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Proteomic investigations result in high dimensional datasets, but integration or comparison of different studies is hampered by high variances due to different experimental setups. In addition, cell culture conditions can have a huge impact on the outcome. This study systematically investigates the impact of experimental parameters on the proteomic profiles of commonly used cell lines-A549, differentiated THP-1 macrophage-like cells, and NR8383-for toxicity studies. The work focuses on analyzing the influence at the proteome level of cell culture setup involving different vessels, cell passage numbers, and post-differentiation harvesting time, aiming to improve the reliability of proteomic analyses for hazard assessment. Mass-spectrometry-based proteomics was utilized for accurate protein quantification by means of a label-free approach. Our results showed that significant proteome variations occur when cells are cultivated under different setups. Further analysis of these variations revealed their association to specific cellular pathways related to protein misfolding, oxidative stress, and proteasome activity. Conversely, the influence of cell passage numbers on the proteome is minor, suggesting a reliable range for conducting reproducible biological replicates. Notable, substantial proteome alterations occur over-time post-differentiation of dTHP-1 cells, particularly impacting pathways crucial for macrophage function. This finding is key for the interpretation of experimental results. These results highlight the need for standardized culture conditions in proteomic-based evaluations of treatment effects to ensure reliable results, a prerequisite for achieving regulatory acceptance of proteomics data., (© 2024. The Author(s).)

Using a diverse array of thermally robust phosphine enediyne ligands (dxpeb, X = Ph, Ph- p OCH 3 , Ph- p CF 3 , Ph- m 2 CH 3 , Ph- m 2 CF 3 , i Pr, Cy, and t Bu) a novel suite of cisplatin-like Pt(ii) metalloenediynes (3, Pt(dxpeb)Cl 2 ) has been synthesized and represents unique electronic perturbations on thermal Bergman cyclization kinetics. Complexes 3e (Ph- m 2 CF 3 ) and 3f ( i Pr) are the first of this structure type to be crystallographically characterized with inter alkyne termini distances (3e: 3.13 Å; 3f: 3.10 Å) at the lower end of the widely accepted critical distance range within which enediynes should demonstrate spontaneous ambient temperature cyclization. Despite different electronic profiles, these metalloenediynes adopt a rigid, uniform structure suggesting complexes of the form Pt(dxpeb)Cl 2 have orthogonalized geometric and electronic contributions to thermal Bergman cyclization. Kinetic activation parameters determined using 31 P NMR spectroscopy highlight the dramatic reactivity and thermal tunability of these complexes. At room temperature, the half-life ( t 1/2 ) of cyclization spans a range of ∼35 hours and for the aryl phosphine derivatives, cycloaromatization rates are 10-30 times faster for complexes with electron donating substituents (3b: Ph- p OCH 3 ; 3d: Ph- m 2 CH 3 ) compared to those with electron withdrawing substituents (3c: Ph- p CF 3 ; 3e: Ph- m 2 CF 3 ). Computational interrogation of the aryl phosphine metalloenediynes 3a-3e reveals that the origin of this precise electronic control derives from electronic withdrawing group-mediated alkyne carbon polarization that amplifies coulombic repulsion increasing the cyclization barrier height. Additionally, mixing between the in-plane π-orbitals and the phosphine aryl ring system is pronounced for complexes with electron donating substituents which stabilizes the developing C-C bond and lowers the activation barrier. This π-orbital mixing is negligible however, for complexes with electron withdrawing substituents due to an energetic mismatch of the orbital systems. Overall, this work demonstrates that for geometrically rigid frameworks, even remote enediyne functionalization can have pronounced effects on activation barrier., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Nitroso compounds, R-N=O, are common intermediates in organic synthesis, and are typically amenable to storage and manipulation at ambient temperature under aerobic conditions. By contrast, phosphorus-containing analogues, such as R-P=O (R = OH, CH 3 , OCH 3 , Ph), are extremely reactive and need to be studied in inert gas matrices at ultralow temperatures (3-15 K). These species are believed to be key intermediates in the degradation/combustion of organic phosphorus compounds, a class of chemicals that includes chemical warfare agents and flame retardants. Here we describe the isolation of a two-coordinate phosphorus(III) oxide under ambient conditions, enabled by the use of an extremely bulky amine ligand. Reactivity studies reveal that the phosphorus centre can be readily oxidized, and that in doing so, the P-O bond remains intact, an observation that is of interest to the proposed reactivity of transient phosphorus(III) oxides., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Despite their potential relevance as molecular models for industrial and biological catalysis, well-defined mononuclear iron carbide complexes are unknown, in part due to the limited number of appropriate C 1 synthons. Here, we show the ability of the cyaphide anion (C≡P - ) to serve as a C 1 source. The high spin ( S = 2) cyaphide complex PhB( t BuIm) 3 Fe-C≡P (PhB( t BuIm) 3 - = phenyl(tris(3- tert -butylimidazol-2-ylidene)borate) is readily accessed using the new cyaphide transfer reagent [Mg( Dipp NacNac)(CP)] 2 ( Dipp NacNac = CH{C(CH 3 )N(Dipp)} 2 and Dipp = 2,6-di(iso-propyl)phenyl). Phosphorus atom abstraction is effected by the three-coordinate Mo(III) complex Mo(N t BuAr) 3 (Ar = 3,5-Me 2 C 6 H 3 ), which produces the known phosphide ( t BuArN) 3 Mo≡P along with a transient iron carbide complex PhB( t BuIm) 3 Fe≡C. Electronic structure calculations reveal that PhB( t BuIm) 3 Fe≡C adopts a doublet ground state with nonzero spin density on the carbide ligand. While isolation of this complex is thwarted by rapid dimerization to afford the corresponding diiron ethynediyl complex, the carbide can be intercepted by styrene to provide an iron alkylidene.

