Reaction Fragment Research Articles

Two‐Electron Oxidative Atom and Group Transfer Reactions at a Well‐Defined Uranium(II) Center

The multi‐electron redox chemistry of uranium(II) compounds remains largely unexplored. Herein, we report a series of two‐electron oxidative atom and group transfer reactions at a well‐defined uranium(II) center. The reactions of uranium(II) complexes [M][(AdTPBN3)U] (M = K(2,2,2‐cryptand) and K(18‐crown‐6)(THF)) with pyridine‐N‐oxide or nitrosobenzene, elemental sulfur/selenium or triphenylphosphine sulfide/selenide, and ditellurium salt led to the isolation of uranium(IV) terminal oxo and chalcogenido complexes [M][(AdTPBN3)UX] (X = O, S, Se, Te). In addition, the reactions of [M][(AdTPBN3)U] with aryl azides ArN3 or diazoalkanes R2CN2 quantitatively yielded uranium(IV) terminal imido [M][(AdTPBN3)UNAr] or hydrazonido(2–) complexes [M][(AdTPBN3)UN2CR2], respectively. Notably, the low‐temperature reaction between [M][(AdTPBN3)U] and mesityl azide allowed the isolation of the first uranium(IV) aryldiazenylimido complex as an intermediate. These uranium(IV)–element multiply bound compounds were fully characterized by X‐ray crystallography, 1H NMR spectroscopy, absorption spectroscopy, solution magnetic susceptibility, and elemental analysis. The controlled two‐electron oxidative reactions at a uranium(II) center not only expand the redox reactivity of uranium(II) but also offer a convenient new route to access uranium–element multiply bound compounds.

Two-Electron Oxidative Atom and Group Transfer Reactions at a Well-Defined Uranium(II) Center.

The multi-electron redox chemistry of uranium(II) compounds remains largely unexplored. Herein, we report a series of two-electron oxidative atom and group transfer reactions at a well-defined uranium(II) center. The reactions of uranium(II) complexes [M][(AdTPBN3)U] (M = K(2,2,2-cryptand) and K(18-crown-6)(THF)) with pyridine-N-oxide or nitrosobenzene, elemental sulfur/selenium or triphenylphosphine sulfide/selenide, and ditellurium salt led to the isolation of uranium(IV) terminal oxo and chalcogenido complexes [M][(AdTPBN3)UX] (X = O, S, Se, Te). In addition, the reactions of [M][(AdTPBN3)U] with aryl azides ArN3 or diazoalkanes R2CN2 quantitatively yielded uranium(IV) terminal imido [M][(AdTPBN3)UNAr] or hydrazonido(2-) complexes [M][(AdTPBN3)UN2CR2], respectively. Notably, the low-temperature reaction between [M][(AdTPBN3)U] and mesityl azide allowed the isolation of the first uranium(IV) aryldiazenylimido complex as an intermediate. These uranium(IV)-element multiply bound compounds were fully characterized by X-ray crystallography, 1H NMR spectroscopy, absorption spectroscopy, solution magnetic susceptibility, and elemental analysis. The controlled two-electron oxidative reactions at a uranium(II) center not only expand the redox reactivity of uranium(II) but also offer a convenient new route to access uranium-element multiply bound compounds.

Plasmochemical and Reactive Ion Etching of Gallium Arsenide in Difluorodichloromethane with Helium

The kinetics of interaction of high-frequency plasma of difluorodichloromethane and its mixture with helium with the surface of gallium arsenide was experimentally studied. It was established that in the studied range of conditions, complete decomposition of the original difluorodichloromethane molecule to atomic carbon occurs. It has been confirmed that the main chemically active particles responsible for etching are reactive chlorine atoms. It has been shown that the etching process occurs in the mode of an ion-stimulated chemical reaction, where the desorption of products under the influence of ion bombardment plays a significant role in surface cleaning. The emission spectra of plasma radiation in the presence of a gallium arsenide semiconductor wafer are analyzed. Control lines and stripes were selected to control the speed of the etching process based on the emission intensity of the lines and stripes of the etching products.

