Coupling Route Research Articles

Impact of hole scavengers on photocatalytic reduction of nitrobenzene using cadmium sulfide quantum dots

One key factor that affects the reaction yield and selectivity of nanoparticle-catalyzed photochemical reactions is the type of hole scavengers. In this work, we examine the effect of hole scavengers in photoreduction of nitrobenzene catalyzed by cadmium sulfide quantum dots. We discover that the hole scavengers can determine the reduction pathway as well as the final product. Specifically, when methanol is the solvent and the sole hole scavenger, or when it is used in conjunction with ascorbic acid, ammonium formate, mercaptopropionic acid, or sodium borohydride, the reaction follows a direct reduction pathway. In contrast, with methanol and sodium sulfite, the reaction proceeds via a coupling route. Some hole scavengers directly participate in the redox reaction of intermediates. This study demonstrates that the type of hole scavenger can alter the reaction pathways and determine the reaction outcome and should be chosen with careful consideration. • Nitrobenzene is photo-catalytically reduced by CdS quantum dots with hole scavengers • Different hole scavenger combinations lead to different products • The type of hole scavenger affects reaction times and pathways The role of hole scavengers in photocatalysis is often regarded to be removing the holes in photocatalysts by donating electrons to them. Mureithi et al. show that the effect of hole scavengers goes beyond removal of holes to affecting the reaction time, pathways, and products in photocatalytic reactions.

Theoretical Studies on the Photophysical Properties of the Ag(I) Complex for Thermally Activated Delayed Fluorescence Based on TD-DFT and Path Integral Dynamic Approaches.

Theoretical calculation not only is a powerful tool to deeply explore photophysical processes of the emitters but also provides a theoretical basis for material renewal and design strategy in the future. In this work, the interconversion and decay rates of the thermally activated delayed fluorescence (TADF) process of the rigid Ag(dbp)(P2-nCB) complex are quantitatively calculated by employing the optimally tuned range-separated hybrid functional (ω*B97X-D3) method combined with the path integral approach to dynamics considering the Herzberg–Teller and the Duschinsky rotation effects within a multimode harmonic oscillator model. The calculated results show that the small energy splitting ΔE(S1–T1) = 742 cm–1 (experimental value of 650 cm–1) of the lowest singlet S1 and triplet T1 state and proper vibrational spin–orbit coupling interactions facilitate the reverse intersystem crossing (RISC) processes from the T1 to S1 states. The kRISC rate is estimated to be 1.72 × 108 s–1 that is far more than the intersystem crossing rate kISC of 7.28 × 107 s–1, which will greatly accelerate the RISC process. In addition, the multiple coupling routes of zero-field splitting (ZFS) interaction can provide energetically nearby lying states, to speed up the RISC pathway, and restrict the phosphorescence decay rate. A smaller ZFS D-tensor of 0.143 cm–1, E/D ≈ 0.094 ≪ 1/3, and Δg > 0 are obtained, indicating that the excited singlet states are hardly mixed into the T1 state; thus, a lower phosphorescence decay rate (kp = 9.29 × 101 s–1) is expected to occur, and the T1 state has a long lifetime, which is helpful for the occurrence of the RISC process. These works are in excellent agreement with the experimental observation and are useful for improving and designing efficient TADF materials.

Ion Channel Partnerships: Odd and Not-So-Odd Couples Controlling Neuronal Ion Channel Function.

The concerted function of the large number of ion channels expressed in excitable cells, including brain neurons, shapes diverse signaling events by controlling the electrical properties of membranes. It has long been recognized that specific groups of ion channels are functionally coupled in mediating ionic fluxes that impact membrane potential, and that these changes in membrane potential impact ion channel gating. Recent studies have identified distinct sets of ion channels that can also physically and functionally associate to regulate the function of either ion channel partner beyond that afforded by changes in membrane potential alone. Here, we review canonical examples of such ion channel partnerships, in which a Ca2+ channel is partnered with a Ca2+-activated K+ channel to provide a dedicated route for efficient coupling of Ca2+ influx to K+ channel activation. We also highlight examples of non-canonical ion channel partnerships between Ca2+ channels and voltage-gated K+ channels that are not intrinsically Ca2+ sensitive, but whose partnership nonetheless yields enhanced regulation of one or the other ion channel partner. We also discuss how these ion channel partnerships can be shaped by the subcellular compartments in which they are found and provide perspectives on how recent advances in techniques to identify proteins in close proximity to one another in native cells may lead to an expanded knowledge of other ion channel partnerships.