Aim(s): This study reports on the implementation of a registered advanced nurse practitioner intervention. Aims include improving access, service user outcomes and integration between primary and secondary care., Design: This paper reports the quantitative results of a mixed methods implementation study. Qualitative data are reported separately. The PARiHS framework informs the implementation process itself, with considerations for nurses and other healthcare professionals explored., Methods: The CORE-OM 34 item rating scale was administered both pre- and post-intervention. Service user attendances in secondary care was monitored., Results: Findings suggest that the intervention was associated with clinically significant improvements in global or generic distress, reported by service users, as evidenced by changes in the CORE-OM scores. Access to care was recorded at an average of 3.6 days. Implementation science supported effective and safe implementation with clear governance structures., Conclusion: Registered advanced nurse practice in mental health clinics which provide full episodes of care results in improved integration and may be associated with positive patient outcomes. Implementation science is taught on Irish nursing programmes and this is important if innovative services are to be embedded in the healthcare system., Impact: The development of a model of care for mental health Registered Advanced Nurse Practitioners at the interface of primary and secondary care settings may be merited. Positive Advanced Recovery Connections may be associated with improving mental health outcomes and bolstering integration of primary and secondary care services. The utilisation of implementation science highlights the need for collaboration with all stakeholders to overcome barriers and recognise facilitators to attain the necessary model of integrated care., Patient and Public Contribution: Peer recovery input was provided by members of the service Recovery College, with participation evident in all stages of the project. The psychosocial assessment template was also co-designed., (© 2024 The Author(s). Journal of Advanced Nursing published by John Wiley & Sons Ltd.)