Tailor‐Made Buffer Materials: Advancing Uniformity and Stability in Perovskite Solar Cells

AbstractAlong with the growing popularity of the p‐i‐n structure, bathocuproine (BCP) is increasingly recognized as a crucial buffer layer between the electron transport layer and electrode with the role of mitigating Schottky contact and enhancing performance. However, the chemical structure and role of its functional groups have not been thoroughly elucidated. This study introduces a novel modification of BCP in perovskite solar cells (PSCs) by altering functional groups to optimize their geometrical molecular structures and electronic properties. The substitution of aromatic phenyl and p‐tolyl groups to 2,9‐position on the BCP is highly effective in increasing the planarity of the conjugated backbone and protecting the reactive nitrogen atoms of the phenanthroline core, thereby improving charge transport and device stability. Experimental analyses, including electrostatic force microscopy, impedance spectroscopy, and photoluminescence, reveal that the modified BCP significantly enhances charge transport, reduces recombination losses, and markedly improves the structural stability of PSCs, leading to prolonged device lifetimes. The findings highlight the potential of structurally optimized BCP derivatives as a critical component in advancing high‐efficiency and durable PSCs.

Unique Applications of para-Hydrogen Matrix Isolation to Spectroscopy and Astrochemistry.

Cryogenic solid para-hydrogen (p-H2) exhibits pronounced quantum effects, enabling unique experiments that are typically not possible in noble-gas matrices. The diminished cage effect facilitates the production of free radicals via in situ photolysis or photoinduced reactions. Electron bombardment during deposition readily produces protonated and hydrogenated species, such as polycyclic aromatic hydrocarbons, that are important in astrochemistry. In addition, quantum diffusion delocalizes hydrogen atoms in solid p-H2, allowing efficient H atom reactions with astrochemical species and introducing new concepts in astrochemical models. Some H atom reactions display anomalous temperature behaviors, highlighting the rich chemistry in p-H2. The investigation on quantum diffusion of heavier atoms and molecules is also important for our understanding of the chemistry in interstellar ice. Additionally, matrix shifts of electronic transitions of polycyclic aromatic hydrocarbons in p-H2 are less divergent than those in solid Ne such that systematic measurements in p-H2 might help in the assignment of diffuse interstellar bands.

Atmospheric Pressure Photoionization with Halogen Anion Attachment for Mass Spectrometric Analysis of Hydrocarbons and Hydrocarbon-Based Polymers.

Aliphatic hydrocarbons and hydrocarbon-based synthetic polymers are of interest in many fields, but their characterization by mass spectrometric methods is generally limited due to their poor ionizability. Recently, atmospheric pressure photoionization (APPI), combined with halogen anion attachment in negative-ion mode, has drawn attention as a potential method for ionizing various polymers without extensive fragmentation or other unwanted side reactions. In this work, the applicability of halogen anion attachment with APPI was studied using several synthetic polymers, including polyethylene, polypropylene, polyisoprene, and polystyrene, as well as simple n-alkanes of various chain lengths. For hydrocarbon-based polymers, the method produced clear distributions of intact polymer adduct ions when different halogen anions were used. It was found that increasing the halogen anion size decreased ionization efficiency, particularly in the absence of π-bonds in the polymer structure. Testing with simple n-alkanes showed that only molecules containing fifty or more carbon atoms formed detectable halogen adducts, possibly due to the low gas-phase stabilities of the lighter n-alkane adduct ions. In conclusion, halogen anion attachment with negative-ion APPI appears to be a highly promising method for polymer analysis, providing structural data and clean polymer mass spectra with minimal fragmentation, which can be useful for the identification of unknown samples.

Measurements of the Reaction Rate Coefficients of Atomic Hydrogen with Astrochemical Anions: CN− and C3N−

We present the temperature-dependent reaction rate coefficients of CN− and C3N− with atomic hydrogen in the temperature range from 7 to 290 K, measured in a 16-pole radio-frequency ion trap. The rate of C3N− with H steadily increases toward lower temperatures, while the rate coefficients for the CN− + H system show a sudden change around 160 K. Fits to the data were performed to determine temperature-dependent reaction rate coefficients. The fits reveal a rate coefficient of 4.1(3)×10−10(T/300)−0.31(6) cm3 s−1 for C3N− + H. For CN−, we determined a rate coefficient for the temperature regime below 160 K of 3.2(4)×10−10(T/300)−0.31(11) cm3 s−1. Given our present results, higher rate coefficients than previously reported must be assumed for the modeling of cold interstellar environments involving these H atom reactions.