A perspective on nonlinearities in coherent magnetization dynamics

The recent thrust in ultrafast magnetization dynamics aims at extending spintronic functionalities to terahertz frequencies. Deterministic manipulation of magnetization at the corresponding ultrashort timescales requires minute control not only over the magnetization itself but also the reservoirs it is interacting with. Although the various intricate couplings between spins, phonons, and electrons—all of which are susceptible to ultrashort laser pulses—lead to many (often nonlinear) coupling routes, magnetization-dynamical nonlinearities have remained largely underexplored. In this Perspective, we highlight recent advances and foresee future developments in the rapidly evolving field of nonlinear magnetization dynamics. Given the elementary character of coherent excitations, we put particular emphasis on their nonlinearities. We briefly review theoretical aspects and assess excitation mechanisms to reach the nonlinear regime of magnetic excitations in a broad class of magnetic materials, such as ferromagnets, antiferromagnets, and ferrimagnets. We present an overview of the groundbreaking experiments that showcase the unique insights provided by magnetic nonlinearities. We conclude by discussing open challenges and opportunities that underpin the potential of nonlinear magnetization dynamics for the advancement of spintronics and cavity quantum electrodynamics with spin waves at terahertz frequencies.

Directed ortho and Remote Metalation-Suzuki-Miyaura Cross Coupling Route to Azafluorenol Core Liquid Crystals.

Two new smectic C* mesogens containing a hexyloxy side chain and an azafluorenone (3a) or azafluorenol (3b) core were synthesized using a combined directed ortho metalation-directed remote metalation-Suzuki-Miyaura cross-coupling strategy. 3b was formed in 10 steps and 25% overall yield based on starting benzamide 1a. 3a forms a nematic phase, while 3b forms a smectic A phase. The large temperature range of the smectic phase for the azafluorenol 3b is indicative of mesophase stabilization by intermolecular hydrogen bonding between the hydroxyl group and pyridine nitrogen of neighboring 3b molecules.

Amino-Heterocycle Tetrahydroisoquinoline CXCR4 Antagonists with Improved ADME Profiles via Late-Stage Buchwald Couplings.

This work surveys a variety of diamino-heterocycles as an isosteric replacement for the piperazine substructure of our previously disclosed piperarinyl-tetrahydroisoquinoline containing CXCR4 antagonists. A late-stage Buchwald coupling route was developed for rapid access to final compounds from commercial building blocks. Among 13 analogs in this study, compound 31 embodying an aza-piperazine linkage was found to have the best overall profile with potent CXCR4 inhibitory activity and favorable in vitro absorption, distribution, metabolism, and excretion (ADME) properties. An analysis of the calculated physiochemical parameters (ROF, cLogD) and the experimental ADME attributes of the analogs lead to the selection of 31 for pharmacokinetic studies in mice. Compared with the clinical compound AMD11070, compound 31 has no CYP450 3A4 or 2D6 inhibition, higher metabolic stability and PAMPA permeability, greatly improved physiochemical parameters, and superior oral bioavailability (%F = 24). A binding rationale for 31 within CXCR4 was elucidated from docking and molecular simulation studies.

Catalytic nonthermal plasma using efficient cobalt oxide catalyst for complete mineralization of toluene

The remarkable rise in industrial utilization of volatile organic compounds has increased their presence in environmental matrices, which is a menace for human health. Conventionally, many technologies are in practice for constricting their escape to the environment. However, due to associated adverse health hazards, more efficient technique ensuring complete mineralization is inevitably demanded. In the current study, the degradation of toluene by post-plasma catalysis using cobalt-coupled (Co3O4–CoO) catalyst was studied. Firstly, a new starch-assisted synthesis route for cobalt coupling is presented. Secondly, the research finding of this study showed that the formed cobalt couple exhibited robust performance for toluene degradation up to 99%, which was attributed to their enhanced redox property and adsorbed oxygen content. This promotion in catalytic ability is due to intrinsically greater oxygen storage capacity of coupling. Additionally, the results of this study indicated that toluene degradation was increased significantly with higher input power, whereas, without catalyst application, nonthermal plasma (NTP) alone produced other VOCs as a result of toluene degradation and higher NO concentration at high input power and higher O3 at low input power. Furthermore, it could be concluded that NTP along with cobalt-coupled catalyst promotes toluene degradation, controls the production of all other VOCs and O3 and significantly reduced the production of NO concentration.

