Search

Focuses on a study which compared computations of Navier Stokes and reduced Navier Stokes solvers in a stenosis. Materials and methods; Results; Discussion and conclusion.

EMD-95885, 6-[3-[4-(4-fluorobenzyl)piperidino]propionyl]-3H-benzoxazol-2-one (1) has been described as a selective antagonist for the NMDA receptors containing NR2B subunits, displaying an IC50 of 3.9 nM for this subtype. EMD-95885 (1) has been synthesized in good overall yield and labelled with carbon-11 (T1/2: 20.4 min) at its benzoxazolinone moiety using [11C]phosgene. The pharmacological profile of [11C]EMD-95885 ([11C]-1) was evaluated in vivo in rats with biodistribution studies and brain radioactivity monitored with intracerebral radiosensitive β-microprobes. The brain uptake of [11C]-1 was homogeneous (0.4–0.6% ID/mL) across the different brain structures studied. This in vivo brain regional distribution of [11C]-1 was not consistent with the known distribution of NR2B subunits. Also as a measure of specificity the hippocampus/cerebellum ratio reached 0.8 throughout the time course of the experiment supporting the lack of specificity. Competition studies with the NR2B prototypic ligand ifenprodil and EMD-95885 (1), 30 min before the radioligand injection, displayed homogeneous reduction of [11C]-1 uptake of 40–60%. Pre-treatment of rats with DTG (σ ligand), MDL105519 (glycine site antagonist) and MK801 (ion channel blocker) had no inhibitory effect on [11C]-1 uptake. Use of haloperidol as a blocking drug also resulted in a homogeneous inhibition of [11C]-1 uptake by 66–60%, which does not reflect binding to dopamine or σ receptors. Due to the homogeneous radioligand uptake and inhibition and no measure of cerebral blood flow effects during these blocking studies it is uncertain whether any specific binding is observed. In view of these results, [11C]EMD-95885 ([11C]-1) does not have the required properties for imaging NR2B containing NMDA receptors using positron emission tomography. [Copyright &y& Elsevier]

Diradicals based on a meta-quinodimethane (m-QDM) scaffold generally have a triplet ground state and are rather scarce. Herein, m-QDM-based non-Kekulé diradicals [3,3'-(NHC) 2 BP] (3-NHC) (NHC = SIPr = C{N(Dipp)CH 2 } 2 ; IPr = C{N(Dipp)CH} 2 , Me-IPr = C{N(Dipp)CMe} 2 ; Dipp = 2,6-iPr 2 C 6 H 3 ; BP = 1,1'-C 6 H 4 C 6 H 4 ) featuring N-heterocyclic carbene (NHC) pendants are reported as crystalline solids. The EPR spectra of 3-NHC show both allowed (Δm s = 1) and forbidden (Δm s = 2; 'half-field') transitions characteristic for triplet diradicals. Variable temperature EPR studies however reveal a singlet ground state for 3-SIPr. Consistent with the EPR spectra, calculations predict a remarkably small singlet-triplet energy gap (ΔE ST ≤ 0.26 kcal/mol) for the 3-NHC compounds. The calculated singlet diradical character for the ground states of the 3-NHC compounds amounts to ~99 %., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

