Reaction Of Bis Research Articles

Synthesis, characterization, crystal structures and biological activity of molybdenum complexes derived from bis(acetylacetonato)dioxomolybdenum(VI) and Schiff bases

Reaction of bis(acetylacetonato)dioxomolybdenum(VI) with 4-fluoro-2-((pyridin-2-ylmethylene)amino)phenol and 3-methyl-2-((pyridin-2-ylmethylene)amino)phenol, respectively in methanol afforded two new molybdenum complexes [MoO2L1] and [MoO2L2], where L1 and L2 are the dianionic form of 3-(((5-fluoro-2-hydroxyphenyl)amino)(pyridin-2-yl)methyl)pentane-2,4-dione (H2L1) and 3-(((2-hydroxy-6-methylphenyl)amino)(pyridin-2-yl)methyl)pentane-2,4-dione (H2L2). Both complexes have been characterized by elemental analysis, IR, UV–Vis, 1H and 13C NMR spectra. Molecular structures of the complexes have been determined by X-ray crystallography. In the complexes, the ligands coordinated to the Mo atoms via pyridine nitrogen, amino nitrogen, phenolate oxygen, and enolate oxygen atoms. The octahedral coordination of the Mo atoms is furnished by two oxido oxygen atoms. The complexes were evaluated for their antibacterial activities on Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescens, and antifungal activities on Candida albicans and Aspergillus niger, and gave interesting results.

Τheoretical study of the 13C + d system, in the framework of the R-Matrix model

In the present work, a theoretical study of the 13C + d system is carried out in the framework of the R-Matrix model. The experimental data used were taken from the IBANDL library. The cross-section measurements for the reactions have been carried out in the energy range of 0.49-1.65 MeV for three backscattering angles of 135°, 150° and 165°. The R-Matrix calculations were performed with the use of the AZURE2 code and involved the simultaneous analysis of the 13C (d, p0)14C, 13C (d, t0)12C 13C (d, a0)11B, 13C(d,a1)11B reaction channels with one, coherent set of parameters.

Reactions of bis(trifluoromethyl)-substituted 2-azanorbornenes and 2-azanorbornanes: electrophilic addition, N-substitution, and hydrogenation

Reactions of bis(trifluoromethyl)-substituted 2-azanorbornenes and 2-azanorbornanes: electrophilic addition, N-substitution, and hydrogenation

Thermal diffusion of lithium implanted in small and large grain boron carbide

Boron carbide (B4C) is used as a neutron absorber for nuclear reactor control and installation protection in most types of reactors. When the B4C is irradiated in the reactor, large quantities of lithium and helium (up to about 1022 /cm3) are produced due to the neutron absorption reaction 10B (n, α) 7Li. This work aims at studying the Li diffusion in large grain size (20–50 µm) or small grain size (0.2 – 5 µm) B4C in the temperature range of 500–800 °C. Lithium was implanted in B4C samples at a fluence of 1014 ions/cm2 (maximum concentration of 54 at. ppm). The Li concentration profiles as a function of depth were obtained before and after each heat treatment by Time-Of-Flight Secondary Ionization Mass Spectrometry technique. A heterogeneous diffusion process was observed depending on the implantation depth. Considering diffusion in the non-damaged, bulk material beyond the implanted zone, the thermal diffusion of lithium into the grain boundaries was found to be about four orders of magnitude higher than into the grains.

Particle and Heavy Ion Transport Code System‐Based Microdosimetry for the Development of Boron Agents for Boron Neutron Capture Therapy

AbstractBoron neutron capture therapy (BNCT) is a radiation therapy that selectively kills cancer cells at the cellular level using the boron neutron capture reaction (BNCR) (10B(n.α)7Li). The amount of boron 10B delivers in boronophenylalanine (BPA)‐BNCT to achieve anti‐tumor effects is ≈15–40 ppm. The same is true for all boron drugs; however, whether the same amount of 10B is required for other boron drugs with different accumulation characteristics has not been intensively investigated. Therefore, herein, a virtual cell model with intracellular organelles is prepared, and the BPA equivalent dose concentration to the cell nucleus is analyzed using particle and heavy ion transport code system‐based microdosimetry. Additionally, the intranuclear minimal region (IMR) is set as a reference for the concept of the intranuclear domain in the microdosimetric kinetic model, and the BPA equivalent dose concentration to the IMR is estimated. The required boron delivery dose greatly varies depending on the dose assessment based on the accumulation characteristics of boron agents in intracellular organelles. Evaluation of the BNCR effect according to the accumulation characteristics without being influenced by the specified value of 15–40 ppm is recommended.

