Hydroxyl Hydrogen Research Articles

Efficient degradation and deiodination of iopamidol by UV/sulfite process: Assessment of typical process parameters and transformation paths.

Iopamidol (IPM) is widely used in medical clinical examination and treatment and has immeasurable harm to the ecological environment. The combination of UV and sulfite (UV/sulfite) process was developed to degrade IPM in this study. In contrast to that almost no removal of IPM was observed under sulfite reduction alone, the UV/sulfite process could efficiently reductively degrade IPM with the observed rate constant (kobs) of 2.08 min-1, which was nearly 4 times that of UV irradiation alone. The major active species in the UV/sulfite process were identified as hydrated electrons (eaq-) by employing active species scavengers. The influence of the initial pH, sulfite dosage, IPM concentration, UV intensity and common water matrix were evaluated. The degradation of IPM reached nearly 100% within only 2.5 min at pH 9, and kobs increased at higher initial sulfite dosages and greater UV intensities. HCO3- had a limited effect on the degradation of IPM, while humic acid (HA) was found to be a strong inhibitor in the UV/sulfite process. With the synergistic action of UV/sulfite, most of the iodine in IPM was found to release in the form of iodide ions (up to approximately 98%), and a few formed iodide-containing organic compounds, reducing significantly the toxicity of degradation products. Under direct UV irradiation and free radical reduction (mainly eaq-), 15 transformation intermediates of IPM were produced by amide hydrolysis, deiodination, hydroxyl radical addition and hydrogen abstraction reactions, in which free radical attack accounted for the main part. Consequently, the UV/sulfite process has a strong potential for IPM degradation in aquatic environments.

Microwave spectra of two conformers of the (1R)-(–)-nopol monomer

The rotational spectrum of the (1R)-(-)-nopol monomer has been observed in the 6–18 GHz region using CP-FTMW spectroscopy. Transitions of two distinct conformers of the parent isotopologue have been observed and assigned. Density Functional Theory (DFT) calculations performed on the monomer predict nine distinct low-energy heavy atom geometries. The differences between these structures are attributed to changes in the orientation of two dihedral angles in the heavy atom R-CH2CH2OH functionalization, where R refers to the fixed bicyclic cage component of the molecule. Further optimization of these geometries found 27 distinct conformers associated with the hydroxyl hydrogen orientation. The rotational constants of the two lowest energy conformers were found to be in good agreement with the experimental constants of the two observed conformers and the predicted dipole moment components agree with the relative intensities of the observed transitions.

Size-effect on the intracellular antioxidative activity of Prussian blue nanoparticles investigated by atomic force microscopy

Nanoparticles-based antioxidative therapy has been highlighted in a series of diseases triggered by excessive reactive oxygen species (ROS). Prussian blue nanoparticles (PBNPs), as a representative artificial nanozyme, have been proved as highly effective ROS scavengers. However, its detailed intracellular antioxidant mechanism is not clear yet. Herein, a series of PBNPs with different particle sizes were synthesized and their intracellular antioxidant activities were studied by atomic force microscopy (AFM) from a biomechanical perspective. We first validated the ROS scavenging ability of PBNPs in vitro. It indicated that PBNPs had great scavenging effect on multiple ROS, such as hydroxyl radicals (•OH), superoxide radicals (O2•−) and hydrogen peroxide (H2O2). By observing the changes in morphology and mechanical properties of human umbilical vascular endothelium cells (HUVECs), it was further found that PBNPs could apparently alleviate the decrease of Young's modulus caused by oxidative stress damage and kept cells in their normal morphology. In addition, the distribution of F-actin revealed that the enhancement of cytoskeleton stability by PBNPs might be a key way to protect HUVECs from oxidative damage. Importantly, the antioxidant activities of PBNPs were found to be size-dependent, which indicated the smaller particle size had better antioxidant activities compared with the larger particle size. This study serves as a novel medium to reveal the mechanism of nanoparticles on cells at the single-cell level and demonstrates the great potential of atomic force microscopy in studying the application of nanoparticles in cell biology.

Iodine Gauche Effect Induced by an Intramolecular Hydrogen Bond.

