Acidic Proton Research Articles

Reductive Photocatalytic Proton-Coupled Electron Transfer by a Zirconium-Based Molecular Platform.

Reductive proton-coupled electron transfer (PCET) has important energetic implications in numerous synthetic and natural redox processes. The development of catalytic systems that can mediate such transformations has become an attractive target, especially when light is used to generate the reactive species towards solar-to-chemicals conversion. However, such approach becomes challenged by kinetic competition with H2 evolution. Here we describe the excited state reactivity of a molecular Zr-based platform under visible light irradiation for the efficient reduction of multiple bonds. Mechanistic investigations shine light on a charge separation process that colocalizes an excited electron and an acidic proton to promote selective PCET. We further leveraged this reactivity for the photocatalytic reduction of a variety of organic substrates. Our results demonstrate the promise of this molecular platform to design strong photocatalytic PCET mediators for reductive transformations. More broadly, we also show the potential relevance of PCET mechanisms in the (photo)redox chemistry of Zr-based molecular materials.

Reductive Photocatalytic Proton‐Coupled Electron Transfer by a Zirconium‐Based Molecular Platform

AbstractReductive proton‐coupled electron transfer (PCET) has important energetic implications in numerous synthetic and natural redox processes. The development of catalytic systems that can mediate such transformations has become an attractive target, especially when light is used to generate the reactive species towards solar‐to‐chemicals conversion. However, such approach becomes challenged by kinetic competition with H2 evolution. Here we describe the excited state reactivity of a molecular Zr‐based platform under visible light irradiation for the efficient reduction of multiple bonds. Mechanistic investigations shine light on a charge separation process that colocalizes an excited electron and an acidic proton to promote selective PCET. We further leveraged this reactivity for the photocatalytic reduction of a variety of organic substrates. Our results demonstrate the promise of this molecular platform to design strong photocatalytic PCET mediators for reductive transformations. More broadly, we also show the potential relevance of PCET mechanisms in the (photo)redox chemistry of Zr‐based molecular materials.

Roles of Acidic Proton for Fe-Containing Zeolite in Direct Oxidation of Methane

Roles of Acidic Proton for Fe-Containing Zeolite in Direct Oxidation of Methane

Physical and Chemical Dual Confinement Promotes Controllable Synthesis of Loose-Structured Azine-Linked Nanofilms for Fast Molecular Separation.

Thin-film composite (TFC) membranes, featuring nanoscale film thickness and customizable pore structures, hold promise for solute-solute separations. However, achieving on-demand molecular sieving requires fine control over the membrane microstructure. Here, the concept of physical and chemical dual confinement (PCDC) is introduced to fabricate loose-structured TFC membranes via confined interfacial polymerization (IP). This concept leverages the synergistic effects of physically restricted monomer diffusion and a chemically inhibited reaction to achieve controlled nanofilm growth. Dorsal addition of the aqueous phase to the hydrogel reduces the diamine diffusion via electrostatic and H-bonding interactions within its nanopores. The prepassivation of hydrazine using acid protonation effectively weakens its ability for nucleophilic reactivity. This confined IP between twisted TFPA and short-chain hydrazine yielded loosely structured azine-linked nanofilms, which displayed a high permeability of 53.4 LMH bar-1 and effective differentiation of binary mixtures. This PCDC concept offers a useful guideline to finely tailor polymeric nanofilms for precise separations.

The Fate of the Formic Acid Proton on the Anatase TiO2(101) Surface

AbstractAs a prototype adsorption reaction of gas Brønsted acid on oxides, we study the adsorption of formic acid on anatase. We perform infrared spectroscopy measurements of adsorbed HCOOH and HCOOD on TiO2 nanopowders, from 13 K up to room temperature in an ultra‐high vacuum chamber. We assign the IR signals via computed spectra from nuclear quantum dynamics simulations using our divide‐and‐conquer semiclassical ab initio molecular dynamics method. The acid proton forms an extraordinarily short and strong hydrogen bond with the surface oxygen. The strength of this hydrogen bond, that compares to H bonds in ice at high pressures, is at the root of a substantial redshift with respect to the typical free OH stretching frequency, which eludes its straightforward detection.