Differential cross-section measurements of the 11B(d, pγ1,2)12B reactions for analytical applications

In the present work, the 11B(d, pγ)12B differential cross-sections for gamma- rays originating from the first two excited states of the 12B at 953 and 1674 keV were measured in the energy range Ed,lab = 671–1990 keV with steps of 30 or 40 keV at a detection angle of 90°. The target was a thin natB2O3 film evaporated onto a self-supporting Ag layer. The thick target gamma-ray yields were measured in the same experimental setup using a pressed pellet made of natB powder. The obtained results were compared with the existing data in literature. The validity of measured cross-sections was checked through a thick target benchmarking experiment.

Anticancer activity and DNA interaction of bis(pyridyl)allene-derived metal complexes

Abstract The constant need for novel drugs has prompted the scientific community to explore alternative structures to natural products and small and medium size organic compounds used in classic medicinal and pharmaceutical chemistry. Since the discovery of cisplatin, organometallic compounds have revealed great potential as metallodrugs and their development has exponentially grown in recent years. In this manuscript, we describe our efforts towards the synthesis of new metallodrugs by reaction of bis(pyridyl)allenes and metal complexes. Two classes of compounds are presented: one in which the allene structure is intact and the metal (Pd(II), Pt(IV) or Au(III)) coordinates to the pyridine-nitrogens; and another, in which one of the pyridines cyclises into a gold-activated allene to form β-N-stabilised gold carbenes. Both classes of compounds are active catalysts in important organic reactions, and are also promising antimicrobial, antifungal and anticancer agents. In this work, we describe the promising anticancer activity, against breast cancer cells, of the gold carbene complexes, and preliminary studies of their interaction with DNA, including non-canonical DNA structures. Our results have revealed an unusual selective stabilisation of hTeloC i-motif by one of the Au(III) carbene complexes, that opens up exciting opportunities for further development of novel DNA-binding metallodrugs.

Detection of limited-energy α particles using CR-39 in laser-induced p −11B reaction

Due to the harsh radiation environment produced by strong laser plasma, most of the detectors based on semiconductors cannot perform well. So, it is important to develop new detecting techniques with higher detection thresholds and highly charged particle resolution for investigating nuclear fusion reactions in laser-plasma environments. The Columbia Resin No. 39 (CR-39) detector is mainly sensitive to ions and insensitive to the backgrounds, such as electrons and photons. The detector has been widely used to detect charged particles in laser-plasma environments. In this work, we used a potassium–ethanol–water (PEW) etching solution to reduce the proton sensitivity of CR-39, by raising the detection threshold for the research of laser-induced 11B(p, α)2α reaction. We calibrated the 3–5 MeV α particles in an etching condition of 60°C PEW-25 solution (17% KOH + 25%C2H5OH + 58%H2O) and compared them with the manufacturer’s recommended etching conditions of 6.25 N NaOH aqueous solution at 98°C in our laser-induced nuclear reaction experiment. The results indicate, with the PEW-25 solution, that CR-39 is more suitable to distinguish α tracks from the proton background in our experiment. We also present a method to estimate the minimum detection range of α energy on specific etching conditions in our experiment.