The gauche conformer in 1-X,2-Y-disubstituted ethanes, that is, the staggered orientation in which X and Y are in closer contact, is only favored for relatively small substituents that do not give rise to large X···Y steric repulsion. For more diffuse substituents, weakly attractive orbital interactions between antiperiplanar bonds (i.e., hyperconjugation) cannot overrule the repulsive forces between X and Y. Our quantum chemical analyses of the rotational isomerism of XCH2CH2Y (X = F, OH; Y = I) at ZORA-BP86-D3(BJ)/QZ4P reveal that indeed the anti conformer is generally favored due to a less destabilizing I···F and I···O-H steric repulsion. The only case when the gauche conformer is preferred is when the hydroxyl hydrogen is oriented toward the iodine atom in the 2-iodoethanol. This is because of the significantly stabilizing covalent component of the I···H-O intramolecular hydrogen bond. Therefore, we show that strong intramolecular interactions can overcome the steric repulsion between bulky substituents in 1,2-disubstituted ethanes and cause the gauche effect. Our quantum chemical computations have guided nuclear magnetic resonance experiments that confirm the increase in the gauche population as X goes from F to OH.

A Ratiometric Photoacoustic Probe with a Reversible Response to Hydrogen Sulfide and Hydroxyl Radicals for Dynamic Imaging of Liver Inflammation

AbstractReversible imaging probes that allow for the dynamic visualization of the redox cycle between hydroxyl radical (⋅OH) and hydrogen sulfide (H2S) are vital to probe the redox imbalance‐involved pathological process in vivo. Herein, we report a reversible ratiometric photoacoustic (PA) imaging nanoprobe (1‐PAIN) for the real‐time imaging of ⋅OH/H2S redox cycle in vivo.1‐PAIN displays a low PA ratio between 690 and 825 nm (PA690/PA825), which significantly increases by ≈5‐fold upon oxidation by ⋅OH, and is switched back to the initially low PA690/PA825value upon reduction by H2S.1‐PAIN could dynamically report on the hepatic ⋅OH production in mice during the lipopolysaccharide (LPS)‐induced liver inflammation process, and visualize hepatic H2S generation during theN‐acetyl cysteine (NAC)‐induced anti‐inflammation process.1‐PAIN can act as a useful tool to probe the redox state in living biology, beneficial for the study of redox imbalance‐related diseases.

A Ratiometric Photoacoustic Probe with a Reversible Response to Hydrogen Sulfide and Hydroxyl Radicals for Dynamic Imaging of Liver Inflammation.

Reversible imaging probes that allow for the dynamic visualization of the redox cycle between hydroxyl radical (⋅OH) and hydrogen sulfide (H2 S) are vital to probe the redox imbalance-involved pathological process in vivo. Herein, we report a reversible ratiometric photoacoustic (PA) imaging nanoprobe (1-PAIN) for the real-time imaging of ⋅OH/H2 S redox cycle in vivo. 1-PAIN displays a low PA ratio between 690 and 825 nm (PA690 /PA825 ), which significantly increases by ≈5-fold upon oxidation by ⋅OH, and is switched back to the initially low PA690 /PA825 value upon reduction by H2 S. 1-PAIN could dynamically report on the hepatic ⋅OH production in mice during the lipopolysaccharide (LPS)-induced liver inflammation process, and visualize hepatic H2 S generation during the N-acetyl cysteine (NAC)-induced anti-inflammation process. 1-PAIN can act as a useful tool to probe the redox state in living biology, beneficial for the study of redox imbalance-related diseases.

Experimental research on spontaneous combustion of coal oxidized by ultraviolet photocatalysis