Selective Detection of Divalent Cations (Cu2+, Zn2+, Pb2+) and Anions (SO42-, S2-, CO32-) Using a pH-Sensitive Multi-functional Schiff Base inNeutralMedium.

A new Schiff base-based multi-cation/anion probe (L) has been synthesized and characterized using HR-MS, FT-IR, 1H, and 13C NMR techniques. The Schiff base motif provides specific binding sites that detect cations and anions by generating distinct optical output signals upon interaction. A noticeable color change of the probe solution was observed from pale yellow to various shades of yellow upon adding cations such as Cu2+, Zn2+, and Pb2+ and anions such as CO32⁻, S2⁻, and SO42⁻. This color change results from forming complexes like M3L2 with metal ions. Whereas origin of color in presence of anion were attributed due to the deprotonation of acidic proton in the ligand. Moreover, the complexes formed by Zn2+, S2/CO32⁻ ion with L are fluorescent, enabling the detection of Cu2+ and SO42⁻ using the Stern-Volmer plot, with a limit of detection (LODs) of 8.48µM and 10.47µM, respectively. Additionally, increasing the pH of the probe solution above 8 reveals a significant enhancement of fluorescence intensity due to the deprotonation of phenolic -OH and amide -NH in the presence of hydroxide ions. This emission in the basic medium is quenched by Cu2+ ions and restored when Cu2+ is complexed with EDTA. A logic gate has also been constructed for understanding the TURN-OFF-TURN-ON mechanism involving Cu2+ ions and EDTA. Overall, the versatile performance of a single probe L opens up new possibilities as a multifunctional sensor, making it highly suitable for practical applications.

Oxyanion Engineering on RuO2 for Efficient Proton Exchange Membrane Water Electrolysis

AbstractIn acidic proton exchange membrane water electrolysis (PEMWE), the anode oxygen evolution reaction (OER) catalysts rely heavily on the expensive and scarce iridium‐based materials. Ruthenium dioxide (RuO2) with lower price and higher OER activity, has been explored for the similar task, but has been restricted by the poor stability. Herein, we developed an anion modification strategy to improve the OER performance of RuO2 in acidic media. The designed multicomponent catalyst based on sulfate anchored on RuO2/MoO3 displays a low overpotential of 190 mV at 10 mA cm−2 and stably operates for 500 hours with a very low degradation rate of 20 μV h−1 in acidic electrolyte. When assembled in a PEMWE cell, this catalyst as an anode shows an excellent stability at 500 mA cm−2 for 150 h. Experimental and theoretical results revealed that MoO3 could stabilize sulfate anion on RuO2 surface to suppress its leaching during OER. Such MoO3‐anchored sulfate not only reduces the formation energy of *OOH intermediate on RuO2, but also impedes both the surface Ru and lattice oxygen loss, thereby achieving the high OER activity and exceptional durability.

Computational Justification Towards Detection of Dual Anions on a Single Molecular Platform: The Role of Solvent in Decoration of Dual Channels

ABSTRACTRatiometric optical detection of analytes is a convenient strategy as the technique is devoid of relative error and background correction. Herein, solvent‐guided ratiometric optical recognition of fluoride and bisulfate anions by a low‐cost, “off‐the‐shelf” bioactive molecule, harmane (HRH) is thoroughly explored. Interestingly, solvent plays a dynamic role in the selective recognition of the dual anions via the dual channels of HRH in an intelligent manner. The probe displays high‐fidelity recognition behavior towards fluoride ion in an aprotic solvent (acetonitrile) and towards bisulfate ion in a protic environment (acetonitrile/water; 5:1; v/v). Both the channels of HRH are very selective for a particular anion (F−/HSO4−) in a specific solvent. Organized and comprehensive theoretical calculation denotes that hydrogen bonding between the acidic pyrrolic proton of HRH and fluoride for the first channel and the acidic proton of bisulfate and the pyridinic nitrogen for the second channel of HRH led to the formation of a hydrogen‐bonded ion pair (HBIP). Consequently, significant optical changes are observed in the visible region, which is convenient for real‐life detection of F− and HSO4− independently. The essential role of solvent in tuning the dual channels of HRH is an important artifact in the literature of fundamental photochemistry.