Recyclable flame retardant phosphonated epoxy based thermosets enabled via a reactive approach

The development of reusable fire-safe polymers with a prolonged lifetime heralds the switch for a transition towards circular economy. In this framework, we report a novel phosphonated thermoset which is composed of networked phosphonate esters containing both PC and PO bonds. Employing a simple one-pot, two-step synthetic methodology, oxirane groups of the epoxy resin were partially reacted with various amounts of reactive bis H-phosphonate monomer, and cured with a cycloaliphatic hardener to obtain multifunctional thermosets with up to 8% phosphorus (P) content. Though 2.5% P was adequate to achieve good flame retardancy, a concentration > 5% P was necessary for accomplishing material reprocessability and recyclability. These phosphonated thermosets exhibited high Tg (94 °C – 140 °C) and good thermal stability. Fire performance of the thermoset with 2.5% P via cone calorimetry showed effective reduction in the peak heat release rate (pHRR, 75%) and significant inhibition of total smoke production (TSP, 72.5%), which was attributed to the gas and condense phase actions of the phosphonate moieties. This thermoset was explored as a transparent fire-safe coating on wood where an intumescent flame retardant mechanism was observed. The phosphonated thermoset with higher P content (6%) demonstrated excellent damage reparability and thermomechanical reprocessability driven by transesterification induced network rearrangement. This thermoset was used for manufacturing flax fiber reinforced composite, to demonstrate its future application as a polymer matrix for composite materials.

A method for background correction in 10Be detection: Evaluation of indirect isobaric interference by 7Be generated at the entrance window of a gas counter

This report presents a procedure for background correction of indirect isobaric interference by 10B in accelerator mass spectrometry of cosmogenic 10Be. A gas counter with an absorber cell for 10B is used as a detector. Injected ions are detected by two anode plates aligned in the main ionization chamber to plot the signals on a two-dimensional spectrum of loss and residual energies. Using this configuration, the tail of 10B events that manage to pass through the absorber cell can be separated from the 10Be events, but the total counts in the 10Be region are increased by 7Be generated from the reaction of 10B(1H,4He)7Be due to hydrogen attached on the surface of the entrance window of the absorber cell. Since the number of 7Be events are proportional to the counts of 4He events, we can evaluate the interference via statistical analyses for correlations between counting data for multiple regions of interest on the two-dimensional spectra. This correction results in an increase in uncertainty for the counting statistics, but improves the accuracy of the maximum likelihood value of the 10Be/9Be isotopic ratios.

Neutral Monodentate and Hypervalent Chalcogen Bond Catalysis on the Intramolecular Rauhut-Currier Reaction of Bis(enones): A DFT Study.

Recently, the green and high efficient of chalcogen bond (ChB) catalysis has been aroused great interest. In this work, the ChB catalysis has been applied to the intramolecular Rauhut-Currier (RC) reaction of bis(enones). The mechanism was divided into four processes: the promoter addition process, the carbon-carbon bond coupling process, the hydrogen transfer process, and the promoter elimination process. This study shows that the ChB catalyst could act on the promoter and reactant in the RC reaction, respectively. And the path 2 of ChB catalyst direct acting on the reactant is considered to be a relatively favorable channel of the reaction due to a lower energy barrier. In addition, all six catalysts could achieve good catalytic effect. Analysis of the properties shows that the formation of chalcogen bond mainly promotes the charge transfer of LP(O)-BD*(C-Se) in the carbon-carbon bond formation (key step), so that the charge of C(4) atom become more positive, thereby accelerating the reaction.

BPA‐Containing Polydopamine Nanoparticles for Boron Neutron Capture Therapy in a U87 Glioma Orthotopic Model

AbstractBoron neutron capture therapy (BNCT) is a promising therapy for refractory cancer based on the cytotoxic reaction of 10B (n, α) 7Li. Although two BNCT agents are clinically available, they are quickly metabolized and show modest enrichment in tumor sites, partially limiting BNCT widespread application. Consequently, novel agents that perform active targeting and show good biocompatibility have to be developed. Herein, boronophenylalanine‐containing polydopamine (B‐PDA) nanoparticles are easily fabricated by encapsulating boronophenylalanine (BPA) in polydopamine via nitrogen‐boronate coordination. In this study, B‐PDA achieves increased tumor accumulation and prolonged retention effects in the tumor site and superior antitumor activity post neutron irradiation in the orthotopic xenograft glioma model. In brief, this study offers a novel strategy for BPA delivery and may broaden the perspective on nanomedicine design for BNCT.

Study of Lithium Biodistribution and Nephrotoxicity in Skin Melanoma Mice Model: The First Step towards Implementing Lithium Neutron Capture Therapy.