To study the effect of ultraviolet light on the spontaneous combustion characteristics of coal, Lijiahao long-flame coal was selected for irradiation treatment with a self-made ultraviolet light irradiation device. After irradiation for 0, 1, 2, 4, and 8 h, thermogravimetric experiments and Fourier transform infrared spectroscopy experiments were carried out. Compared with the raw coal, the dry cracking temperature, the ignition point temperature, and the maximum weight loss rate temperature of coal samples irradiated for 2 h by ultraviolet light were advanced to different degrees. The ignition activation energy was 0.62, 0.56, 0.59, and 0.91 times that of the raw coal after 1, 2, 4, and 8 h of ultraviolet light irradiation. The ultraviolet light irradiation accelerated the oxidation of –CH3, –CH2−, and –OH, resulting in enhanced coal activity. It shows that ultraviolet light irradiation has a promoting effect on the spontaneous combustion of coal, and the best promotion effect is observed when ultraviolet light is irradiated for 2 h. After 2 h of ultraviolet light irradiation, compared with the raw coal, the content of ether group in the coal structure decreased by 6.79%, the content of methyl and methylene in the benzene ring decreased by 8.68%, the content of C=O and carboxylic acid increased by 30.21%, the content of hydroxy ether and hydroxyl π hydrogen bond decreased by 14.94%, and the content of self-associating hydroxyl hydrogen bonds increased by 16.59%. It shows that ultraviolet light can destroy aromatic hydrocarbons in coal, catalyze the hydrolysis reaction of esters and ethers in coal to generate –OH and –COOH, and promote the oxidative spontaneous combustion of coal.

In‐situ Synthesis of Ionic Liquids on B‐doped Mesoporous SiO2 Catalyst for Epoxide‐CO2 Cycloaddition

AbstractA series of functionalized ionic liquids (ILs) immobilized on B‐doped mesoporous SiO2 catalysts were fabricated for effectively converting CO2 into cyclic carbonates under metal‐absent and cocatalyst‐free conditions. Functionalized imidazolium ILs were in‐situ synthesized by Debus‐Rdziszewski imidazole reaction. Among the prepared catalysts, 5B−SiO2−NH2−3−I catalyst owing to the synergistic effects of nucleophile, Lewis acid‐base and hydroxyl hydrogen bond donors in the catalyst, presented the better catalytic activity for propylene epoxide to the product of propylene carbonate with 99% yield and selectivity at 110 °C and 2 MPa CO2. The catalyst also displayed moderate yield for various mono‐substituent epoxides. Besides, the gradual decline in the product yield during consecutive runs could be easily refreshed by aqueous acidic solution washing.

Tide-Triggered Production of Reactive Oxygen Species in Coastal Soils.

We report an unrecognized, tidal source of reactive oxygen species (ROS). Using a newly developed ROS-trapping gel film, we observed hot spots for ROS generation within ∼2.5 mm of coastal surface soil. Kinetic analyses showed rapid production of hydroxyl radicals (•OH), superoxide (O2•-), and hydrogen peroxide (H2O2) upon a shift from high tide to low tide. The ROS production exhibited a distinct rhythmic fluctuation. The oscillations of the redox potential and dissolved oxygen concentration followed the same pattern as the •OH production, suggesting the alternating oxic-anoxic conditions as the main geochemical drive for ROS production. Nationwide coastal field investigations confirmed the widespread and sustainable production of ROS via tidal processes (22.1-117.4 μmol/m2/day), which was 5- to 36-fold more efficient than those via classical photochemical routes (1.5-7.6 μmol/m2/day). Analyses of soil physicochemical properties demonstrated that soil redox-metastable components such as redox-active iron minerals and organic matter played a key role in storing electrons at high tide and shuttling electrons to infiltrated oxygen at low tide for ROS production. Our work sheds light on a ubiquitous but previously overlooked tidal source of ROS, which may accelerate carbon and metal cycles as well as pollutant degradation in coastal soils.

1-hydroxy-6,6-Dimethyl-3-Phenyl-1,6-Dihydropyridine-2,5-Dione as a Promising Inhibitor of the SARS-CoV-2 Proteins: insight into the Crystal Structure, Hirshfeld Surface Analysis and Computational Study

