and produced 2-azidoaniline with a yield of 85%, which is higher than the existing methods; it also performed better than commercial catalysts, with a higher efficiency. The reaction involves a lower catalytic loading and a short reaction time. Control experiments were carried out to predict the reaction pathway. Based on the results, a plausible mechanism involving a free radical pathway accompanied by a single electron transfer mechanism is proposed. The substrate scope was also studied with different aromatic amines, and the corresponding azides were obtained successfully. All the synthesized azides were employed in click reactions to obtain the respective triazoles. The biological relevance of the triazoles was also explored successfully using molecular docking studies against SARS-CoV-2 main protease Omicron P132H. [ABSTRACT FROM AUTHOR]

The reduction of 4-nitrothiophenol (NTP) to 4-4′-dimercaptoazobenzene (DMAB) on laser illuminated noble metal nanoparticles is one of the most widely studied plasmon mediated reactions. The reaction is most likely triggered by a transfer of low energy electrons from the nanoparticle to the adsorbed molecules. Besides the formation of DMAB, dissociative side reactions of NTP have also been observed. Here, we present a crossed electron-molecular beam study of free electron attachment to isolated NTP in the gas-phase. Negative ion yields are recorded as a function of the electron energy, which helps to assess the accessibility of single electron reduction pathways after photon induced electron transfer from nanoparticles. The dominant process observed with isolated NTP is associative electron attachment leading to the formation of the parent anion of NTP. Dissociative electron attachment pathways could be revealed with much lower intensities, leading mainly to the loss of functional groups. The energy gained by one electron reduction of NTP may also enhance the desorption of NTP from nanoparticles. Our supporting experiments with small clusters, then, show that further reaction steps are necessary after electron attachment to produce DMAB on the surfaces. [ABSTRACT FROM AUTHOR]

Azo compounds are efficient electron acceptors. Upon one‐electron reduction they generally isomerize forming the thermodynamically most stable radical anion. Herein we show that the size of the central ring in 1,2‐diazocines and diazonines has a ruling influence on the configuration of the one‐electron reduced species. Markedly, diazonines, which bear a central nine membered heterocycle, show light‐induced E/Z isomerization, but retain the configuration of the diazene N=N moiety upon one‐electron reduction. Accordingly, E/Z isomerization is not induced by reduction. [ABSTRACT FROM AUTHOR]

Ferulic acid has numerous beneficial effects on human health, which are frequently attributed to its antioxidant behavior. In this report, many of them are reviewed, and 185 new ferulic acid derivatives are computationally designed using the CADMA-Chem protocol. Consequently, their chemical space was sampled and evaluated. To that purpose, selection and elimination scores were used, which are built from a set of descriptors accounting for ADME properties, toxicity, and synthetic accessibility. After the first screening, 12 derivatives were selected and further investigated. Their potential role as antioxidants was predicted from reactivity indexes directly related to the formal hydrogen atom transfer and the single electron transfer mechanisms. The best performing molecules were identified by comparisons with the parent molecule and two references: Trolox and α-tocopherol. Their potential as polygenic neuroprotectors was investigated through the interactions with enzymes directly related to the etiologies of Parkinson's and Alzheimer's diseases. These enzymes are acetylcholinesterase, catechol-O-methyltransferase, and monoamine oxidase B. Based on the obtained results, the most promising candidates (FA-26, FA-118, and FA-138) are proposed as multifunctional antioxidants with potential neuroprotective effects. The findings derived from this investigation are encouraging and might promote further investigations on these molecules. [ABSTRACT FROM AUTHOR]

During the oxidation of hydrocarbons using hydrogen peroxide solutions, the evolution of gaseous oxygen is a side and undesirable process, in which the consumption of the oxidizer is not associated with the formation of target products. Therefore, no attention is paid to the systematic study of the chemical composition of the gas and the mechanisms of its formation. Filling this gap, the authors discovered a number of new, previously unidentified, interesting facts concerning both gas evolution and the oxidation of hydrocarbons. In a 33% H2O2/Cu2Cl4·2DMG/CH3CN system, where DMG is dimethylglyoxime (Butane-2,3-dione dioxime), and is at 50 °C, evidence of significant evolution of gaseous hydrogen, along with the evolution of gaseous oxygen was found. In the authors' opinion, which requires additional verification, the ratio of gaseous hydrogen and oxygen in the discussed catalytic system can reach up to 1:1. The conditions in which only gaseous oxygen is formed are selected. Using a number of oxidizable hydrocarbons with the first adiabatic ionization potentials (AIPs) of a wide range of values, it was found that the first stage of such a process of evolving only gaseous oxygen was the single electron transfer from hydrogen peroxide molecules to trinuclear copper clusters with the formation, respectively, of hydrogen peroxide radical cations H2O2•+ and radical anions Cu3Cl5•− (AIP = 5 eV). When the conditions for the implementation of such a single electron transfer mechanism are exhausted, the channel of decomposition of hydrogen peroxide molecules into gaseous hydrogen and oxygen is switched on, which is accompanied by the transition of the system to an oscillatory mode of gas evolution. In some cases, the formation of additional amounts of gaseous products is provided by the catalytically activated decomposition of water molecules into hydrogen and oxygen after the complete consumption of hydrogen peroxide molecules in the reaction of gaseous oxygen evolution. The adiabatic electron affinity of various forms of copper molecules involved in chemical processes is calculated by the density functional theory method. [ABSTRACT FROM AUTHOR]