Boron neutron capture therapy (BNCT) is one of the promising treatment methods for malignant melanoma. The main issue of this technology is the insufficient selectivity of 10B accumulation in tumor cells. As a result of the neutron absorption by boron, an 84% energy release occurred within the cell by the nuclear reaction 10B (n, α)7Li, which lead to tumor cell death. The use of lithium instead of boron brings a new unique opportunity-local 100% energy release-since all products of the 6Li (n, α)3H reaction have high linear energy transfer characteristics. The aim of this study was to determine the concentrations of Li in the tumor, skin, blood, brain and kidney in experimental animals with B16 melanoma and to analyze the potential Li toxicity after lithium carbonate administration at single doses of 300 and 400 mg/kg. Lithium carbonate was chosen since there is a long-term experience of its use in clinical practice for the treatment of psychiatric disorders. The inductively coupled plasma atomic emission spectrometry was used to evaluate Li concentrations in tissue samples. The accumulation efficiency of Li in the tumor was the highest at a time point of 30 min (22.4 µg/g; at a dose of 400 mg/kg). Despite the high lithium accumulation in the kidneys, the pathological changes in kidney tissues were not found. Thus, lithium may actually be used for the Li-NCT development and future studies can be conducted using 6Li and following irradiation of tumor cells using the schemes of lithium administration tested in this work.

Neutron spectroscopy with a high-pressure nitrogen-filled spherical proportional counter

The spherical proportional counter is a large volume gaseous detector which finds application in several fields, including direct Dark Matter searches. When the detector is filled with nitrogen it becomes an effective neutron spectrometer thanks to the 14N(n,α)11B and 14N(n,p)14C reactions. Nitrogen, however, is a challenging operating gas for proportional counters and requires a high electric field strength to gas pressure ratio. Benefiting from the latest advances in spherical proportional counter instrumentation and simulation techniques, we report first neutron measurements at operating pressures of up to 1.8bar. This achievement enhances the prospects of the spherical proportional counter to act as a neutron spectrometer appropriate for challenging environments, including underground laboratories, and industrial and medical settings.

Diverse Reactions of o-Carborane-Fused Silylenes with C≡E (E = C, P) Triple Bonds.

The reactivities of o-carborane-fused silylenes toward molecules with C≡E (E = C, P) bonds are reported. The reactions of bis(silylene) [(LSi:)C]2B10H10 (1a, L = PhC(NtBu)2) with arylalkynes afforded bis(silylium) carborane adducts 2 and 3, showing a Si(μ-C2)Si structure with an open-cage nido-carborane backbone. In contrast, the reaction of 1a with a phosphaalkyne AdC≡P (Ad = 1-adamantyl) smoothly furnished compound 4, comprising fused CPSi rings with a C=Si double bond and Si-Si single bond, and the related formation mechanism was investigated by DFT calculations. Furthermore, when monosilylene [(LSi:)C]CHB10H10 (1b) was employed to react with AdC≡P, compound 5 was isolated. The structure of 5 features a 1,2,3-triphosphetene core. All products were characterized by NMR spectroscopy and/or X-ray crystallography.

Measurement of the 235U(n,f) cross section relative to the 10B(n,α) reaction with Micromegas detectors at the CERN n_TOF facility: First results

Neutron cross section measurements are often made relative to a neutron cross section standard. Thus, the accuracy of the neutron standards determines the best possible accuracy of the neutron measurements. The 235U(n,f) cross section is widely used as reference, while it is considered a standard at thermal point and between 0.15 to 200 MeV. For this reason, additional cross section data for the 235U(n,f) reaction are useful in order to improve the accuracy and to extend the energy range of the standard. In this work, preliminary results of the measurement of the 235U(n,f) cross-section relative to the standard 10B(n,a) reaction are presented. The high accuracy measurement was performed at the experimental area EAR-1 of the n_TOF facility at CERN, aiming at covering the energy range from the thermal region up to approximately 100 keV. The samples were produced at JRC-Geel in Belgium, while the experimental setup was based on Micromegas detectors.