In this work detailed studies of 1-hydroxy-6,6-dimethyl-3-phenyl-1,6-dihydropyridine-2,5-dione (1), which is of potential biological interest, are reported. The molecule of 1 is stabilized by O–H···O and two C–H···O hydrogen bonds. The former interaction yields a pseudo-aromatic hydrogen bonded five-membered ring. The overall crystal packing of 1 is mainly described by O–H···O hydrogen bonds and π···π interactions, yielding a 1D supramolecular ribbon-like chain. These chains are linked through weak C–H···O hydrogen bonds. The reciprocal favored intermolecular H···H/C/O and C···C contacts are main contributors to the total Hirshfeld surface of 1. The structure, electronic and optical properties of 1 were verified with the DFT calculations, which revealed that 1 is a strong electrophile with the most pronounced nucleophilic and electrophilic centers located on the carbonyl oxygen atoms and on the hydroxyl hydrogen atom, respectively. Values for the calculated polarizability and first-order hyperpolarizability parameters for a molecule of 1 are higher in comparison to those of urea. Bioavailability, druggability as well as absorption, distribution, metabolism, excretion and toxicity properties of 1 were evaluated using the SwissADME, BOILED-Egg and ProTox-II tools. It was established that for 1, the human blood-brain barrier penetration property is positive and gastrointestinal absorption property is high with the negative PGP effect on the molecule. Molecular docking was applied to examine the influence of this compound on a series of the SARS-CoV-2 proteins, of which 1 exhibits the best affinity behavior toward RdRp-RNA, nonstructural protein 14 (N7-MTase) and N protein (NCB site).

Spectroscopic and quantum mechanical study of a scavenger molecule: N,N-diethylhydroxylamine

We report a combination of quantum mechanical calculations and a range of spectroscopic measurements in the gas phase of N,N-diethylhydroxylamine, an important scavenger compound. Three conformers were observed by pulsed jet Fourier transform microwave spectroscopy in the 6.5–18.5 GHz frequency range. They are characterized by the hydroxyl hydrogen atom being in trans orientation with respect to the bisector of the CNC angle while the side alkyl chains can be both trans (global minimum, Cs symmetry, A = 7608.1078(4), B = 2020.2988(2) and C = 1760.5423(2) MHz) or one trans and the other gauche (second energy minimum, A = 5302.896(1), B = 2395.9822(4) and C = 1804.8567(3) MHz) or gauche’ (third energy minimum, A = 5960.8025(6), B = 2273.6627(4) and C = 1975.8074(4) MHz). For the global minimum, the 13Cα,13Cβ and 15N isotopologues were observed in natural abundance, allowing for an accurate partial structure determination. Moreover, several lines were detected by free jet absorption millimeter wave spectroscopy in the 59.6–74.4 GHz spectral range. The electron binding energies of the highest occupied molecular orbital and the next-to-highest occupied molecular orbital, determined by photoelectron spectroscopy, are 8.95 and 10.76 eV, respectively. Supporting calculations evidence that, (i) upon ionization of the HOMO, the molecular structure changes from an amine to an N-oxoammonium arrangement and (ii) the 0–0 of the HOMO-1 photoionization is 10.46 eV. The K-shell binding energies, determined by X-ray photoelectron spectroscopy, are 290.42 eV (Cβ), 291.45 eV (Cα), 405.98 eV (N) and 538.75 eV (O). The Fourier transform near infrared spectrum is reported and a tentative assignment is proposed. The equilibrium wavenumber (ω̃ = 3811 cm−1) and the anharmonicity constant (ω̃χ = −87.5 cm−1) of the hydroxyl stretching mode were estimated using a quadratic model.

A multi-target theranostic nano-composite against Alzheimer's disease fabricated by conjugating carbon dots and triple-functionalized human serum albumin

The complex pathogenesis of Alzheimer's disease (AD) involves the aggregation and accumulation of amyloid β-protein (Aβ) as well as elevated levels of reactive oxygen species (ROS), which requires the development of comprehensive diagnostic and therapeutic interventions. In this work, a multifunctional theranostic nano-composite (HSA-BFP@CDs) is constructed by conjugating triple-functionalized human serum albumin (HSA-BFP) as a theranostic agent targeting Aβ and carbon dots (CDs) as an ROS scavenger. HSA-BFP@CDs exhibits a fluorescence “off-on” effect at 700 nm upon interaction with Aβ aggregates, showing the capability for detection of Aβ plaques and potential for early diagnosis of AD. Besides, HSA-BFP@CDs effectively inhibits the aggregation of Aβ, increasing the viability of Aβ-treated cells from 74% to over 95% at 100 µg/mL. Moreover, multiple ROS, including hydroxyl radicals, superoxide radicals, hydrogen peroxide, and Aβ-Cu2+-induced-ROS, can be scavenged by HSA-BFP@CDs, thus resulting in the mitigation of cellular oxidative damages. Experiments with the AD model of Caenorhabditis elegans further demonstrate the multifunctionality of HSA-BFP@CDs in imaging amyloid plaques, reducing Aβ deposition, and relieving oxidative stress in vivo, showing the prospect for Aβ- and ROS-targeted AD diagnosis and treatment. This work provided new insight into the design of protein-carbon dots conjugate and the development of multi-target therapy of AD. Statement of significanceAlzheimer's disease (AD) is the most common form of dementia, which currently affects over 55 million people worldwide. Due to the complex pathogenesis of AD involving amyloid β-protein (Aβ) aggregation as well as elevated levels of reactive oxygen species (ROS), it is highly desired to develop comprehensive diagnostic and therapeutic interventions. In this paper, we fabricated a multifunctional theranostic nano-composite (HSA-BFP@CDs) via the conjugation of triple-functionalized human serum albumin (HSA-BFP) and carbon dots (CDs). The multifunctionality of HSA-BFP@CDs for efficient detection of Aβ aggregates and inhibition of Aβ aggregation as well as scavenging of ROS was demonstrated, demonstrating the potential of the protein-carbon dots conjugate for the multi-target therapy of AD.