Storing uranium hexafluoride, UF6, is challenging due to the high chemical reactivity and volatility. Dissolution of UF6 into the ionic liquid reduces volatility while simultaneously providing stability for the dissolved species. The ionic liquid, 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide provides a stable, non-volatile environment for the reactive dissolution of UF6. The oxidation of the bis(trifluoromethylsulfonyl)imide anion (TFSI) to form a radical facilitates dissolution. Spectroscopic analysis indicates the dissolution occurs through the one electron reduction of UF6 to produce the pentavalent UF6− species. [ABSTRACT FROM AUTHOR]

Nitrogen reduction under mild conditions (room T and atmospheric P), using a non‐fossil source of hydrogen remains a challenge. Molecular metal complexes, notably Mo based, have recently been shown to be active for such nitrogen fixation. We report electrochemical N2 splitting with a MoIII triphosphino complex [(PPP)MoI3], at room temperature and a moderately negative potential. A MoIV nitride species was generated, which is confirmed by electrochemistry and NMR studies. The reaction goes through two successive one electron reductions of the starting Mo species, coordination of a N2 molecule, and further splitting to a MoIV nitride complex. Preliminary DFT studies support the formation of a bridging MoIN2MoI dinitrogen dimer evolving to the Mo nitride via a low energy transition state. This example joins a short list of molecular complexes for N2 electrochemical reductive cleavage. It opens a door to electrochemical proton‐coupled electron transfer (PCET) conversion studies of N2 to NH3. [ABSTRACT FROM AUTHOR]

• The effectiveness and feasibility of the CO 2 •− was evidenced. • The second-order rate constants of CO 2 •− (k C O 2 • − ″) with halogenated alkanes were firstly quantified. • k C O 2 • − ″ and E LUMO of chlorinated alkanes presented a linear negative correlation. • CO 2 •− followed a single electron transfer mechanism for CHCl 3 degradation. Carbon dioxide radical anion (CO 2 •−) recently becomes appreciated in halogenated contaminants elimination; nevertheless, its application has been restricted by insufficient mechanistic understanding. Herein, we provided a quantitative insight into the kinetics and mechanisms of CO 2 •− mediated dehalogenation of halogenated alkanes. A CO 2 •− dominated UV 254 /H 2 O 2 /HCOO− system has been successfully established and demonstrated for effective elimination of 7 kinds of halogenated alkanes (71.3 % to 100 % of removal). Using a laser flash photolysis technology, the second-order rate constants of CO 2 •− (k C O 2 • − ″) reacting with CCl 4 , CHCl 3 and CH 2 Cl 2 were firstly reported, to be 2.5 × 108, 6.2 × 107 and 5.8 × 106 M−1s−1, respectively. k C O 2 • − ″ presented a significant negative correlation with the lowest unoccupied molecular orbital energy (E LUMO) of chlorinated alkanes, proving that the enhanced dehalogenation of CO 2 •− was attributed by direct electron transfer mechanism. A fitting model was developed accordingly for k C O 2 • − ″ prediction. This study also demonstrated that the CO 2 •− mediated ARP effectively removed halogenated alkanes regardless of pH condition (6.0∼9.0) and bicarbonate concentrations. These findings are significant in advancing the scientific understanding of CO 2 •− mediated ARP. This reductive process a promising control strategy for halogenated contaminants, such as polyfluoroalkyl substances (PFAS) and halogenated pharmaceuticals. [Display omitted] [ABSTRACT FROM AUTHOR]

The article highlights that the industrial chemical, phenol has been deployed in applications in various fields including household products, nylon, polymers, and the manufacturing of other chemical derivatives. It also discusses that 12 million metric tons of phenol are produced each year, and greater than 90% of phenol is produced through the Hock process.