Toxicological and environmental risks of enalapril and their possible transformation products generated under phototransformation reactions

Pharmaceutical active compounds (PACs) in the concentration range of hundreds of ng/L to μg/L have been identified in urban surface water, groundwater, and agricultural land where they cause various health risks. These pollutants are classified as emerging and cannot be efficiently removed by conventional wastewater treatment processes. The use of nano-enabled photocatalysts in the removal of pharmaceuticals in aquatic systems has recently received research attention owing to their enhanced properties and effectiveness. In the current study, toxicological and environmental risks of enalapril (ENL) and their possible transformation products (TPs) generated under phototransformation processes (e.g., photolysis and photocatalysis reactions) were assessed. In photolysis reaction, removal of ENL was incomplete (< 16 %), while mineralization degree was negligible. In contrast, total removal of ENL was achieved through the photocatalytic process and its maximum mineralization ratio was 66 % by using natural radiation. Proposed transformation pathways during the phototransformation of ENL include hydroxylation and fragmentation reactions generating transformation products (TPs) such as hydroxylated TPs (m/z 393) and enalaprilat (m/z 349). Potential environmental risks for aquatic organisms were not observed in the concentrations of both ENL and enalaprilat contained in surface water. However, the acute and chronic toxicities prediction of TPs such as m/z 409, 363, and 345 showed toxic effects on aquatic organisms. Thus, more studies regarding TPs monitoring for both ENL and PhACs with the highest occurrence worldwide are necessary for the creation of a database of the concentrations contained in surface water and groundwater for the assessment of the potential environmental risk for aquatic organisms.

BODIPY Compounds Substituted on Boron.

BODIPY compounds are important organic dyes with exceptional spectral and photophysical properties and numerous applications in different scientific fields. Their widespread applications have flourished due to their easy structural modifications, which enable the preparation of different molecular structures with tunable spectral and photophysical properties. To date, researchers have mostly devoted their efforts to modifying BODIPY meso-position or pyrrole rings, whereas the substitution of fluorine atoms remains largely unexplored. However, chemistry of the boron atom is possible, and it enables tuning of the photophysical properties of the dyes, without tackling their spectral properties. Furthermore, modifications of boron affect the solubility and aggregation propensity of the molecules. This review article highlights methods for the preparation of 4-substituted compounds and the most important reactions on the boron of the BODIPY dyes. They were divided into reactions promoted by Lewis acid (AlCl3 or BCl3), or bases such as alkoxides and organometallic reagents. By using these two methodologies, it is possible to cleave B-F bonds and substitute them with B-C, B-N, or B-O bonds from different nucleophiles. A special emphasis in this review is given to still underdeveloped photochemical reactions of the boron atom of BODIPY dyes. These reactions have the potential to be used in the development of a new line of BODIPY photo-cleavable protective groups (also known as photocages) with bio-medicinal and photo-pharmacological applications, such as drug delivery.

Association of 25(OH)-Vitamin D3 Serum Concentrations and Vitamin D Receptor Gene Variants with the Risk of Idiopathic Spontaneous Preterm Birth in the Croatian Population.