We present the design and comprehensive investigation of stable para-substituted triarylamine-2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) radical ion pairs (RIPs) generated via single-electron transfer (SET). We quantified the degree of SET in both solution and solid phases, utilising a suite of spectroscopic techniques including IR, EPR, NMR, and single-crystal X-ray diffraction (SC-XRD). Our findings reveal that the extent of SET is significantly influenced by the nature of the substituents (MeO > t Bu > Br) and the polarity of the solvent (MeCN > DCM > toluene). The radical ion pair [(pMeOPh) 3 N]⋅ + [DDQ]⋅ - was unambiguously identified using EPR and UV-vis spectroscopy, and its structure was confirmed by SC-XRD. Detailed analysis indicates an open-shell singlet ground state with a thermally accessible triplet state, as corroborated by EPR, magnetic susceptibility measurements, and DFT calculations. This study offers crucial insights into the mechanistic pathways of RIP formation and tuning both in solution and solid states, laying the groundwork for future exploration of their reactivity and potential applications., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Colloidal quantum dots (QDs) with a wide color gamut and high luminescent efficiency are promising for next-generation electronic and photonic devices. However, precise and scalable patterning of QDs without degrading their properties and their integration into commercially relevant devices, such as digitally addressable QD light-emitting diode (QLED) displays, remain challenging. Here, we develop electronically optimized diazirine-based cross-linkers for nondestructive, direct photopatterning of QDs and, ultimately, building the active-matrix QLED displays. The key to the cross-linker design is the introduction of electron-donating substituents that permit the formation of ground-state singlet carbenes for air-stable and benign QD photopatterning. Under ambient conditions, these cross-linkers enable the patterning of heavy metal-free QDs at a resolution of over 13,000 pixels per inch using commercial i-line photolithography. The patterned QD layers fully preserved their optical and optoelectronic properties. Pixelated electroluminescent devices with patterned InP/ZnSe/ZnS QD layers show a peak external quantum efficiency of 15.3% and a maximum luminance of about 40,000 cd m -2 , outperforming those made by existing QD patterning approaches. We further show the seamless integration of patterned QLEDs with thin-film transistor circuits and the fabrication of dual-color active-matrix displays. These results underscore the importance of designing photochemistry for QD patterning, and promise the implementation of direct photopatterning methods in manufacturing commercial QLED displays and other integrated QD device platforms.

The local coordination environment of single atom catalysts (SACs) often determines their catalytic performance. To understand these metal-support interactions, we prepared Pt SACs on cerium dioxide (CeO 2 ) cubes, octahedra and rods, with well-structured exposed crystal facets. The CeO 2 crystals were characterized by SEM, TEM, pXRD, and N 2 sorption, confirming the shape-selective synthesis, identical bulk structure, and variations in specific surface area, respectively. EPR, XPS, TEM and XANES measurements showed differences in the oxygen vacancy density following the trend rods > octahedra > cubes. AC-HAADF-STEM, XPS and CO-DRIFTS measurements confirmed the presence of only single Pt 2+ sites, with different surface platinum surface concentrations. We then compared the performance of the three catalysts in ammonia borane hydrolysis. Precise monitoring of reaction kinetics between 30-80 °C gave Arrhenius plots with hundreds of data points. All plots showed a clear inflection point, the temperature of which (rods > octahedra > cubes) correlates to the energy barrier of ammonia borane diffusion to the Pt sites. These activity differences reflect variations in the - facet dependent - degree of stabilization of intermediates by surface oxygen lone pairs and surface-metal binding strength. Our results show how choosing the right macroscopic support shape can give control over single atom catalysed reactions on the microscopic scale., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Radical-type carbene transfer catalysis is an efficient method for the direct functionalization of C-H and C=C bonds. However, carbene radical complexes are currently formed via high-energy carbene precursors, such as diazo compounds or iodonium ylides. Many of these carbene precursors require additional synthetic steps, have an explosive nature, or generate halogenated waste. Consequently, the utilization of carbene radical catalysis is limited by specific carbene precursors that access the carbene radical intermediate. In this study, we generate a cobalt(III) carbene radical complex from dimethyl malonate, which is commercially available and bench-stable. EPR and NMR spectroscopy were used to identify the intermediates and showed that the cobalt(III) carbene radical complex is formed upon light irradiation. In the presence of styrene, carbene transfer occurred, forming cyclopropane as the product. With this photochemical method, we demonstrate that dimethyl malonate can be used as an alternative carbene precursor in the formation of a cobalt(III) carbene radical complex., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

In recent years, there has been a growing demand for drug design approaches that incorporate a higher number of sp 3 -hybridized carbons, necessitating the development of innovative cross-coupling strategies to reliably introduce aliphatic fragments. Here, we present a powerful approach for the light-mediated B-alkyl Suzuki-Miyaura cross-coupling between alkyl boranes and aryl bromides. Alkyl boranes were easily generated via hydroboration from readily available alkenes, exhibiting excellent regioselectivity and enabling the selective transfer of a diverse range of primary alkyl fragments onto the arene ring under photocatalytic conditions. This methodology eliminates the need for expensive catalytic systems and sensitive organometallic compounds, operating efficiently at room temperature within just 30 min. We further demonstrate the translation of the present protocol to continuous-flow conditions, enhancing scalability, safety, and overall efficiency of the method. This versatile approach offers significant potential for accelerating drug discovery efforts by enabling the introduction of complex aliphatic fragments in a straightforward and reliable manner., (© 2024. The Author(s).)