The C3-selective homodimerization of quinoxalinones is described. A C3-sp2 carbanion species generated through deprotonation of quinoxalinone using potassium tert-butoxide (KOtBu) transfers an electron (single electron transfer mechanism) to a second quinoxalinone, affording a radical–anion intermediate. The radical scavenging and electron paramagnetic resonance (EPR) experiments support the plausible radical reaction pathway. A mild reaction temperature and a short reaction time were attained under cost-effective conditions, which reveal the amenability of this protocol to pharmaceutical and chemical industries. [ABSTRACT FROM AUTHOR]

The voltammetric behaviour of Rhodamine B was studied at a screen-printed carbon electrode (SPCE), by cyclic and differential pulse voltammetry. Cyclic voltammograms exhibited two reduction peaks (designated R1 and R2) generated from the reduction of the parent compound through, first, one electron reduction (R1) to give a radical species, and then a further one-electron, one-proton reduction to give a neutral molecule (R2). On the reverse positive-going scan, two oxidation peaks were observed. The first, O1, resulted from the oxidation of the species generated at R2, and the second, O2, through the one-electron oxidation of the amine group. The nature of the redox reactions was further investigated by observing the effect of scan rate and pH on the voltammetric behaviour. The developed SPCE method was evaluated by carrying out Rhodamine B determinations on a spiked and unspiked environmental water sample. A mean recovery of 94.3% with an associated coefficient of variation of 2.9% was obtained. The performance characteristics indicated that reliable data may be obtained for Rhodamine B measurements in environmental water samples using this approach. [ABSTRACT FROM AUTHOR]

We propose a simple method to evaluate the triple quantum dots (TQDs) coupled in series with the compact device structure. Compact coupled quantum dots, each with an attached control gate, offer promising applications as quantum computing and single-electron transfer devices. However, device reduction required in practical applications creates a capacitive cross-talk between a control gate and its neighboring dots making it difficult to determine the charge transition boundaries in each dot. To properly evaluate the electron-transfer characteristics of TQDs, a method is proposed whereby the three gate voltages are simultaneously swept. We studied the charge stability diagram of the compact TQDs using Monte Carlo simulations, and confirmed the effectiveness of the method. Compact Si- TQDs were actually fabricated by the use of pattern-dependent oxidation and additional oxidation method for this study. The method was then applied to the stability diagrams obtained from the devices. The nine measurements of the gate capacitances between the three sets of dots and gates were reproduced, confirming the formation of the TQDs. [ABSTRACT FROM AUTHOR]

• Potassium ions and cyano functional groups are introduced into graphite phase carbon nitride. • The C-C bond in β−1 lignin models and aromatic vicinal diols are broken. • The production of hydroxyl radicals increases the photocatalytic efficiency. • The oxygen atom in H 2 O participates in the photocatalytic reaction. • Single electron transfer processes are possible mechanisms. Photocatalytic lignin C-C bond (LCCD) cleavage is one possible strategy to promote high-value utilization of lignin. However, it still confronts many difficulties due to the stability of the lignin structure and the high activation energy of LCCD. Herein, a graphitic carbon nitride photocatalyst with the introduction of cyano groups and K + ions (6MCN) is synthesized. Compared with pure carbon nitride (PCN), 6MCN exhibits superior photogenerated carrier separation ability, excellent sunlight capture ability, and greater oxidation capability. Under simulated sunlight, 6MCN significantly improves the photocatalytic efficiency of LCCD breakage in β-1 lignin models and aromatic vicinal diols (ACD), compared with earlier literature. The improved C β radical mechanism and single-electron transfer (SET) pathway are the primary mechanisms in the photocatalytic reaction. Hydroxyl radicals, superoxide radicals, and photogenerated holes are all involved in the photocatalytic cleavage of LCCD. However, hydroxyl radicals, as the most important active radicals, not only trigger the SET mechanism and C β radical mechanism but also provide the O and H atoms required for photocatalytic fracture of LCCD, which is very critical to obtain excellent photocatalytic efficiency. This work offers new insights into the photocatalytic breakage of LCCD in β-1 lignin models and ACD through the development of high-performance photocatalysts and the control of radical types. [Display omitted] [ABSTRACT FROM AUTHOR]