Synthesis and anti-inflammatory activity of paeonol derivatives with etherized aryl urea by regulating TLR4/MyD88 signaling pathway in RAW264.7 cell

Thirty-three novel paeonol etherized aryl urea derivatives (PEUs) were synthesized via a bromination-Williamson Ether Synthesis-deprotection-nucleophilic addition reaction sequence. The structures of PEUs were characterized by LC-MS, HRMS, 1H NMR and 13C NMR spectra. The levels of nitric oxide (NO), tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages were initially employed to evaluate the anti-inflammatory effects of all compounds. Remarkably, b16 exhibited a good anti-inflammatory activity at 2.5 μm which is the same as the potency of paeonol at 20 μm. The results of mechanism research displayed that the anti-inflammatory effect of b16 was ascribed to the inhibition of the TLR4/MyD88 signaling pathway and inflammatory factors. Additionally, b16 distinctly reduced the generation of free radicals in macrophages and strikingly increased the mitochondrial membrane potential. According to the structure-activity relationships (SAR) of PEUs, the incorporation of halogens on the benzene ring and the hydrogen of phenol hydroxyl substituted by aryl urea, were beneficial to enhance the anti-inflammatory activities. Molecular docking results illustrated that the binding ability of b16 to TLR4 was stronger than that of paeonol. In summary, the novel aryl urea-derivied paeonol b16 could be a new promising candidate for the treatment of inflammation-related diseases.

Subcritical Water Enhanced with Deep Eutectic Solvent for Extracting Polysaccharides from Lentinus edodes and Their Antioxidant Activities.

In the present study, subcritical water extraction (SWE) assisted with deep eutectic solvent (DES) is used to extract Lentinus edodes polysaccharides (LEP). In addition, the antioxidant activity of the polysaccharide samples was also investigated. Based on a single factor test and response surface test, the optimal extraction factors were a liquid–solid solvent of 40:1 mL/g, extraction temperature of 147.23 °C, water content of 39.76% and extraction time of 17.58 min. Under these extraction conditions, the yield of LEP was 6.26 ± 0.08%. Compared with the SWE and hot water extraction (HWE), it improved by 19.24% and 17.01%, respectively. In addition, the results of monosaccharide composition, molecular weight, FT-IR, UV and SEM confirmed that the extracts had the features of polysaccharides. Interestingly, the polysaccharides obtained with the SWE assisted with the DES procedure showed a higher DPPH scavenging activity, hydroxyl radical scavenging activity and hydrogen peroxide scavenging activity, which indicated that the polysaccharides with this method had a stronger antioxidant activity. These findings demonstrated that the SWE-assisted DES is a strong method to obtain polysaccharides from Lentinus edodes for food, biopharmaceutical and other industrial production.