Proton boron fusion reaction: A novel experimental strategy for cross section investigation

The fusion reaction 11B(p,α)αα draws attention since the dawn of nuclear physics for its relevance and potential application in different fields, from nuclear fusion to astrophysics and hadron therapy. Nevertheless, the understanding and description of the physics of the reaction still have some important open points, both theoretical and experimental. Among others, the energy and angular distributions of α particles produced by the different reaction channels need to be further characterized, especially at low energies. To this aim, a novel experimental set-up was conceived by combining well-characterized boron-coated targets and a two-stage monolithic detection system. Targets were produced by Pulsed Laser Deposition, a technique that allows to finely tailor thickness, density and chemical composition of coatings. The detection system, based on a ΔE-E silicon telescope, was developed to perform an effective identification and discrimination between α particles produced by the p-11B reaction and primary protons, essential for the reaction kinematic analysis at low energies. Irradiations were performed by bombarding a boron-coated foil with primary protons of energies in the range 1–2.4 MeV. Results show the effectiveness of the particle discrimination. Measured energy distributions highlight the contribution of α particles generated in the two main reaction channels. A preliminary quantitative analysis of the reaction cross section was performed for each reaction channel at the different investigated energy and compared with literature data. The experimental set-up was also simulated through the Monte Carlo code FLUKA to test the model capabilities recently implemented in the code.

1,3,3,3′,3′-Pentaisopropyl-1,3,3′,6,6′,7,7′-heptahydro-1λ5-1,1′-spirobi[acenaphtho 5,6-cd][1,2,6]oxadiphosphinine]-3,3′-diium Triiodide

Reaction of bis(peri-substituted) triphosphine iPrP(AcenapPiPr2)2 (Acenap = acenaphthene-5,6-diyl) with iodine, followed by hydrolysis, afforded ionic species with [iPrP(AcenapP(O)iPr2)2] dication, containing P-O-P-O-P motif, balanced by triiodide anions. The new species were fully characterised, including single crystal X-ray diffraction. The formation of the unusual double-bridged motif is likely a result of crowding in the peri-region.

Systematic study of the fusion hindrance phenomenon using the proximity potential approach: signature of the energy-dependent effects of the surface energy coefficient

In the present study, we have systematically studied the role of surface energy coefficient as well as temperature dependence in the fusion hindrance phenomenon of the heavy-ion reactions using the proximity potential formalism. To this end, we have performed the calculations of the interaction potential using the original proximity potential 1977 (Prox. 77) and the fusion cross sections are calculated based on the coupled-channels (CC) approach. The considered fusion systems are including the heavy-ion reactions 11B+197Au, 12C+198Pt, 16O+208Pb, 28Si + 64Ni, 28Si + 94Mo, 58Ni+58Ni, 32S+89Y,34S+89Y, 12C+204Pb and 36S + 64Ni with conditions of Q <0 and charge product of the participant nuclei 392≤ Z1Z2 ≤784. Our preliminary calculations show the Prox. 77 model predicts the theoretical values ​​of the fusion cross-sections less than the corresponding experimental data especially in the energy regions below the fusion barrier. However, the imposing of the mentioned physical effects increases the calculated values of the fusion cross sections and thus improves their agreement with the experimental cross sections for the selected reactions. In addition, by considering the energy dependence on the surface energy constant γ0 of the proximity formalism at the low energy region we are able to reproduce well the fusion cross sections, the astrophysical factor S(E) as well as the logarithmic derivative L(E) in these regions.‎

Neutron spectroscopy with N2-filled high-pressure large-volume spherical proportional counters

Precise in-situ measurements of the neutron flux in underground laboratories is crucial for direct dark matter searches, as neutron induced backgrounds can mimic the typical dark matter signal. The development of a novel neutron spectroscopy technique using Spherical Proportional Counters is investigated. The detector is operated with nitrogen and is sensitive to both fast and thermal neutrons through the 14N(n, α)11B and 14N(n, p)14C reactions. This method holds potential to be a safe, inexpensive, effective, and reliable alternative to 3He-based detectors. Measurements of fast and thermal neutrons from an Am-Be source with a Spherical Proportional Counter operated at pressures up to 2 bar at Birmingham are discussed.