Pyrazine-Based Iodine-Containing Biocidal Materials: Enhanced Energy Performance and Reduced Corrosion Risk.

Biosafety is crucial to the common interests of all humanity. Currently, global biosafety governance is a challenge and poses significant opportunities. With the escalating challenges posed by microorganisms, there is an urgent need to develop advanced biocidal materials. In this work, we introduce a class of iodine-containing high-energy biocidal materials, utilizing pyrazine rings with good thermal stability as nitrogen-rich high-energy backbones, to address the issues of corrosion and hygroscopicity associated with N-H acidic protons in traditional iodine-containing azole compounds. Employing nucleophilic substitution and coupling reactions, we successfully synthesized two distinct series of eight compounds (Series A: BQDI, BQFI, BQDIO; Series B: BBQ3I, BBQ4I, BBQNI, MBQ5I, and MBQDI), which exhibit a high iodine content and enhanced detonation pressure. Notably, compounds BQDIO and BBQNI show detonation pressures of 13.70 and 16.52 GPa, respectively, both exceeding the 10 GPa of traditional iodine-containing biocidal materials. This improvement is crucial for expanding the diffusion range of biocidal substances and enhancing the biocidal efficiency of these materials. Pyrazine-based iodine-containing compounds have revolutionized the performance of biocidal materials, addressing corrosion issues and paving the way for the development of efficient, stable, and safe biocidal materials.

Efficacy and Safety of Potassium-competitive Acid Blockers Versus Proton Pump Inhibitors in Treating Erosive Esophagitis: A Meta-analysis Based on Randomized Controlled Trials.

This meta-analysis aimed to investigate the efficacy and safety of potassium-competitive acid blockers (P-CABs) and proton pump inhibitors (PPIs) in treating erosive esophagitis (EE). PubMed, Embase, Cochrane Library, and Web of Science were systematically searched using predefined search terms up to January 2024. Relevant randomized controlled trials were included. The outcoming were the EE healing rate and treatment-related adverse events incidence. Nine randomized controlled trials involving 4012 patients were included. Patients receiving P-CAB exhibited a significantly better overall healing rate compared with PPI at week 2 [risk ratio (RR) = 1.06], but no statistical difference was observed at week 4 and week 8. Subgroup analysis revealed that P-CAB demonstrated a higher healing rate for patients with Los Angeles (LA) grade C/D, regardless of the assessment at week 2 (RR = 1.17), week 4 (RR = 1.10), or week 8 (RR = 1.08). However, no significant difference was found between PPI and P-CAB for patients with LA grade A/B at week 2, week 4, or week 8. Furthermore, patients treated with P-CAB had lower recurrence rates during maintenance therapy compared with PPI (RR = 0.79). In terms of safety, P-CAB was associated with a lower incidence of headache compared with PPI (RR = 0.32), with no statistical difference found in any treatment-related adverse events between the two groups. P-CAB was found to be safe and effective for EE treatment compared with PPI, particularly in 2-week short-term treatment, severe EE (LA grade C/D) treatment, or maintenance therapy. Limitations such as potential heterogeneity among included trials should be considered in the interpretation of these findings.

The influence of functional groups on the pyrolysis of per- and polyfluoroalkyl substances