Thiophenols are chemical species with multiple desirable biological properties, including their primary and secondary antioxidant capacity. In this work, the repairing antioxidant activity of eight different thiophenols has been investigated for damaged leucine and tryptophane. The investigation was carried out employing quantum mechanical and transition state methods to calculate the thermodynamic and kinetic data of the reactions involved, while simulating the biological conditions at physiological pH and aqueous and lipidic medium. The analysis of the atomic charges and the spin densities at each of the points on the potential energy surface was the tool that allowed the elucidation of the reaction mechanisms through which thiophenols repair the oxidative damage caused to the amino acids leucine and tryptophan. It was found that thiophenols can repair leucine via a hydrogen atom transfer mechanism in a manner which is similar to the one used by glutathione to repair the carbon‐centered radicals of guanosine. In addition, thiophenols can also restore tryptophane, a nitrogen‐centered radical, via proton‐coupled electron transfer and single electron transfer mechanisms. Moreover, both processes occur at close to diffusion‐controlled rates. [ABSTRACT FROM AUTHOR]

The antiradical properties and possible mechanisms of action of the tautomers of curcumin, caffeic acid phenethyl ester (CAPE), and chicoric acid (CA) have been studied within density functional theory (DFT). We calculated global chemical reactivity descriptors from conceptual DFT, pKa, bioavailability, and toxicity to evaluate the antiradical properties and characterize these species. Our final level of theory is the M06-2X functional with the 6–31 + G* basis set; we selected this level after performing a benchmark calibration and validation among different levels. Solvent effects were modeled via the continuum solvation model based on density (SMD). We used water and pentyl ethanoate as solvents to simulate the physiological conditions. The free radical scavenger capacity was analyzed for three possible oxidative stress mechanisms: single electron transfer (SET), hydrogen atom transfer (HAT), and xanthine oxidase (XO) inhibition. The results indicate that neutral curcumin, CA, and CAPE behave as antireductants. The most favorable mechanism turns out to be HAT, where CA and CAPE stand out. In conclusion, our DFT study strongly indicates that neutral curcumin, CAPE, and CA would very likely perform well as antiradical drugs with recommended therapeutic use, supported by their non-toxic nature. [ABSTRACT FROM AUTHOR]

Recovery of bioactive compounds from distillery waste could be an option for valorizing this waste. This study investigated how the extraction of polyphenols (which have antioxidant activity) from distillery stillage was affected by solvent type and concentration, extraction time, and method of extraction (conventional solid–liquid extraction, CSLE; ultrasound-assisted extraction, UAE; microwave-assisted extraction, MAE). Although recovery was similar with UAE and MAE, 3 min MAE with 80% ethanol and 80% methanol produced the highest yields of total phenolic content (TPC), total flavonoid content (TFC) and phenolic acids. With CSLE, TPC was 2.1–1.8-times lower than with MAE and 1.7–1.4-times lower than with UAE. Increasing the solvent concentration to 100% significantly decreased recovery. Six phenolic acids were recovered (ferulic and p-coumaric acid predominated), which were present mainly in the free form. There was a significant positive correlation between antioxidant activity, as measured with three methods (one based on the hydrogen atom transfer and two based on single electron transfer mechanisms), and phenolic acid content. With MAE and UAE, polyphenols were recovered more efficiently, with 2.1 times and 1.5 times higher antioxidant activity, and with 15 times and 9 times shorter extraction times, respectively, than with CSLE; thus, they can be considered "green" alternatives to CSLE. [ABSTRACT FROM AUTHOR]

Gas-phase reactions are reliable strategies to explore the stability and activity of metal clusters, which can provide the information of products and the cluster activities by comparing the changes of the X, Y-axis of the mass spectrum before and after the reaction.Combined with ab initio calculation, we can deeply explore the structure of clusters, reaction intermediates and final products, explore the reaction thermodynamics and kinetic process,and reveal the essence and relationship between cluster structure,stability and reaction activity.In this paper,by investigating the gas-phase reaction mass spectra of Cun--clusters with NO and O2,,Agn- clusters with O2,and further combined with the ab initio calculation,novel open shell superatoms Cu18-,double closed shell superatoms Ag17- with unique stability are reported.Besides,we demonstrated the donation and back donation interactions between NO and Cun--.Chemisorption of O2 on Cu-2n+1,Cu-2n+1(or Ag-2n) clusters follows the double and single electron transfer mechanism, respectively.Among them, the behavior of O2 on Cu;;-is enabled by the spin conservation rule.By analogizing the cluster and O2 as base and acid respectively, we found a phenomenon that clusters with different alkalis pass through different degrees of spin excitation or dissociation barriers,and finally release almost the same heat for O2 dissociation. Based on this, a fully new mechanism of O2 on metal clusters was proposed: leveling effect of spin accommodation.Calculations of energy decomposition analysis-natural orbitals for chemical valence show that the activities of Cu; clusters towards NO and O2,Ag; clusters toward O2 are closely related to cluster geometry, electronic shell arrangement and energetics data. [ABSTRACT FROM AUTHOR]