WHOLE CORE COUPLING METHODOLOGIES WITHIN WIMS

The ANSWERS® WIMS reactor physics code is being developed for whole core multiphysics modelling. The established neutronics capability for lattice calculations has recently been extended to be suitable for whole core modelling of Small Modular Reactors (SMRs). A whole core transport, SP3 or diffusion flux solution is combined with fuel assembly resonance shielding and pin-by-pin differential depletion. An integrated thermal hydraulic solver permits differential temperature and density variations to feedback to the neutronics calculation. This paper presents new methodology developed in WIMS to couple the core neutronics to the integrated core thermal hydraulics solver. Two coupling routes are presented and compared using a challenging PWR SMR benchmark. The first route, called GEOM, dynamically calculates the resonance shielding and homogenisation with the whole core flux solution. The second coupling route, called CAMELOT, separates the resonance shielding and pincell homogenisation from the whole core solution via generating tabulated cross sections. Both routes can use the MERLIN homogenised pin-by-pin whole core flux solver and couple to the same integrated thermal hydraulic solver, called ARTHUR. Heterogeneous differences between the neutronics and thermal hydraulics are mapped via thermal identifiers for neutronics materials and thermal regions. The ability for the integrated thermal hydraulic solver to call an external code via a Fortran-C-Python (FCP) interface is also summarised. This flexible external coupling permits one way coupling to an external fuel performance code or two way coupling to an external thermal hydraulic code.

Oxidative Dehydrogenation of Methane When Using TiO2- or WO3-Doped Sm2O3 in the Presence of Active Oxygen Excited with UV-LED

There are active oxygen species that contribute to oxidative coupling or the partial oxidation during the oxidative dehydrogenation of methane when using solid oxide catalysts, and those species have not been definitively identified. In the present study, we clarify which of the active oxygen species affect the oxidative dehydrogenation of methane by employing photo-catalysts such as TiO2 or WO3, which generate active oxygen from UV-LED irradiation conditions under an oxygen flow. These photo-catalysts were studied in combination with Sm2O3, which is a methane oxidation coupling catalyst. For this purpose, we constructed a reaction system that could directly irradiate UV-LED to a solid catalyst via a normal fixed-bed continuous-flow reactor operated at atmospheric pressure. Binary catalysts prepared from TiO2 or WO3 were either supported on or kneaded with Sm2O3 in the present study. UV-LED irradiation clearly improved the partial oxidation from methane to CO and/or slightly improved the oxidative coupling route from methane to ethylene when binary catalysts consisting of Sm2O3 and TiO2 are used, while negligible UV-LED effects were detected when using Sm2O3 and WO3. These results indicate that with UV-LED irradiation the active oxygen of O2− from TiO2 certainly contributes to the activation of methane during the oxidative dehydrogenation of methane when using Sm2O3, while the active oxygen of H2O2 from WO3 under the same conditions afforded only negligible effects on the activation of methane.

A thermolytic route to a polysilyne.

We report a safe and convenient method to prepare a new class of network polysilane, or polysilyne ([RSi]n). Simple thermolysis of a readily accessible linear poly(phenylsilane), [PhSiH]n, affords polysilyne [PhSi]n with concomitant evolution of monosilanes. This new polymer shows a hyperbranched structure with unique features not observed in known polysilynes prepared via hazardous Wurtz coupling routes. Despite these differences, our soluble, yellow polysilyne exhibits some important properties associated with the traditional random network structure: it absorbs up to 400 nm in the UV spectrum, yet is stable to photolysis under inert atmosphere. This efficient new synthetic route opens the door to exciting applications for these hyperbranched polymers in materials and device technologies.

One-pot access to 2-amino-3-arylbenzofurans: direct entry to polyheterocyclic chemical space.

As a means to make new benzofuran-embedded polycyclic structures, we established two efficient one-pot sequential coupling routes to 2-amino-3-arylbenzofurans and 2-amino-3-arylnaphtho[2,1-b]furans. Further ring formation (six- and seven-membered rings) with the resulting amine moiety at the C2 position of benzofurans was realized, leading to further expansion of benzofuran-based chemical space.

Unusually Fast Phosphorescence from Ir(III) Complexes via Dinuclear Molecular Design.