Thermal treatment is a widely used remediation strategy for PFAS-contaminated materials such as soil, spent sorbents, and domestic waste. To better understand the effectiveness and environmental impact of thermal treatments for PFAS-contaminated materials, a fundamental understanding of PFAS thermal degradation mechanisms is required. This work aims to study the pyrolysis of six representative PFAS compounds, all of which have an eight-carbon length but with different functional groups. To assess the thermal stability and pyrolysis products of these six PFAS compounds, evolved gas analysis (EGA) was performed using thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) coupled with an infrared spectrometer (IR) and a mass spectrometer (MS), as well as pyrolysis-GCMS (Pyr-GCMS). The EGA data demonstrates that compounds with lower estimated vapor pressures were generally found to be more thermally labile, and the presence of an ionic bond necessitates higher temperatures for pyrolysis. Pyrolysis at 900 °C yielded a variety of fluorinated organic compounds at significant signals. Tetrafluoroethene constituted the majority of the Pyr-GCMS signal for all the compounds. Moreover, a significant fraction of detected products was unable to be identified, underscoring a need for better tools to help with the identification of unknowns. Pyrolysis can occur through random chain scission, scission of the functional group, scission of the terminal CF3 group, and HF elimination. Some compounds may undergo more complete beta-scission to produce smaller pyrolysis products compared to others. The presence of acidic protons within the functional group can help facilitate HF elimination, whereas the salt form of a PFAS compound is less likely to undergo HF elimination. Termination of radical intermediates can either be recombination with a CF3 radical or hydrogen abstraction (H-abstraction). Observed hydrogen-substituted products indicate that functional groups with higher hydrocarbon character may lead to more H-abstraction terminated products. Overall findings show that the functional group of a PFAS may decrease or increase its thermal stability and lead to different profiles of pyrolysis products.

Synthesis, structures, and cytotoxicity insights of organotin(IV) complexes with thiazole-appended pincer ligand

Diorganotin complexes of the compositions [Me2Sn(L)] (1), [n-Bu2Sn(L)] (2), [Ph2Sn(L)]⋅C6H6 (3), [Bz2Sn(L)]⋅C6H6 (4) and [n-Oct2Sn(L)] (5) were synthesized by reacting R2SnO (R = Me, n-Bu, Ph, Bz or n-Oct) with the N2,N6-di(thiazol-2-yl)pyridine-2,6-dicarboxamide (H2L, where H2 denotes the two acidic protons) in refluxing toluene. Additionally, the mono-n-butyltin complex [n-BuSn(HL)Cl2]·H2O (6) was synthesized from n-BuSnCl3 and H2L in acetonitrile. Compounds were characterized by FT-IR, 1H, 13C and 119Sn NMR spectroscopy, while their solid-state structures were examined using single-crystal X-ray diffraction studies. In diorganotin compounds 1–5, the dianionic tridentate ligands (Npy, N−, N−) act as κ-N3 chelators. In 6, the L moiety (O, Npy, N−) acts as a κ-ON2 tridentate chelator, with involvement of one of the carboxamide oxygen atoms. The coordination polyhedron around the Sn(IV) ion is completed either by two axial Sn-R ligands in compounds 1–5 or by n-Bu and Cl ligands in compound 6, giving rise to distorted trigonal bipyramid or octahedral structures, respectively. The tin NMR results show that the penta-coordinated structures of compounds 1–5 and the hexacoordinated structure of compound 6, observed in the solid-state, are retained in solution. The in vitro antitumor activities of 1–5 were tested on T-47D breast cancer cells. Of these, diphenyltin compound 3 showed the highest anti-proliferative effect, with an IC50 of 10 ± 1.60 μM. Compound 3 exhibited selective toxicity, potentially inducing apoptosis via reactive oxygen species generation and nuclear changes, indicating promise as a breast cancer treatment. This study is the first to explore thiazole-appended organotin compounds for cytotoxicity.

Novel MCRs of Isatins: Green Synthesis and Theoretical Study of Novel Thiazinoazepines

This study examined the utilization of an intricate procedure including isatin, α-haloketones, electron-deficient acetylenic chemicals, ammonium acetate, and isothiocyanates in an aqueous solution at standard room temperature. The objective was to produce new thiazinoazepine compounds with substantial yields. The synthesized thiazinoazepines possess NH functional groups with acidic protons and exhibit significant antioxidant action. The synthesized compounds demonstrated antibacterial efficacy against both Gram-positive and Gram-negative bacteria, as evaluated by the disk diffusion method. Quantum chemical methods based on density functional theory have been employed to improve understanding of reaction mechanisms. The employed methodology for the synthesis of thiazinoazepines offers numerous benefits, such as swift reaction kinetics, exceptional product yield, and uncomplicated product isolation.