Olefins are synthetically useful building blocks in modern organic synthesis. Direct functionalization of olefins; represent one of the most explored transformations in synthetic chemistry due to their easy availability and reactivity towards large number of reactants affording diverse range of organic compounds. In recent times, the development of new protocols for the functionalization of olefins is a growing realm. A plethora of olefin functionalization methodologies have been reported in the literature through ionic and free radical mechanisms including single electron transfer (SET) in the last two decades. This review gives an overview of mono‐ and difunctionalization of unactivated olefins, with an emphasis on the mechanistic details. [ABSTRACT FROM AUTHOR]

We present a simple quasi-diabatization scheme applicable to spectroscopic studies that can be applied using any wavefunction for which one-electron properties and transition properties can be calculated. The method is based on rotation of a pair (or set) of adiabatic states to minimize the difference between the given transition property at a reference geometry of high symmetry (where the quasi-diabatic states and adiabatic states coincide) and points of lower symmetry where quasi-diabatic quantities are desired. Compared to other quasi-diabatization techniques, the method requires no special coding, facilitates direct comparison between quasi-diabatic quantities calculated using different types of wavefunctions, and is free of any selection of configurations in the definition of the quasi-diabatic states. On the other hand, the method appears to be sensitive to multi-state issues, unlike recent methods we have developed that use a configurational definition of quasi-diabatic states. Results are presented and compared with two other recently developed quasi-diabatization techniques. [ABSTRACT FROM AUTHOR]

A triple-dot single-electron transistor was fabricated on silicon-on-insulator wafer using pattern-dependent oxidation. A specially designed one-dimensional silicon wire having small constrictions at both ends was converted to a triple-dot single-electron transistor by means of pattern-dependent oxidation. The fabrication of the center dot involved quantum size effects and stress-induced band gap reduction, whereas that of the two side dots involved thickness modulation because of the complex edge structure of two-dimensional silicon. Single-electron turnstile operation was confirmed at 8K when a 100-mV, 1-MHz square wave was applied. Monte Carlo simulations indicated that such a device with inhomogeneous tunnel and gate capacitances can exhibit single-electron transfer. [ABSTRACT FROM AUTHOR]

Ultra‐electron‐deficient azaacenes were synthesized via Buchwald‐Hartwig coupling of ortho‐diaminoarenes with chlorinated mellophanic diimide followed by oxidation of the intermediate N,N'‐dihydro compounds with MnO2 or PbO2. The resulting cata‐annulated bisimide azaacenes have ultrahigh electron affinities with first reduction potentials as low as −0.35 V recorded for a tetraazapentacene. Attempts to prepare a tetrakis(dicarboximide)tetraazaheptacene resulted in the formation of a symmetric butterfly dimer. [ABSTRACT FROM AUTHOR]

This communication presents a novel truncated NiII-containing metbalamin and describes its reversible one electron reduction to a catalytically active NiI species, that features cofactor F430 model character. Our results strikingly demonstrate that stabilization of NiI is not restricted to the related hydroporhyrinoid ligands and is of relevance to the application of metallocorrins in (biomimetic) catalysis. [ABSTRACT FROM AUTHOR]

The use of a carbazolyl‐connected di‐gold(I) metallotweezer for the encapsulation of several electron‐poor organic substrates, and a planar Au(III) complex containing a CNC pincer ligand, is described. The binding affinity of the receptor depends on the electron‐deficient character of the planar guest, with larger association constants found for the more electron‐poor guests. The X‐ray diffraction molecular structures of two host:guest adducts show that the host approaches its arms in order to facilitate the optimum interaction with the surface of the planar guests, in a clear example of an guest‐induced fit conformational arrangement. The electrochemical studies of the encapsulation of N,N'‐dimethyl‐naphthalenetetracarboxy diimide (NTCDI) show that the redox active guest is released from the receptor upon one electron reduction, thus constituting an example of redox‐switchable binding. [ABSTRACT FROM AUTHOR]

Photocatalytic anticancer profile of a IrIII photocatalyst (Ir3) with strong light absorption, high turnover frequency, and excellent biocompatibility is reported. Ir3 showed selective photo‐cytotoxicity against cisplatin‐ and sorafenib‐resistant cell lines while remaining dormant to normal cell lines in the dark. Ir3 exhibited excellent photo‐catalytic oxidation of cellular co‐enzyme, the reduced nicotinamide adenine dinucleotide phosphate (NADPH), and amino acids via a single electron transfer mechanism. The photo‐induced intracellular redox imbalance and change in mitochondrial membrane potential resulted in necrosis and apoptosis of cancer cells. Importantly, Ir3 exhibited high biocompatibility and photo‐catalytic anticancer efficiency as evident from in vivo zebrafish and mouse cancer models. To the best of our knowledge, Ir3 is the first IrIII based photocatalyst with such a high biocompatibility and photocatalytic anticancer therapeutic effect. [ABSTRACT FROM AUTHOR]