The design and detailed photophysical study of two novel Ir(III) complexes featuring mono- and dinuclear design are presented. Emission quantum yield and decay times in solution are ΦPL = 90% and τ(300 K) = 1.16 μs for the mononuclear complex 5, and ΦPL = 95% and τ(300 K) = 0.44 μs for the dinuclear complex 6. These data indicate an almost 3-fold increase in the phosphorescence rate for dinuclear complex 6 compared to 5. Zero-field splitting (ZFS) of the T1 state also increases from ZFS = 65 cm-1 for the mononuclear complex to ZFS = 205 cm-1 for the dinuclear complex and is accompanied by a drastic shortening of the individual decay times of T1 substates. With the help of TD-DFT calculations, we rationalize that the drastic changes in the T1 state properties in the dinuclear complex originate from an increased number of excited states available for direct spin-orbit coupling (SOC) routes as a result of electronic coupling of Ir-Cl antibonding molecular orbitals of the two coordination sites.

The effect of aperture shape, angle of incidence and polarization on shielding effectiveness of metallic enclosures

Apertures and slots of the enclosures come into prominence for heat allocation, ventilation, I/O cable, etc. These slots and apertures induce the coupling route of electromagnetic interference (EMI) from the inside to outside. So, electromagnetic shielding is usually used to decrease the emissions or to the progress of equipment immunity. In this paper, an effect of an aperture shape on the performance of electrical shielding effectiveness has been investigated by means of simulation. Rectangular, square, circular, equilateral triangle and hexagonal shape apertures that have a constant area of 5625 mm2 have been studied in addition to polarization type of applied electromagnetic field. It has been observed that ESE depends on the electric field direction and plane wave polarization and rectangular shape aperture has more effective ESE performance than square, circular, equilateral triangle and hexagonal type apertures. Rectangular shaped aperture has approximately 43 dB better performance than equilateral triangle one for whole frequency band of 100 MHz to 1GHz. Rectangular, square, circular, hexagonal and equilateral triangle type apertures have been ranked from best performance to the worst with respect to their ESE. There have been considerable findings that can be useful for enclosure designers about the effect of angle of incidence and polarization angle.

Insight into the effect of surface structure for Pd catalyst on CO oxidative coupling to dimethyl oxalate

CO oxidative coupling to dimethyl oxalate (DMO) on Pd(100), (110) and (211) surfaces have been investigated through the density functional theory (DFT) method together with periodic slab models. Effect of different surface structures on adsorption, reaction and catalytic activity has been explored. CO at different adsorption sites participated in the oxidative coupling reaction according to the surface structure. CO at bridge or hollow site was consumed for the coupling reaction on the Pd(100) surface, and the favorable route was COOCH3-COOCH3 coupling path. While CO-COOCH3 coupling route was the optimal on Pd(110) and (211) surfaces, CO at top and bridge site took part in the reaction, respectively. Pd(100) surface exhibited higher catalytic activity and selectivity to DMO than Pd(110) and (211) surfaces.

Broadband linearly/circularly polarized microstrip filtering antennas

AbstractTwo linearly and circularly polarized filtering antennas with low profile, broad bandwidth, and improved gain are proposed. Without increasing the antenna profile, a vertically coupled resonant structure, which can broaden the bandwidth and provide the filtering response, is employed. To prove the concept, a broadband linearly polarized (LP) filtering antenna is designed by integrating the hairpin resonator on the feed, U‐slot resonator in the ground and the patch resonator. Then, we design a broadband circularly polarized (CP) filtering antenna, which utilizes a single‐feed dual‐coupled structure for two coupling routes with 90° phase difference to excite two orthogonal resonant modes without power divider and phase delay line. Both antennas exhibit third‐order filtering characteristics with improved bandwidths and flat in‐band gain. The equivalent circuits of both antennas are discussed. The LP and CP antennas achieve an impedance band of 28% and 29.6%, respectively. The CP antenna shows a 3‐dB axial ratio bandwidth of 17.6%. Both antennas also exhibit the high gain of 9.5 dBic with less than 0.6 dB variation within the band.

Design of a Microstrip Diplexer-Integrated Filtering Power Divider

This study proposed a new method and structure for designing a diplexer-integrated filtering power divider. A filtering function with equal power division was integrated with a diplexer. The multifunctional diplexer comprised eight coupled resonators and two 50-Ω resistors with a distributed coupling structure. Moreover, a connected coupling technique provided improved flexibility and freedom to construct the diplexer. High isolation was obtained using the proposed coupling configuration through the introduction of out-of-phase cancellation between multiple coupling routes. Moreover, because the distributed coupling structure was employed as an input, no complex matching network was required; this significantly reduced the size and simplified the design of the diplexer. Moreover, each channel passband was individually designed. For demonstration, a multifunctional diplexer operating at 1 and 1.15 GHz with a second-order Chebyshev bandpass response and equal power splitting was designed and fabricated using microstrip technology, and the simulation results were consistent with the measured results.