The process and mechanism for cesium and rubidium extraction with saponified 4-tert-butyl-2-(α-methylbenzyl) phenol

Cesium (Cs) and rubidium (Rb) separation from brine is an important and application-oriented topic. 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP) has been used for Cs and Rb extraction. However, the traditional extraction technology is base and acid consumed. In the present work, an innovative process for Cs and Rb extraction with t-BAMBP is developed, which consists of saponification, extraction, scrubbing and stripping. Both infrared spectrum and electrostatic potential analysis indicate the hydrogen of phenolic hydroxyl is dissociated from t-BAMBP during saponification and the oxygen of phenolic hydroxyl is the binding site for alkali metal ions. Saponified organic phase shows an excellent extraction effect for Cs+ and Rb+. The extraction reaches equilibrium in 5 min, with 99.5% Cs+ and 46.7% Rb+ are loaded into the organic phase in the single-stage extraction. Slope method indicates the structure of the extraction complex is MOR·3ROH (M = Cs+, Rb+, K+), where the electrostatic attraction between M+ and the oxygen of phenolic hydroxyl is dominant, and the cation–π interaction has a significant effect also. The extraction complex of MOR·3ROH dissociates in the acid environment while scrubbing and stripping is completed. The Cs+ and Rb+ are separated from the mixture phase, the proton H bonds to the phenolic hydroxyl group, and the extractant is regenerated.

Electrochemical Removal of Hydroxyl and Diffusible Hydrogen in Aluminum Fluoride Slags of Welding Flux-Cored Wires

Electrochemical Removal of Hydroxyl and Diffusible Hydrogen in Aluminum Fluoride Slags of Welding Flux-Cored Wires

Tracing the origin of heterogeneities in the local structure and very sluggish dynamics of [Cho][Gly] ionic liquid confined between rutile and graphite slit nanopores: A MD study

Atomistic-level understanding of the interfacial behavior of ionic liquids (ILs) confined in slit-like nanopores is of both fundamental and practical interest. Molecular dynamics (MD) is an efficient and robust approach to characterize the properties of confined systems in contrast with some limitations in direct experimental measurements at low-dimensions. In this research, MD simulations are used to study the biocompatible IL cholinium glycinate, [Cho][Gly], confined between two parallel plates of rutile or graphite, with the separation distance of 24 Å along the z-direction. As expected, both the microscopic local structure and dynamical behavior of the confined IL are very heterogeneous and depend effectively on the position of the ions to the pore walls. The ion z-density profile is used for segmentation of the inter-wall space into a central region and two outer layers. The behavior of ions in the central region is very similar to the bulk IL, while the behavior of the arranged ionic layers adjacent to the pore walls shows the clear deviation from the bulk IL due to confinement. In general, the confined IL shows a "solid-like" dynamics at T = 353K, especially in the outer layers near the walls as well as in the z-direction. The presence of the "IL-rutile wall" electrostatic interaction and hydrogen bonding (H-bonding) causes a significant difference in the local structure and very sluggish dynamics of the IL adjacent to the rutile walls vs the graphite walls. Simulation reveals a significant decrease in the average number of key cation-anion H-bonds at the outer layers relative to the central regions of both confined systems. The recognized [Cho]+⋯[Gly]-⋯[Cho]+ bridge structure at the central region is lost in the vicinity of the rutile walls due to inaccessibility of the hydroxyl hydrogen atom, which forms a stable H-bond with the rutile oxygen site. However, another unprecedented [Gly]- bridge is confirmed and preserved near the graphite walls, and [Cho]+ cations prefer to stay parallel to the wall surface to form the van der Waals dispersion interactions with the uncharged graphite walls.

Interaction of Cysteine with Li+ and LiF in the Presence of (H2O) n (n = 0-6) Clusters.

The interaction between cysteine with Li+ and LiF in the microcosmic water environment was investigated to elucidate how ions interact with amino acids and the cation–anion correlation effect involved. The structures of Cys·Li+(H2O)n and Cys·LiF(H2O)n (n = 0–6) were characterized using ab initio calculations. Our studies show that the water preferentially interacts with Li+/LiF. In Cys·Li+(H2O)0–6, Li+ interacts with amino nitrogen, carbonyl oxygen, and hydrophobic sulfur of Cys to form a tridentate mode, whereas in Cys·LiF(H2O)n, Li+ and F– work in cooperation and interact with carbonyl oxygen and hydroxyl hydrogen of Cys to form a bidentate type. The neutral and zwitterionic forms are essentially isoenergetic when the water number reaches three in the presence of Li+, whereas this occurs at four water molecules in the presence of LiF. Further research revealed that the interaction between Li+/LiF and Cys was mainly electrostatic, followed by dispersion, and the weakest interaction occurs at the transition from the neutral form to zwitterionic form. Natural population analysis charge analyses show that for Cys·Li+(H2O)n, the positive charge is mostly concentrated on Li+ except for the system containing three water molecules. For Cys·LiF(H2O)n, the positive charge is centered on the LiF unit in the range n = 0–6, and at n = 5, electron transfer from Cys to water occurs. Our study shows that the contribution of anions in zwitterionic state stabilization should be addressed more generally along with cations.