Steric manipulation is a known concept in molecular recognition but there is currently no linear free energy relationship correlating sterics to the stability of receptor-anion complexes nor to the reactivity of the bound anion. By analogy to Tolman cone angles in cation coordination chemistry, we explore how to define and correlate cone angles of organo-trifluoroborates (R-BF 3 - ) to the affinities observed for cyanostar-anion binding. We extend the analogy to a rare investigation of the anion's reactivity and how it changes upon binding. The substituent on the anion is used to define the cone angle, θ. A series of 10 anions were studied including versions with ethynyl, ethylene, and ethyl substituents to tune steric bulk across the sp, sp 2 and sp 3 hybridized α-carbons bearing 0, 1 and 2 hydrogen atoms. A linear relationship between affinity and cone angle is observed for anions bearing substituents larger than the -BF 3 - headgroup. This correlation predicted affinities of two new anions to within ±5 %. We explored how complexation affects the reactivity of fluoride exchange. The yield of fluoride transfer from R-BF 3 - to Lewis acid triphenylborane is correlated with cone angle. We predict that other rigid macrocycles, like commercially available bambusuril, could follow these trends., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Circularly polarized luminescence (CPL) from chiral molecules is attracting much attention due to its potential use in optical materials. However, formulation of CPL emitters as molecular solids typically deteriorates photophysical properties in the aggregated state leading to quenching and unpredictable changes in CPL behavior impeding materials development. To circumvent these shortcomings, a supramolecular approach can be used to isolate cationic dyes in a lattice of cyanostar-anion complexes that suppress aggregation-caused quenching and which we hypothesize can preserve the synthetically-crafted chiroptical properties. Herein, we verify that supramolecular assembly of small-molecule ionic isolation lattices (SMILES) allows translation of molecular ECD and CPL properties to solids. A series of cationic helicenes that display increasing chiroptical response is investigated. Crystal structures of three different packing motifs all show spatial isolation of dyes by the anion complexes. We observe the photophysical and chiroptical properties of all helicenes are seamlessly translated to water soluble nanoparticles by the SMILES method. Also, a DMQA helicene is used as FRET acceptor in SMILES nanoparticles of intensely absorbing rhodamine antennae to generate an 18-fold boost in CPL brightness. These features offer promise for reliably accessing bright materials with programmable CPL properties., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The reaction of equimolar trimethylsilyldiazomethyllithium (LiTMSD) with high spin ( S = 2) PhB(AdIm) 3 FeCl (PhB(AdIm) 3 - = tris(3-adamantylimidazol-2-ylidene)phenylborate) affords the corresponding N- nitrilimido complex PhB(AdIm) 3 Fe-N═N═C(SiMe 3 ). This complex can be converted to the thermodynamically more favorable C -isocyanoamido isomer PhB(AdIm) 3 Fe-C═N═N(SiMe 3 ) by reaction with an additional equivalent of LiTMSD. While the iron(II) complexes are four-coordinate, the diazomethane is bound side-on in the iron(I) congener PhB(AdIm) 3 Fe( N , N '-κ 2 -N 2 C(H)Si(CH 3 ) 3 ). The latter complex adopts high spin ( S = 3/2) ground state and features an unusually weak C-H bond. Photolysis of the iron(II) complexes induces N═N bond cleavage, with the iron(II) cyanide PhB(AdIm) 3 Fe-C≡N and iron(IV) nitride PhB(AdIm) 3 Fe≡N complexes being the major products of the reaction. The same products are obtained when the iron(I) complex is photolyzed or treated with a fluoride source. The trimethylsilyldiazomethane-derived ligand disassembly reactions are contrasted with those observed for related tris(carbene)amine complexes.

Proteomic investigations yield high-dimensional datasets, yet their application to large-scale toxicological assessments is hindered by reproducibility challenges due to fluctuating measurement conditions. To address these limitations, this study introduces an advanced tandem mass tag (TMT) labeling protocol. Although labeling approaches shorten data acquisition time by multiplexing samples compared to traditional label-free quantification (LFQ) methods in general, the associated costs may surge significantly with large sample sets, for example, in toxicological screenings. However, the introduced advanced protocol offers an efficient, cost-effective alternative, reducing TMT reagent usage (by a factor of ten) and requiring minimal biological material (1 µg), while demonstrating increased reproducibility compared to LFQ. To demonstrate its effectiveness, the advanced protocol is employed to assess the toxicity of nine benchmark nanomaterials (NMs) on A549 lung epithelial cells. While LFQ measurements identify 3300 proteins, they proved inadequate to reveal NM toxicity. Conversely, despite detecting 2600 proteins, the TMT protocol demonstrates superior sensitivity by uncovering alterations induced by NM treatment. In contrast to previous studies, the introduced advanced protocol allows simultaneous and straightforward assessment of multiple test substances, enabling prioritization, ranking, and grouping for hazard evaluation. Additionally, it fosters the development of New Approach Methodologies (NAMs), contributing to innovative methodologies in toxicological research., (© 2024 The Author(s). Small Methods published by Wiley‐VCH GmbH.)

Insect monitoring is essential to design effective conservation strategies, which are indispensable to mitigate worldwide declines and biodiversity loss. For this purpose, traditional monitoring methods are widely established and can provide data with a high taxonomic resolution. However, processing of captured insect samples is often time-consuming and expensive, which limits the number of potential replicates. Automated monitoring methods can facilitate data collection at a higher spatiotemporal resolution with a comparatively lower effort and cost. Here, we present the Insect Detect DIY (do-it-yourself) camera trap for non-invasive automated monitoring of flower-visiting insects, which is based on low-cost off-the-shelf hardware components combined with open-source software. Custom trained deep learning models detect and track insects landing on an artificial flower platform in real time on-device and subsequently classify the cropped detections on a local computer. Field deployment of the solar-powered camera trap confirmed its resistance to high temperatures and humidity, which enables autonomous deployment during a whole season. On-device detection and tracking can estimate insect activity/abundance after metadata post-processing. Our insect classification model achieved a high top-1 accuracy on the test dataset and generalized well on a real-world dataset with captured insect images. The camera trap design and open-source software are highly customizable and can be adapted to different use cases. With custom trained detection and classification models, as well as accessible software programming, many possible applications surpassing our proposed deployment method can be realized., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Sittinger et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