Computational Exploration of Mechanistic Avenues in C-H Activation Assisted Pd-Catalyzed Carbonylative Coupling.

The detailed mechanism of the intermolecular Pd-catalyzed carbonylative coupling reaction between aryl bromides and polyfluoroarenes relying on C(sp2)-H activation was investigated using state-of-the-art computational methods (SMD-B3LYP-D3(BJ)/BS2//B3LYP-D3/BS1). The mechanism unveils the necessary and important roles of a slight excess of carbon monoxide: acting as a ligand in the active catalyst state, participating as a reactant in the carbonylation process, and accelerating the final reductive elimination event. Importantly, the desired carbonylative coupling route follows the rate-limiting C-H activation process via the concerted metalation-deprotonation pathway, which is slightly more feasible than the decarboxylative route leading to byproduct formation by 1.2 kcal/mol. The analyses of the free energies indicate that the choice of base has a significant effect on the reaction mechanism and its energetics. The Cs2CO3 base guides the reaction toward the coupling route, whereas carbonate bases such as K2CO3 and Na2CO3 switch toward an undesired decarboxylative path. However, K3PO4 significantly reduces the C-H activation barrier over the decarboxylation reaction barrier and can act as a potential alternative base. The positional influence of a methoxy substituent in bromoanisole and different substituent effects in polyfluoroarenes were also considered. Our results show that different substituents impose significant impact on the desired carbonylative product formation energetics. Considering the influence of several ligands leads to the conclusion that other phosphine and N-heterocyclic carbene, such as P nBuAd2 and IMes, can be used as an efficient alternative than the experimentally reported P tBu3 ligand exhibiting a clear preference for C-H activation (ΔΔ⧧ GLS) by 7.1 and 10.9 kcal/mol, respectively. We have also utilized the energetic span model to interpret the experimental results. Moreover, to elucidate the origin of activation barriers, energy decomposition analysis calculations were accomplished for the critical transition states populating the energy profiles.

Unravelling overlaps and torsion-facilitated coupling using two-dimensional laser-induced fluorescence

Two-dimensional laser-induced fluorescence (2D-LIF) spectroscopy is employed to identify contributions to fluorescence excitation spectra that arise from both overlapping bands and coupling between zero-order states (ZOSs). Evidence is found for the role of torsional motion in facilitating the coupling between vibrations that particularly involves the lowest-wavenumber out-of-plane vibrational modes. The experiments are carried out on jet-cooled p-fluorotoluene, where the molecules are initially in the lowest two torsional levels. Here we concentrate on the 390–420 cm−1 features in the S1 ← S0 excitation spectrum, assigning the features seen in the 2D-LIF spectrum, aided by separate dispersed fluorescence spectra. The 2D-LIF spectra allow the overlapping contributions to be cleanly separated, including some that arise from vibrational-torsional coupling. Various coupling routes open up because of the different symmetries of the lowest two torsional modes; these combine with the vibrational symmetry to provide new symmetry-allowed vibration-torsion (‘vibtor’) interactions, and the role of the excited m = 1 torsional level is found to be significant.

Radical Fragment Coupling Route to Geminal Bis(boronates).

The radical addition of dithiocarbonates to 1,1-bis(boronyl)-3-butene and related alkenes occurs without complications from fragmentation or hydrogen atom abstraction and delivers a vast array of highly functional geminal bis(boronates). The ability to assemble geminal bis(boronates) bearing polar functional groups not readily obtained through existing methods is particularly noteworthy. This approach also opens up access to geminal bis(boronyl) cyclopropanes and geminal bis(boronyl) tetrahydroquinolines.

Synthesis of Pyrazines and Quinoxalines via Acceptorless Dehydrogenative Coupling Routes Catalyzed by Manganese Pincer Complexes.

Base-metal catalyzed dehydrogenative self-coupling of 2-amino alcohols to selectively form functionalized 2,5-substituted pyrazine derivatives is presented. Also, 2-substituted quinoxaline derivatives are synthesized by dehydrogenative coupling of 1,2-diaminobenzene and 1,2-diols. In both cases, water and hydrogen gas are formed as the sole byproducts. The reactions are catalyzed by acridine-based pincer complexes of earth-abundant manganese.