Preterm birth (PTB) forms a heterogeneous group with possible genetic predisposition. 25(OH)-vitamin D3 plays a significant role during implantation, placentation, and the maintenance of normal pregnancy. The aim of our research was to examine whether FokI, Cdx2, and ApaI VDR gene variants, as well as serum concentrations of 25-hydroxy25(OH)-vitamin D3 in women and their newborns, might be predisposing factors for idiopathic spontaneous preterm birth. The patient group consisted of 44 pairs of women with ISPTB and their children, and the control group consisted of 44 pairs of women who delivered at term and their children. At the time of delivery, peripheral blood was collected from every woman, and after newborn delivery, umbilical cord blood was collected. For genotyping of the rs2228570 C/T, rs11568820 G/A, and rs7975232 T/G SNPs, a combination of polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) was used. Serum concentrations of 25(OH)-vitamin D3 were determined using high-performance liquid chromatography (HPLC). There were no statistically significant differences in the frequencies of VDR genotypes and alleles between women with ISPTB and control women. There was a statistically significant difference in the distribution of VDR Cdx-2 (rs11568820) genotypes between preterm-born children and controls, with the GG genotype and G allele being more prevalent among patients than controls (p < 0.001). There were no statistically significant differences in mean values between women with ISPTB and control women, nor between preterm and full-term newborns, although the 25(OH)-vitamin D3 concentrations in preterm-born children were lower than in controls. Furthermore, there was a statistically significant correlation in 25(OH)-vitamin D3 concentrations between mothers and children both in the patient and in the control groups (b = 0.771, p < 0.001). The results of our study demonstrate a notable association between the VDR Cdx2 gene polymorphism and idiopathic spontaneous preterm birth (ISPTB) in a Caucasian population, but because of the small number of participants, further research is needed.

Semitransparent Cu2O Films Based on CuO Back Layer for Photoelectrochemical Water Splitting and Photovoltaic Applications.

Cuprous oxide (Cu2O) as an intrinsic p-type semiconductor is promising for solar energy conversion. The major challenge in fabricating Cu2O lies in achieving both high transparency and high performance in a tandem device. The Cu2O photocathodes often employ gold as the back contact layer. However, it is not an optimal choice in tandem device due to its poor transmission, scarcity, and electron-hole recombination at the interface of Au and Cu2O. Here, we presented a facile method that utilizes the earth-abundant material copper oxide (CuO) to fabricate highly transparent Cu2O devices. The maximum transmittance of the Cu2O film on CuO (FTO/CuO/Cu2O) increased from 42 % to 58 % compared with Cu2O film on Au (FTO/Au (3 nm)/Cu2O) in 550-800 nm. After coating atomic layer deposition (ALD) layers and hydrogen evolution reaction (HER) catalyst, the photocurrent density at 0 V (versus RHE) of the semitransparent Cu2O photocathode with CuO as the back layer for photoelectrochemical (PEC) water splitting reached -4.9 mA cm-2, which showed a 24.5 % improvement compared with FTO/Au/Cu2O photocathode. Moreover, expanding the CuO layer strategy to the field of solar cells enables Cu2O solar cells to achieve a PCE of 2.37 %.

The Relationship Between miR-196a2 Polymorphism and Colorectal Cancer Risk

ABSTRACT Objective MicroRNAs are small endogenous, non-coding, single-stranded posttranscriptional RNA molecules. The discovery of microRNAs has made new contributions to cancer diagnosis and treatment. These microRNAs reported as a responsible for colorectal cancer development with several epigenetic changes. In this study, it was aimed to evaluate the relationship between the polymorphism of miR-196a-2 polymorphism rs11614913 and colorectal cancer in Turkish population. Methods Two hundred colorectal cancer patient (124 colon cancer and 76 rectal cancer) and 240 health control individuals were included in our study, which was planned as a hospital based retrospective cohort study. MiR-196a2 polymorphism in peripheral blood samples has been determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) method. Significance of the results has been evaluated by using SPSS (20.0 SPSS Inc., Chicago, IL, USA.) statistical program. Results miR-196a2 C / C + C / T genotypes was found to be associated with the risk of colorectal cancer development (p: 0.001; OR: 2.04, 95% CI: 1.293-3.236). The subgroup analysis, showed that the C / C + C / T genotype increased the risk of colon cancer development 2.11 times (p: 0.016; 95% CI: 1.136-3.918) and rectal cancer 2.86 times (p: 0.011; 95% CI:1.242-6.592). The relationship between any clinicopathological features of colorectal cancer and the frequency of the C / C + C / T genotype of miR196a2 was not statistically significant (p&gt; 0.05). Conclusion This study supports that miR-196a2's C / C + C / T genotypes is related with increased colorectal cancer development risk.

Reaction of F Atoms with Carbonyl Sulfide: Experimental and Theoretical Study.