Stability under electron irradiation of some layered hydrated minerals

The structural damages caused to some layered hydrated minerals by 2.5 MeV electron irradiation using the SIRIUS platform were studied by powder X-Ray diffraction and, in some cases, by 1H MAS-NMR spectroscopy. It is clearly demonstrated that the radiation damages are distinguishable from the heating effects. It is shown that: i) in all cases electron irradiation leads to distortions of the unit cell and very limited volume expansion, compared to heating; ii) radiation damages increase with increasing the structural complexity of the mineral; iii) portlandite Ca(OH)2 and brucite Mg(OH)2 remain crystalline up to high doses (a few GGy), with appearance of stacking fault disorder especially in brucite; iv) brushite CaHPO4.2H2O and gypsum CaSO4.2H2O undergo a phase transformation of type amorphization for brushite involving the strongest intralayer H bond between the acidic proton and the phosphate tetrahedral, and decomposition for gypsum involving interlayer H bonds between water molecules.

Antibacterial of PSf substrate and PA active layer of TFN membrane made by POM/3-API hybrid in situ FO separation performance and photo-degradation of organic pollutant

Membrane bacterial studies are stable in modified FO membrane that shows superior antibacterial activity against Tetrasphaeria (minimal inhibitory concentration (MIC) = 0.00350, 0.11 μg/mL). Due to augmented interventions of the containments in the water resources, essential novel hybrids construct of polyoxometalate with imidazole for the separation process and photo catalytic degradation of organic pollutants have been recognized and scouted in this paper. This work demonstrated the separation and photocatalytic extraction of the organic pollutants from the potable and waste water using organo-polyoxometalate ionic salts as hybrids designated as polyoxometalate with 3-(aminopropyl) imidazole (POM/3-API). Hybrid materials are strategically prepared in one-pot via counter acidic proton exchange between POM (O- ions) which tends to move towards N- containing organic molecules, which are doped with manganese (IV) ions. Scanning Electron Microscope (SEM) studies show physico-chemical adsorption of the hybrids, PSf substrate and on PA layer of membranes, proving the multifunctional surface characteristics morphological formation. In addition, POM/3-API hybrids were synthesized via shock acoustic that reveals higher permeate flux through separation process and almost disappears (PAPI-1: 81.4 %) with MO during degradation process. Remarkably, the morphological changes of observed shapes before and after MO clearly show an effective performance, as was definite by the successful interfacial polymerization between membrane and POM/3-API. These help towards elimination of MO dyes at waste water sources, making the process environment-friendly.

Efficacy of Potassium-competitive Acid Blockers versus Proton Pump Inhibitors in First- and Second-line Eradication Regimens for Helicobacter pylori in Egyptian Patients

Efficacy of Potassium-competitive Acid Blockers versus Proton Pump Inhibitors in First- and Second-line Eradication Regimens for <i>Helicobacter pylori</i> in Egyptian Patients

An effective strategy to enhance phosphoric acid retention and proton conductivity stability: Construction of proton transfer channels with starch rather than H3PO4

To enhance the phosphoric acid (PA) retention as well as maintain high proton conductivity of phosphoric acid doped proton exchange membranes at high temperature, we successfully design a series of phosphoric acid doped biobased composite membranes by incorporation of starch and graphene oxide (GO) into poly arylene ether ketones (PAEK). Proton transfer channels should be mainly built through dense hydrogen bonds formed from massive oxygen-containing groups of starch mainchain, which is confirmed by Molecular dynamics (MD) simulation, FT-IR and XRD analysis. The dense hydrogen-bond structure could construct fast proton transfer channels with extreme low doping level (0.00484 molH3PO4). The excellent PA retention properties with almost unchanged proton conductivity at high temperature (200 °C) for 600 min indicates that PA molecules are firmly fixed into membranes. Thus, in this study, we suggest a novel strategy for stablizing proton conductivity at high temperature and improving PA retention properties of PA doped membranes, which is building dense hydrogen-bond structure with low PA doping level.Based on the results in this study and the Grotthuss proton transfer mechanism, dense hydrogen-bonds from oxygen-containing groups in polymer backbones should be more stable than hydrogen-bonds from massive H3PO4 molecules with high acid doping levels to promote proton conduction.