We report a neutral high-spin diradical of chiral C 2 -symmetric bis[5]diazahelicene with Δ E ST ≈ 0.4 kcal mol -1 , as determined by EPR spectroscopy/SQUID magnetometry. The diradical is the most persistent among all high-spin aminyl radicals reported to date by a factor of 20, with a half-life of up to 6 days in 2-MeTHF at room temperature. Its triplet ground state and excellent persistence may be associated with the unique spin density distribution within the dihydrophenazine moiety, which characterizes two effective 3-electron C-N bonds analogous to the N-O bond of a nitroxide radical. The enantiomerically enriched (ee ≥ 94%) ( MM )- and ( PP )-enantiomers of the precursors to the diradicals are obtained by either preparative chiral supercritical fluid chromatography or resolution via functionalization with the chiral auxiliary of the C 2 -symmetric racemic tetraamine. The barrier for the racemization of the solid tetraamine is Δ G ‡ = 43 ± 0.01 kcal mol -1 in the 483-523 K range. The experimentally estimated lower limit of the barrier for the racemization of a diradical, Δ G ‡ ≥ 26 kcal mol -1 in 2-MeTHF at 293 K, is comparable to the DFT-determined barrier of Δ G ‡ = 31 kcal mol -1 in the gas phase at 298 K. While the enantiomerically pure tetraamine displays strong chiroptical properties, with anisotropy factor | g | = |Δε|/ε = 0.036 at 376 nm, | g | ≈ 0.005 at 548 nm of the high-spin diradical is comparable to that recently reported triplet ground-state diradical dication. Notably, the radical anion intermediate in the generation of diradical exhibits a large SOMO-HOMO inversion, SHI = 35 kcal mol -1 .

The Fiber Pathogenicity Paradigm (FPP) establishes connections between fiber structure, durability, and disease-causing potential observed in materials like asbestos and synthetic fibers. While emerging nanofibers are anticipated to exhibit pathogenic traits according to the FPP, their nanoscale diameter limits rigidity, leading to tangling and loss of fiber characteristics. The absence of validated rigidity measurement methods complicates nanofiber toxicity assessment. By comprehensively analyzing 89 transcriptomics and 37 proteomics studies, this study aims to enhance carbon material toxicity understanding and proposes an alternative strategy to assess morphology-driven toxicity. Carbon materials are categorized as non-fibrous, high aspect ratio with shorter lengths, tangled, and rigid fibers. Mitsui-7 serves as a benchmark for pathogenic fibers. The meta-analysis reveals distinct cellular changes for each category, effectively distinguishing rigid fibers from other carbon materials. Subsequently, a robust random forest model is developed to predict morphology, unveiling the pathogenicity of previously deemed non-pathogenic NM-400 due to its secondary structures. This study fills a crucial gap in nanosafety by linking toxicological effects to material morphology, in particular regarding fibers. It demonstrates the significant impact of morphology on toxicological behavior and the necessity of integrating morphological considerations into regulatory frameworks., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The prevalence of anion-cation contacts in biomolecular recognition under aqueous conditions suggests that ionic interactions should dominate the binding of anions in solvents across both high and low polarities. Investigations of this idea using titrations in low polarity solvents are impaired by interferences from ion pairing that prevent a clear picture of binding. To address this limitation and test the impact of ion-ion interactions across multiple solvents, we quantified chloride binding to a cationic receptor after accounting for ion pairing. In these studies, we created a chelate receptor using aryl-triazole CH donors and a quinolinium unit that directs its cationic methyl inside the binding pocket. In low-polarity dichloromethane, the 1 : 1 complex (log K 1 : 1 ~ 7.3) is more stable than neutral chelates, but fortuitously comparable to a preorganized macrocycle (log K 1 : 1 ~ 6.9). Polar acetonitrile and DMSO diminish stabilities of the charged receptor (log K 1 : 1 ~ 3.7 and 1.9) but surprisingly 100-fold more than the macrocycle. While both receptors lose stability by dielectric screening of electrostatic stability, the cationic receptor also pays additional costs of organization. Thus even though the charged receptor has stronger binding in apolar solvents, the uncharged receptor has more anion affinity in polar solvents., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Supramolecular dimers are elementary units allowing the build-up of multi-molecule architectures. New among these are cyanostar-stabilized dimers of phosphate and phosphonate anions. While the anion dimerization at the heart of these assemblies is reliable, the covalent synthesis leading to this class of designer anions serves as a bottleneck in the pathway to supramolecular assemblies. Herein, we demonstrate the reliable synthesis of 14 diverse anionic monomers by Heck coupling between vinyl phosphonic acid and aryl bromide compounds. When this synthesis is combined with reliable anion dimerization, we show formation of supramolecular dimers and polymers by co-assembly with cyanostar macrocycles. The removal of the covalent bottleneck opened up a seamless synthetic route to iterate through three monomers affording the solubility needed to characterize the mechanism of supramolecular polymerization. We also test the idea that the small size of these vinyl phosphonates provide identical dimer stabilities across the library by showing how mixtures of anions undergo statistical (social) self-sorting. We exploit this property by preparing soluble copolymers from the mixing of different monomers. This multi-anion assembly shows the utility of a library for programming properties., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)