The gas phase reaction of fluorine atoms with carbonyl sulfide, F + OCS → SF + CO (1), has been investigated over a wide temperature range, T = 220-960 K, in a discharge-flow system combined with mass spectrometry for the analysis of the reactive mixture. The reaction rate coefficient was determined as a function of temperature using both absolute (under pseudo-first-order conditions using an excess of F atoms) and relative rate methods: k1 = (8.95 ± 0.52) × 10-11 exp((102 ± 20)/T) cm3 molecule-1 s-1 (with an estimated total uncertainty of 15% independent of temperature). The SF radical was observed as the main primary reaction product. The experimental results are supported by theoretical calculations, which evidence that the reaction is exothermic with a weak negative temperature dependence.

Constructing Targeted Strong Nb4d-O2p-Li2s Configurations to Obtain Excellent Energy Density and Long Life for Li-Rich Cathodes.

The Li-rich Mn-based cathode materials (LMRs) deliver excellent energy density and exhibit low cost, which are considered as the most promising cathode materials for the next generation lithium-ion batteries. However, the irreversible redox reaction of the oxygen atoms directly leads to release oxygen and intensifies phase transformation. Besides, the local stress and strain will be generated due to the unit-cell volume difference between R-3m and C2/m phases, which continuously aggravates the collapse of secondary particles. Herein, the strong Nb4d-O2p-Li2s configurations at the Li1 sites of the TM-layer in the C2/m phase and secondary particles with the radial arrangement of refined primary particles are designed to inhibit oxygen release and relieve lattice stress by Nb2O5 treatment. Meanwhile, the preferential growth of the active {010} planes is presented to obtain an excellent transmission rate of Li+. As a result, the designed LMR delivers remarkable electrochemical properties with high discharge capacity and initial coulomb efficiency of 276 mAh g-1 and 85 % at 0.1 C, outstanding cycling retention rate of 81 % after 300 cycles. This novel crystal structure combining oxygen coordination regulation and micro-nano scale design provides inspiration for the design of high-performance LMRs.

Constructing Targeted Strong Nb4d−O2p−Li2s Configurations to Obtain Excellent Energy Density and Long Life for Li‐Rich Cathodes

AbstractThe Li‐rich Mn‐based cathode materials (LMRs) deliver excellent energy density and exhibit low cost, which are considered as the most promising cathode materials for the next generation lithium‐ion batteries. However, the irreversible redox reaction of the oxygen atoms directly leads to release oxygen and intensifies phase transformation. Besides, the local stress and strain will be generated due to the unit‐cell volume difference between R‐3m and C2/m phases, which continuously aggravates the collapse of secondary particles. Herein, the strong Nb4d−O2p−Li2s configurations at the Li1 sites of the TM‐layer in the C2/m phase and secondary particles with the radial arrangement of refined primary particles are designed to inhibit oxygen release and relieve lattice stress by Nb2O5 treatment. Meanwhile, the preferential growth of the active {010} planes is presented to obtain an excellent transmission rate of Li+. As a result, the designed LMR delivers remarkable electrochemical properties with high discharge capacity and initial coulomb efficiency of 276 mAh g−1 and 85 % at 0.1 C, outstanding cycling retention rate of 81 % after 300 cycles. This novel crystal structure combining oxygen coordination regulation and micro‐nano scale design provides inspiration for the design of high‐performance LMRs.

Synthesis, spectroscopy, solvation effect, topology and molecular docking studies on 2,2′-((1,2 phenylenebis (azaneylylidene)) bis (methaneylylidene)) bis(4-bromophenol)

The 2,2′-((1,2 phenylenebis (azaneylylidene)) bis (methaneylylidene)) bis(4-bromophenol) (5BSOP) Schiff base was synthesized, characterized using different spectroscopic techniques, and the data are compared with predictions from DFT computations. The calculated energy values are -8.65 eV (HOMO) and -6.66 eV (LUMO), and the energy gap was found to be 1.99 eV. The reactive atom sites in the chemical are identified by MEP analysis. The locations of localized and delocalized orbitals are revealed through ELF and LOL surface maps. The sites of non-covalent interactions are exposed by RDG and NCI analysis. The possible inter and intra-molecular interactions were determined by NBO analysis and the highest stabilization energy observed was 40.07 kcal/mol. Biological performance as a HMGCS2 expression enhancer was predicted by Pass online studies. Molecular docking simulation with protein 706I having HMGCS2 expression inhibition characteristics revealed a stable receptor-ligand interaction pose at a binding energy of -4.74 kcal/mol. The interaction of the Phe61 amino acid chain of 706I with 5BSOP through conventional H-bond expressed a bond distance of 3.24 Å.