N-Heterocyclic carbene (NHC) analogues of Wittig hydrocarbon, [(NHC)(Stil)(NHC)] (3a-c) (NHC = SIPr (1a) = C[N(Dipp)CH 2 ] 2 , Dipp = 2,6-iPr 2 C 6 H 3 ; IPr (1b) = C[N(Dipp)CH] 2 ; Me-IPr (1c) = C[N(Dipp)CMe] 2 and Stil = C 6 H 4 CHCHC 6 H 4 ) have been reported as crystalline solids. 3a-c are prepared by two-electron reductions of the corresponding bis-1,3-imidazoli(ni)um bromides [(NHC)(Stil)NHC)](Br) 2 (2a-c) with KC 8 in >94 % yields. 2a-c are accessible by the nickel catalyzed direct C-C coupling of NHCs (1a-c) with (E)-4,4'-dibromostilbene. One-electron oxidation of 3a,b yields the corresponding radical cations [(NHC)(Stil)NHC)]B(C 6 F 5 ) 4 4a,b. All compounds have been characterized by UV-Vis/NMR/EPR spectroscopy as well as 2a, 3a, and 3b by single crystal X-ray diffraction. The electronic structures of representative systems have been analyzed by quantum chemical calculations., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The field of bioorthogonal chemistry is rapidly growing, presenting successful applications of organic and transition metal-catalysed reactions in cells and living systems (in vivo). The development of such reactions typically proceeds through many iterative steps focused on biocompatibility and fast reaction kinetics to ensure product formation. However, obtaining kinetic data, even under simulated biological (biomimetic) conditions, remains a challenge due to substantial concentrations of salts and biomolecules hampering the use of typically employed solution-phase analytical techniques. In this study, we explored the suitability of gas evolution as a probe to study kinetics under biomimetic conditions. As proof of concept, we show that the progress of two transition metal-catalysed bioorthogonal chemical reactions can be accurately monitored, regardless of the complexity of the medium. As such, we introduce a protocol to gain more insight into the performance of a catalytic system under biomimetic conditions to further progress iterative catalyst development for in vivo applications., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Performing transition metal-catalyzed reactions in cells and living systems has equipped scientists with a toolbox to study biological processes and release drugs on demand. Thus far, an impressive scope of reactions has been performed in these settings, but many are yet to be introduced. Nitrene transfer presents a rather unexplored new-to-nature reaction. The reaction products are frequently encountered motifs in pharmaceuticals, presenting opportunities for the controlled, intracellular synthesis of drugs. Hence, we explored the transition metal-catalyzed sulfimidation reaction in water for future in vivo application. Two Cu(I) complexes containing trispyrazolylborate ligands (Tp x ) were selected, and the catalytic system was evaluated with the aid of three fitness factors. The excellent nitrene transfer reactivity and high chemoselectivity of the catalysts, coupled with good biomolecule compatibility, successfully enabled the sulfimidation of thioethers in aqueous media. We envision that this copper-catalyzed sulfimidation reaction could be an interesting starting point to unlock the potential of nitrene transfer catalysis in vivo., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Polyurethane coatings have strong material properties due to the hydrogen bonding inherent to the urethane groups. However, installing this urethane moiety usually requires curing through difficult-to-handle isocyanates. In this work, we show the development of a polyurethane-based crosslinker that can be used to formulate a one-component polyurethane coating with material properties similar to those of isocyanate-based polyurethane coatings. To achieve this, we used diazirine functionalities that generate carbenes upon heating, which react with alcohol functionalities in a polyol to generate a crosslinked network with a high storage modulus., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Asymmetric hydrogenation finds widespread application in academia and industry. And indeed, a number of processes have been implemented for the production of pharma and agro intermediates as well as flavors & fragrances. Although these processes are all based on the use of late transition metals as catalysts, there is an increasing interest in the use of base metal catalysis in view of their lower cost and the expected different substrate scope. Catalysts based on cobalt have already shown their potential in enantioselective hydrogenation chemistry. This review outlines the impressive progress made in recent years on cobalt-catalyzed asymmetric hydrogenation of different unsaturated substrates. We also illustrate the ligand dependent substrate specificity as well as the mechanistic variability in detail. This may well guide further catalyst development in this research area., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Oxidation of an iridium(III) oxo precursor enabled the structural, spectroscopic, and quantum-chemical characterization of the first well-defined iridium(IV) oxo complex. Side-by-side examination of the proton-coupled electron transfer thermochemistry revealed similar driving forces for the isostructural oxo complexes in two redox states due to compensating contributions from H + and e - transfer. However, C-H activation of dihydroanthracene revealed significant hydrogen tunneling for the distinctly more basic iridium(III) oxo complex. Our findings complement the growing body of data that relate tunneling to ground state properties as predictors for the selectivity of C-H bond activation., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Here, we present the development and characterization of the novel PhenTAA macrocycle as well as a series of [Ni(R 2 PhenTAA)] n complexes featuring two sites for ligand-centered redox-activity. These differ in the substituent R (R = H, Me, or Ph) and overall charge of the complex n (n = -2, -1, 0, +1, or +2). Electrochemical and spectroscopic techniques (CV, UV/vis-SEC, X-band EPR) reveal that all redox events of the [Ni(R 2 PhenTAA)] complexes are ligand-based, with accessible ligand charges of -2, -1, 0, +1, and +2. The o -phenylenediamide (OPD) group functions as the electron donor, while the imine moieties act as electron acceptors. The flanking o -aminobenzaldimine groups delocalize spin density in both the oxidized and reduced ligand states. The reduced complexes have different stabilities depending on the substituent R. For R = H, dimerization occurs upon reduction, whereas for R = Me/Ph, the reduced imine groups are stabilized. This also gives electrochemical access to a [Ni(R 2 PhenTAA)] 2- species. DFT and TD-DFT calculations corroborate these findings and further illustrate the unique donor-acceptor properties of the respective OPD and imine moieties. The novel [Ni(R 2 PhenTAA)] complexes exhibit up to five different ligand-based oxidation states and are electrochemically stable in a range from -2.4 to +1.8 V for the Me/Ph complexes (vs Fc/Fc + ).