Two-body dissociation of formic acid following double ionization by ultrafast laser pulses

We studied the fragmentation of planar formic acid (HCOOH) molecules following their double ionization by intense ultrashort laser pulses. Deuterium tagging (i.e., HCOOD) combined with coincidence momentum imaging measurements of all fragment ions enabled determination of the role of the hydroxyl and carboxyl hydrogen atoms in the breakup. Specifically, we observe a strong preference for the hydroxyl (OD) group to remain intact in a ${\mathrm{HCOOD}}^{2+}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}{\mathrm{OD}}^{+}+{\mathrm{HCO}}^{+}$ fragmentation, which is an order of magnitude more likely than ${\mathrm{OH}}^{+}+{\mathrm{DCO}}^{+}$. An even larger preference for breaking the H-C bond over the O-H bond is observed in the ${\mathrm{H}}^{+}+{\mathrm{DCO}}_{2}^{+}$ and ${\mathrm{D}}^{+}+{\mathrm{HCO}}_{2}^{+}$ deprotonation channels. Bond rearrangement, leading to ${\mathrm{H}}_{2}^{+}$ or ${\mathrm{H}}_{2}{\mathrm{O}}^{+}$ formation, exhibits no isotopic preference. The kinetic-energy-release distributions of the ${\mathrm{OH}}^{+}+{\mathrm{DCO}}^{+}$ and ${\mathrm{O}}^{+}+{\mathrm{H}}_{2}{\mathrm{CO}}^{+}$ breakup channels suggest that more than one process contributes to these final products, although further theoretical work is needed to identify the specific paths.

Novel insights into the mechanism for protic solvent promoting Pd/C-catalyzed hydrodechlorination of chlorinated organic compounds

• Protic solvents promoted catalytic HDC of 4-CBP with Et 3 N over Pd/C catalyst. • HDC rate of 4-CBP increased with increase of water content in mixed solvent systems. • Mechanism for protic solvents promoting Pd/C-catalyzed HDC reactions was elucidated. • Protic solvents participated in Pd/C-catalyzed HDC and hydrogenation reactions. Solvent effects in liquid-phase hydrodechlorination (HDC) of chlorinated organic compounds (COCs) over Pd/C catalyst were systematically studied. For the HDC of 4-chlorobiphenyl (4-CBP) with triethylamine (Et 3 N), Pd/C exhibited much higher catalytic activity in protic solvents than that in aprotic polar and non-polar solvents, and a clear correlation between the HDC rate and polarity of protic solvents was observed. Moreover, water promoted Pd/C-catalyzed HDC of 4-CBP in homogeneous alcohol-water solvents and biphasic organic-water solvents with Et 3 N, and the HDC rate of 4-CBP increased with the increase of water content in the above solvent systems. Catalyst characterization (FT-IR and XRD) combined with solvent parameters and isotope labelling analysis were introduced to explain in-depth the solvent effects in the HDC of 4-CBP with Et 3 N. It was found that protic solvents would transfer active hydrogen atom (H*) via hydrogen bonding network or exchange their hydroxyl hydrogen with H*, which was beneficial to the stabilization of H* and interface HDC reaction. Thus, the higher HDC rate was achieved in solvent systems contained protic solvents with higher hydrogen-bond donor capability ( α ) values. On the other hand, non-polar and polar aprotic solvents had a negative effect on H* and mass transfer, and thus suppressed interface HDC reaction. Similar solvent effects were observed in Pd/C-catalyzed hydrogenation of unsaturated bonds-containing groups (nitryl group, carbonyl group, and carbon-carbon double bond). The results presented here would provide vital guidance for the rational selection of solvent systems for Pd/C-catalyzed HDC of COCs and hydrogenation of unsaturated bonds-containing groups.