Electron redistribution is the cornerstone of our understanding of chemical reactivity. For the vast majority of organic reactions electrons are assumed to move in pairs providing explanatory mechanisms through the generation of intermediate structures. But for many transformations these discrete steps are idealized constructs, involving intermediates assumed but not empirically justified. This unitary perspective predicated on the curved arrow formalism has resulted in the scenario where for many organic transformations our supposed understanding far surpasses our growing knowledge. Reformulating organic mechanisms to include single electron transfer (SET) as a component of, or an alternative to, the prevailing iconic descriptions can provide for a more empirically adequate mechanistic description. In addition using the language of SET presents an opportunity to unify mechanistic concepts under a common donor/acceptor framework. [ABSTRACT FROM AUTHOR]

An antioxidant is a material that at low concentrations delays or prevents oxidation of a substrate. Antioxidant compounds act throughout several chemical mechanisms: hydrogen atom transfer (HAT), single electron transfer (SET), and the potential to chelate transition metals. The significance of antioxidant mechanisms is to understand the biological meaning of antioxidants, their possible uses, their production by organic synthesis or biotechnological methods, or for the standardization of the determination of antioxidant activity. In general, antioxidant molecules can react either by multiple mechanisms or by a predominant mechanism. The chemical structure of the antioxidant material allows understanding of the antioxidant reaction mechanism. This chapter reviews the in vitro antioxidant reaction mechanisms of organic compounds polyphenols, carotenoids, and vitamins C against free radicals (FR) and pro oxidant compounds under diverse conditions, as well as the most commonly used methods to evaluate the antioxidant activity of these compounds according to the mechanism involved in the reaction with free radicals and the methods of in vitro antioxidant evaluation that are used commonly depending on the reaction mechanism of the antioxidant. [ABSTRACT FROM AUTHOR]

This work has described the synthesis, characterization, spectral and electrochemistry properties of bis-(phthalocyanine) lutetium(III) bearing halogenated (F, Cl and Br) phenoxy- phenoxy groups. [Display omitted] • Bis-(phthalocyaninato) lutetium(III) complexes containing halogenated (F, Cl and Br) phenoxy-phenoxy groups were synthesized. • Characteristic radical Pc reduction reactions supporting the sandwich structure of the complexes were recorded. • Complexes have distinct color changes during redox reactions. • It was determined that the redox activities can be manipulated by changing the concentrations of the complexes. • The spectral and color changes observed during electron transfer prove the applicability of these complexes in various imaging technologies. The synthesis, characterization, spectral, and electrochemical properties of bis-(phthalocyanine)lutetium (III) (LuPc 2) bearing halogenated (F (F-LuPc 2), Cl (Cl-LuPc 2) and Br (Br-LuPc 2)) phenoxy groups were reported for the first time. To explore the possible application of the LuPc 2 complexes, their detailed redox mechanisms were determined by voltammetric and spectroelectrochemical characterizations. One of the Pc rings exhibits radical characteristics as a result of the sandwich structures of the complexes, which led to the typical one electron reduction process between 0.20 and 0.40 V and the typical one electron oxidation process between 0.60 and 0.80 V. In addition to the characteristic Pc. - L u 3 + Pc 2 - / Pc 2 - L u 3 + Pc 2 - 1 - reduction and Pc. - L u 3 + Pc 2 - / Pc. - L u 3 + Pc. - 1 + oxidation couple of the complexes, further two-electron reduction and oxidation processes were also observed due to the simultaneous electron transfer reactions of each Pc ring at very close potentials. Moreover, at more negative potentials sequential one electron reduction waves for each Pc ring were also observed. While the Cl-LuPc 2 reduced at less positive potential and more negative potential, changing Br with Cl and F alters the ease of the electron transfer reactions of the complexes. In situ spectroelectrochemical results supported these voltammetric assignments. Moreover, distinct color changes of LuPc 2 in the solution observed with in situ spectroelectrochemical measurements indicated their functionality as electrochromic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Some properties of Kojic acids were investigated by density functional theory. • Natural bond orbital data showed two types of significant hydrogen bonds in 1 – 12. • The aromaticity indices showed that the ring in the conjugated acids is aromatic. • The type of X and Y heteroatoms affect the antioxidant activity of 1 – 12. The 4-pyrone scaffold inherent in Kojic acid demonstrates substantive biological attributes. This present inquiry delves into the structural and electronic characteristics of twelve Kojic acid derivatives employing the DFT/B3LYP 6–311++G(d, p) methodology, scrutinizing their behavior in the gas phase and water. Aromaticity indices reveal the aromatic nature of the six-membered rings within the conjugated acids of these compounds. Notably, compound 10 , housing an imine group, exhibits heightened basicity surpassing that of 1,8-bis(dimethylamino)naphthalene, potentially categorizing it as a superbase. The assessment of antioxidant activity encompasses both hydrogen atom transfer and single electron transfer-proton transfer mechanisms, revealing a discernible impact of X and Y heteroatoms on the antioxidant activity of structures 1 – 12. [ABSTRACT FROM AUTHOR]