Aromatic amines are ubiquitous moieties in organic molecules and their direct functionalization is of great interest in many research areas due to their prevalence in pharmaceuticals and organic electronics. While several synthetic tools exist for the ortho- and para-functionalization of anilines, the functionalization of the less reactive meta-position is not easy to achieve with current methods. To date, the meta-C-H arylation of aniline derivatives has been restricted to either the use of directing groups & templates, or their transformation into anilides & quaternary anilinium salts. Herein, we report the first general and efficient meta-C-H-arylation of non-directed aniline derivatives via cooperative catalysis with a palladium-S,O-ligand-norbornene system. The reaction proceeds under mild conditions with a wide range of aniline derivatives and aryl iodides, while being operationally simple and scalable. Our preliminary mechanistic investigation-including the isolation of several palladium complexes and deuterium experiments-reveal useful insights into the substituent-effects of both the aniline-substrate and the norbornene-mediator during the meta-C-H activation step., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The replacement of palladium catalysts for Wacker-type oxidation of olefins into ketones by first-row transition metals is a relevant approach for searching more sustainable protocols. Besides highly sophisticated iron catalysts, all the other first-row transition metal complexes have only led to poor activities and selectivities. Herein, we show that the cobalt-tetraphenylporphyrin complex is a competent catalyst for the aerobic oxidation of styrenes into ketones with silanes as the hydrogen sources. Remarkably, under room temperature and air atmosphere, the reactions were exceedingly fast (up to 10 minutes) with a low catalyst loading (1 mol %) while keeping an excellent chemo- and Markovnikov-selectivity (up to 99 % of ketone). Unprecedently high TOF (864 h -1 ) and TON (5,800) were reached for the oxidation of aromatic olefins under these benign conditions. Mechanistic studies suggest a reaction mechanism similar to the Mukaiyama-type hydration of olefins with a change in the last fundamental step, which controls the chemoselectivity, thanks to a unique hydrogen bonding network between the ethanol solvent and the cobalt peroxo intermediate., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We show that the incorporation of a biotinylated Co(TAML) cofactor within streptavidin enables asymmetric radical-type oxygen atom transfer catalysis with improved activity and enantioselectivity.