Electron Transfer Capability in Atomic Hydrogen Reactions for Imidazole Groups Bound to the Insulating Alkanethiolate Layer on Au(111).

The charge transfer capability associated with chemical reactions at metal-organic interfaces was studied via the atomic H addition reaction for an imidazole-terminated alkanethiolate self-assembled monolayer (Im-SAM) film on Au(111) at room temperature, using near-edge X-ray absorption fine structure spectroscopy, infrared reflection absorption spectroscopy, work function measurements, and density functional theory calculations. The imidazolium cation is a stable species in liquids; therefore, it is pertinent to determine whether the hydrogenation reactions of the imidazole groups produce imidazolium cations accompanied by electron transfer to the Au substrate, even in the absence of solvate and/or counterions on the insulating alkanethiolate layer. The experiments made it clear that the imidazolium moieties were formed during the irradiation of Im-SAM with atomic H. Theoretical model calculations also revealed that the total energies and molecular orbital levels satisfied the imidazolium cation formation associated with electron transfer. In a detailed analysis of the work function change depending on H irradiation, we confirmed that some of the imidazolium radicals became cations in Im-SAM.

Production of neutron-rich nuclei in the vicinity of 78Ni: Fragmentation reactions of unstable 81Ga and 82Ge beams

The fragmentation reactions of neutron-rich unstable nuclei 81Ga and 82Ge at 250 MeV/nucleon have been studied in order to search the optimal mean for the production of very neutron-rich nuclei in the vicinity of 78Ni. The newly measured cross sections were compared with various calculations, showing a good agreement with EPAX3.01. The present work provides experimental insights into the two-step scheme—fragmentation following fission—as a method to produce very neutron-rich nuclei through a combination of ISOL and fragmentation of post-accelerated beams of unstable nuclei. Our results enable an evaluation of the potential of the two-step scheme in the production of very neutron-rich nuclei for the 78Ni region. The two-step scheme using fragmentation of a post-accelerated 81Ga beam could be an option to produce neutron-rich nuclei around 78Ni when the 81Ga beam intensity reaches 1.0×108 pps, compared to the one-step scheme with fission of 238U.

A Two-Phase Hydrogenation Membrane for Contaminants Reduction at High Hydrogen Reagent Utilization Efficiency.

Heterogeneous hydrogenation is surging as a promising strategy for selective removal of water pollutants, yet numerous efforts rely on catalyst design to advance catalytic activity. Herein, we enhanced the mass transfer and the utilization of hydrogen reagent through construction of a two-phase flow-through membrane reaction device (Pd/SiC-MR). Pd/SiC-MR displays high efficiency and selectivity toward removal of multiple pollutants. For instance, rapid (∼0.35 s) and exclusive hydrogenation (>99%) of carbon-chlorine bond in organohalogens were realized at high water flux (220 L/m2/h). More importantly, the two-phase Pd/SiC-MR reaction system achieved 31.4% utilization of hydrogen reagent, 1-3 orders of magnitude higher than those by classical slurry or fixed-bed reactor. The high hydrogenation performance is attributed to the close proximity of the hydrogen source, reactive hydrogen atom, and pollutant under high molecular collision frequency in membrane pores. Our study opens an approach for improved hydrogen reagent utilization while reserving the high pollutant removal efficiency through altering operating conditions, beyond complex material design limitations in hydrogenation water purification.

Investigation of the reaction of hydrogen iodide with a chlorine atom in the atmosphere above the sea

By the method of resonant fluorescence (RF) of chlorine atoms and iodine atoms, the rate constant of the reaction of a chlorine atom with hydrogen iodide at a temperature of 298 K. The values of the reaction constants measured by both methods turned out to be quite close. The role of this reaction in the chemistry of the troposphere above the surface of the oceans is discussed.