[Display omitted] • Building C vacancy and C-F site on g-C 3 N 4 boosted OBS degradation in PCO process. • FCN_Cv had an enhanced E CB , narrower band gap and longer e- lifetime over BCN. • O 3 was activated by one electron reduction and photocatalytic peroxone reaction. • OH was the main ROS for degrading OBS. Photocatalytic ozonation (PCO) was a novel water treatment method, but the low photo-generated electron (e-) utilization and ambiguous ROS formation mechanism restrained its performance. Herein, C vacancy and F co-decorated g-C 3 N 4 (FCN_Cv) was designed to accelerate the PCO performance with sodium p -perfluorinated nonoxybenzenesulfonate (OBS) acting as model pollutant. Comparative characterizations revealed that FCN_Cv remained the inherent structure of g-C 3 N 4 (BCN), and had an enhanced conduction band potential, narrower band gap and longer e- lifetime. FCN_Cv exhibited the greater activity over BCN, with 99.3 % OBS removal in 30 min but only 78.3 % for BCN during PCO process. •OH was the main ROS for degrading OBS. The greater •OH yield was obtained by FCN_Cv PCO process because of the increase of e- utilization. On one hand, the two electrons reduction of O 2 into H 2 O 2 on FCN_Cv was accelerated, which triggered the peroxone reaction between photogenerated-H 2 O 2 and O 3. On the other hand, the direct one electron reduction of O 3 by e- also accounted for •OH generation. 17 kinds of intermediates were detected and the OBS degradation routes were inferred, which was involved with hydroxylation, C-O cleavage and aromatic ring opening reactions. Overall, this study demonstrated the feasibility of decorating F element and C vacancy on g-C 3 N 4 in enhancing e- utilization and •OH generation during PCO process as well as deepened the understanding of fate of OBS in PCO process. [ABSTRACT FROM AUTHOR]

A visible‐light‐mediated reaction of N‐phenylpropynamides with diethyl 2,2‐dibromomalonate for the synthesis of bromo‐substituted azaspirotrienediones has been developed. This method allows the formation of C−Br, C−C and C=O bonds in one pot via a cascade radical addition/ipso‐cyclization/oxidation process. A possible radical mechanism involving single electron transfer and energy transfer processes is proposed based on control experiments, cyclic voltammetry determination and Stern‐Volmer quenching experiments. [ABSTRACT FROM AUTHOR]

The synthesis of a novel bisacridinium-Zn(II) porphyrin is reported and its properties investigated via electrochemical, photophysical and computational studies. Cyclic voltammetry studies revealed a two-electron oxidation of the Zn(II) porphyrin and the simultaneous one electron reductions of the two acridiniums. Using absorption, emission and ultrafast transient absorption spectroscopies, the near total fluorescence quenching observed following excitation of either the acridinium or Zn(II) porphyrin units was assigned to ultrafast electron transfer (≤0.3 ps) leading to a reduced acridinium and an oxidized porphyrin unit in the bisacridinium-Zn(II) porphyrin conjugate. In addition, computational studies were found to complement experimental results, with calculations revealing two near degenerate HOMOs for the porphyrin. [ABSTRACT FROM AUTHOR]