Current Advances in Diagnosis, Therapeutics, and Surgical Interventions for the Management of Refractory Gastroesophageal Reflux Disease (GERD): An Update.

Gastroesophageal reflux disease (GERD) is a chronic illness characterized by complications arising from the reflux of stomach contents, which significantly lower the quality of life, increase morbidity, and increase medical expenses associated with treating the condition. The main goal of treatment in GERD is symptomatic relief, relapse prevention, and healing of erosive esophagitis. The treatment mainly involves lifestyle changes to control acid production and proton pump inhibitors (PPIs) as the first line of treatment. Endoscopic interventions or anti-reflux surgery may be beneficial in relieving symptoms in people whose symptoms are triggered by reflux. In this review, we discuss the pathophysiology and newer diagnostic and treatment modalities including available surgical management options to manage refractory GERD.

Molecular modelling of luciferyl adenylate deprotonation in the active site of Photinus pyralis luciferase

Firefly bioluminescence is a product of chemical reactions that involve luciferin chromophore oxidation in the active site of luciferase proteins. We perform a series of classical molecular dynamic simulations and combined quantum and molecular mechanics (QM/MM) calculations to expose the molecular mechanism of C4 carbon atom deprotonation in luciferyl adenylate molecule. QM/MM calculations confirm that ND-protonated His245 residue is a suitable proton acceptor in the wild-type Photinus pyralis luciferase. Classical molecular dynamic simulations reveal oxygen-binding cavities inside the protein including the one located close to the C4 atom of luciferin. In mutant forms that lack direct interactions with the His245 side chain, a proton wire comprising water molecules stimulates either protonation of the phosphate group of the luciferyl adenylate forming an unstable intermediate or keto–enol tautomerisation of luciferin. The comparison of the ionisation potentials of molecular systems with the ‘deprotonated’ C4 carbon atom revealed that the ionisation energy for the enol tautomeric form is close to the system with the His245 proton acceptor. Thus, the existence of the keto–enol tautomerisation channel might explain bioluminescence in case of the absence of the amino acid proton acceptor.

Efficacy and Safety of Potassium-Competitive Acid Blockers vs Proton Pump Inhibitors for Peptic Ulcer Disease or Postprocedural Artificial Ulcers: A Systematic Review and Meta-analysis.

Peptic ulcer disease (PUD) and postprocedural artificial ulcers are common ulcer disease. For them, proton pump inhibitor (PPI) and potassium-competitive acid blocker (P-CAB) are commonly used in clinical practice. PPI requires acid, time, and multiple doses, but P-CAB has fewer limitations. We compared the efficacy, safety, and prevention of PPI and P-CAB in PUD or artificial ulcer. We searched PubMed, ClinicalTrials.gov , Embase, Cochrane Library, and Web of Science databases for all studies. All eligible randomized controlled trials up to August 5, 2023, were included. Healing rates, shrinking rates, treatment-emergent adverse events rates, and recurrence rates were measured. Risk of bias, sensitivity analyses, and heterogeneity were also performed. Twenty researches that were selected from 926 screening studies and in total 6,551 participants were included. The risk ratio (RR) of healing rate with P-CABs vs PPIs of PUD at 4 weeks was RR 1.01 (95% confidence interval 0.98-1.04). In addition, the healing rate distinction of artificial peptic ulcer was RR 1.04 (0.89-1.22), and the shrinking rate was mean difference 0.10 (-1.30-1.51). The result of treatment-emergent adverse event rate of PUD was RR 1.11 (0.91-1.35), and the delayed bleeding rate of artificial ulcer was RR 0.35 (0.16-0.80). The RR for recurrence rate of drug-related ulcers was 0.45 (0.25-0.81). P-CAB is noninferior in healing artificial ulcer and PUD, also the incidence of treatment-emergent adverse events. But, there may be a statistical advantage in holding back delayed bleeding and preventing drug-induced ulcers. More standardized experiments are needed for further applications and more precise conclusions.