The thermal curing of industrial coatings (e.g., car painting and metal coil coatings) is accompanied by a substantial energy consumption due to the intrinsically high temperatures required during the curing process. Therefore, the development of new photochemical curing processes-preferably using visible light-is in high demand. This work describes new diazo-based cross-linkers that can be used to photocure acrylic coatings using blue light. This work demonstrates that the structure of the tethered diazo compounds influences the cross-linking efficiency, finding that side reactions are suppressed upon engineering greater molecular flexibility. Importantly, this work shows that these diazo compounds can be employed as either thermal or photochemical cross-linkers, exhibiting identical crosslinking performances. The performance of diazo-cross-linked coatings is evaluated to reveal excellent water resistance and demonstrably similar material properties to UV-cured acrylates. These studies pave the way for further usage of diazo-functionalized cross-linkers in the curing of paints and coatings., (© 2023 The Authors. Macromolecular Rapid Communications published by Wiley-VCH GmbH.)

The importance of transition metal catalysis is exemplified by its wide range of applications, for example in the synthesis of chemicals, natural products, and pharmaceuticals. However, one relatively new application is for carrying out new-to-nature reactions inside living cells. The complex environment of a living cell is not welcoming to transition metal catalysts, as a diverse range of biological components have the potential to inhibit or deactivate the catalyst. Here we review the current progress in the field of transition metal catalysis, and evaluation of catalysis efficiency in living cells and under biological (relevant) conditions. Catalyst poisoning is a ubiquitous problem in this field, and we propose that future research into the development of physical and kinetic protection strategies may provide a route to improve the reactivity of catalysts in cells., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

In this contribution, we describe a post-assembly modification approach to selectively coordinate transition metals in Pd 12 L 24 cuboctahedra. The herein reported approach involves the preparation of Pd 12 L 24 nanospheres with protonated nitrogen donor ligands that are covalently linked at the interior. The so obtained Pd 12 (LH + ) 24 nanospheres are shown to be suitable for coordinative post-modification after deprotection by deprotonation. Selective formation of tetra-coordinated M B in Pd 12 M B 6 L 24 , tri-coordinated M B in Pd 12 M B 8 L 24 nanospheres and two-coordinated M B in Pd 12 M B 12 L 24 nanospheres is achieved as a result of different nitrogen donor ligands. A combination of pulsed EPR spectroscopy (DEER) to measure Cu-Cu distances in the different spheres, NMR studies and computational investigations, support the presence of the complexes at precise locations of the Pd 12 M B 6 L 24 nanosphere. The general post-assembly modification methodology can be extended using other transition metal precursors or supramolecular systems and can guide precise formation and investigation of novel transition metal-complex containing nanospheres with well-defined composition., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Immobilizing molecular catalysts on electrodes is vital for electrochemical applications. However, creating robust electrode-catalyst interactions while maintaining good catalytic performance and rapid electron transfer is challenging. Here, without introducing any foreign elements, we show a bottom-up synthetic approach of constructing the conjugated C-C bond between the commercial Vulcan carbon electrode and an organometallic catalyst. Characterization results from FTIR, XPS, aberration-corrected TEM and EPR confirmed the successful and uniform heterogenization of the complex. The synthesized Vulcan-LN 4 -Co catalyst is highly active and selective in the oxygen reduction reaction in neutral media, showing an 80 % hydrogen peroxide selectivity and a 0.72 V (vs. RHE) onset potential which significantly outperformed the homogenous counterpart. Based on single-crystal XRD and NMR data, we built a model for density functional theory calculations which showed a nearly optimal binding energy for the *OOH intermediate. Our results show that the direct conjugated C-C bonding is an effective approach for heterogenizing molecular catalysts on carbon, opening new opportunities for employing molecular catalysts in electrochemical applications., (© 2023 The Authors. ChemSusChem published by Wiley-VCH GmbH.)