This work describes the preparation of a new thiosemicarbazone derivative, (Z)-N-ethyl-2-(6-oxo-1,10-phenanthrolin-5(6H)-ylidene)hydrazinecarbothioamide (phet) and its respective Re(I) tricarbonyl chloro complex, fac-[ReCl(CO)3(phet)]. The spectroscopic, photophysical and electrochemical properties of the new complex were fully investigated through steady state and time-resolved techniques along with computational calculations. In fac-[ReCl(CO)3(phet)], the new ligand is coordinated to the metal center through the pyridyl rings of the phenanthroline moiety. The unbound electron pairs in the S atom of the bending thiosemicarbazone group induce new low energy lying electronic transitions. Consequently, enhanced visible light absorption up to 550 nm is observed in acetonitrile due to the overlap between MLCTRe→phet and ILphet(n→π*) transitions. The absorption bands and emission quantum yields of fac-[ReCl(CO)3(phet)] are sensitive to proton concentration due to an acid-basic equilibrium in the N atoms of the thiosemicarbazone. Proton dissociation constants of 10.0 ± 0.1 and 11.4 ± 0.2 were determined respectively for the ground and excited states of the new complex. Spectral changes could also be observed in the presence of Zn2+ cations which can be further explored for sensing applications. The electrochemical behavior of the new complex was studied in detail, revealing up to four one electron reduction processes in the range from 0 to −2.4 V vs. Fc+/Fc. With support of DFT calculations, the first three processes are ascribed to the reduction of the coordinated phet ligand followed by the ReI/0 reduction and consequent Cl− release. The new complex was able to act as an electrocatalyst for CO2 reduction into CO (Eonset = −1.92 V vs. Fc+/Fc), with a turnover frequency of 2.81 s−1 and turnover number of 24 ± 1 in anhydrous acetonitrile, being the first Re(I) tricarbonyl complex with a thiosemicarbazone derivative described for this goal. The detailed characterization carried out here can drive the development of new Re(I)-thiosemicarbazone derivatives for different applications. [ABSTRACT FROM AUTHOR]

One electron reduction of formally CoIV(OR)2(CPh2) forms the [CoII(OR)2(CPh2)]− anion. Whereas low-spin Co(OR)2(＝CPh2) demonstrated significant alkylidene character, the high-spin [Co(OR)2(CPh2)]− anion features a rare Co(II)–carbene radical. Treatment of [Co(OR)2(CPh2)][CoCp*2] with xylyl isocyanide triggers formation of two new C–C bonds, and is likely mediated by nucleophilic attack of deprotonated CoCp*2+ on a transient ketenimine. [ABSTRACT FROM AUTHOR]

Electrochemistry offers opportunities to promote single-electron transfer (SET) redox-neutral chemistries similar to those recently discovered using visible-light photocatalysis but without the use of an expensive photocatalyst. Herein, we introduce a microfluidic redox-neutral electrochemistry (mRN-eChem) platform that has broad applicability to SET chemistry, including radical-radical cross-coupling, Minisci-type reactions, and nickel-catalyzed C(sp2)–O cross-coupling. The cathode and anode simultaneously generate the corresponding reactive intermediates, and selective transformation is facilitated by the rapid molecular diffusion across a microfluidic channel that outpaces the decomposition of the intermediates. mRN-eChem was shown to enable a two-step gram-scale electrosynthesis of a nematic liquid crystal compound, demonstrating its practicality. [ABSTRACT FROM AUTHOR]

The Fenton method is an important water treatment process. However, the mechanism of the Fenton reaction is still not widely recognized. In this article, the autocatalysis process responsible for the degradation of 4-chlorophenol (4-CP) as well as the generation of Fe(II) and the decomposition of H2O2 is elaborated using a Fe(III)/H2O2 system. It was found that the one electron reduction of Fe(III) to Fe(II) via oxidization of H2O2 to ˙HO2 is not spontaneous according to the standard electrode potential rather than being limited by the rate constant of 0.0027 M−1 s−1 in view of the Haber–Weiss circulation. However, the reaction of Fe(III) and 4-CP is spontaneous with a second-order kinetic rate constant of >0.12 M−1 s−1 and a conversion rate of 0.56%, which triggers the switch of the Fenton-like reaction as a real rate-determining step. The circulation of Fe(III) to Fe(II) in the proposed Fenton-like reaction mechanism depends on the organic species and various intermediates, which indicates its reaction selectivity, preferable for organics with a stronger thermodynamic and kinetic activity. Besides, a slight pH decline with time-scale and the stoichiometric ratio of ˙OH to H2O2 and H2O2 to 4-CP being 1 and 2, respectively, pointed to the new proposed reaction mechanism. The discovery of the new reaction mechanism might promote the theoretical and technical advancement of the Fenton-like process. [ABSTRACT FROM AUTHOR]

Employing a two‐dimensional covalent organic framework as the reusable solar photosensitizer, the sunlight‐driven aerobic oxidative construction of a nitrogen‐sulfur bond has been achieved. 3,5‐Disubstituted 1,2,4‐thiadiazoles are smoothly prepared in water by using this procedure. Furthermore, a radical mechanism with a sunlight‐promoted single electron transfer (SET) process is proposed for this transformation. [ABSTRACT FROM AUTHOR]