We report complex formation between the chloroacetamide 2,6-diazaadamantane nitroxide radical (ClA-DZD) and cucurbit[7]uril (CB-7), for which the association constant in water, K a M 6 M -1 , is at least 1 order of magnitude higher than the previously studied organic radicals. The radical is highly immobilized by CB-7, as indicated by the increase in the rotational correlation time, τ rot , by a factor of 36, relative to that in the buffer solution. The X-ray structure of ClA-DZD@CB-7 shows the encapsulated DZD guest inside the undistorted CB-7 host, with the pendant group protruding outside. Upon addition of CB-7 to T4 Lysozyme (T4L) doubly spin-labeled with the iodoacetamide derivative of DZD, we observe the increase in τ rot and electron spin coherence time, T m , along with the narrowing of interspin distance distributions. Sensitivity of the DEER measurements at 83 K increases by a factor 4-9, compared to the common spin label such as MTSL, which is not affected by CB-7. Interspin distances of 3 nm could be reliably measured in water/glycerol up to temperatures near the glass transition/melting temperature of the matrix at 200 K, thus bringing us closer to the goal of supramolecular recognition-enabled long-distance DEER measurements at near physiological temperatures. The X-ray structure of DZD-T4L 65 at 1.12 Å resolution allows for unambiguous modeling of the DZD label (0.88 occupancy), indicating an undisturbed structure and conformation of the protein.

Iron sulfur clusters are critical to a plethora of biological processes; however, little is known about the elementary unit of these clusters, namely the [Fe=S] n+ fragment. Here, we report the synthesis and characterization of a terminal iron sulfido complex. Despite its high spin ( S = 5/2) ground state, structural, spectroscopic, and computational characterization provide evidence for iron sulfur multiple bond character. Intriguingly, the complex reacts with additional sulfur to afford an S = 3/2 iron(III) disulfido (S 2 2- ) complex. Preliminary studies reveal that the sulfido complex reacts with dihydroanthracene to afford an iron(II) hydrosulfido complex, akin to the reactivity of iron oxo complexes. By contrast, there is no reaction with the disulfido complex. These results provide important insight into the nature of the iron sulfide unit., Competing Interests: DECLARATION OF INTERESTS The authors declare no competing interests.

Open-shell organic molecules, including S = 1/2 radicals, may provide enhanced properties for several emerging technologies; however, relatively few synthesized to date possess robust thermal stability and processability. We report the synthesis of S = 1/2 biphenylene-fused tetrazolinyl radicals 1 and 2 . Both radicals possess near-perfect planar structures based on their X-ray structures and density-functional theory (DFT) computations. Radical 1 possesses outstanding thermal stability as indicated by the onset of decomposition at 269 °C, based on thermogravimetric analysis (TGA) data. Both radicals possess very low oxidation potentials <0 V (vs. SCE) and their electrochemical energy gaps, E cell ≈ 0.9 eV, are rather low. Magnetic properties of polycrystalline 1 are characterized by superconducting quantum interference device (SQUID) magnetometry revealing a one-dimensional S = 1/2 antiferromagnetic Heisenberg chain with exchange coupling constant J '/ k ≈ -22.0 K. Radical 1 in toluene glass possesses a long electron spin coherence time, T m ≈ 7 μs in the 40-80 K temperature range, a property advantageous for potential applications as a molecular spin qubit. Radical 1 is evaporated under ultrahigh vacuum (UHV) forming assemblies of intact radicals on a silicon substrate, as confirmed by high-resolution X-ray photoelectron spectroscopy (XPS). Scanning electron microscope (SEM) images indicate that the radical molecules form nanoneedles on the substrate. The nanoneedles are stable for at least 64 hours under air as monitored by using X-ray photoelectron spectroscopy. Electron paramagnetic resonance (EPR) studies of the thicker assemblies, prepared by UHV evaporation, indicate radical decay according to first-order kinetics with a long half-life of 50 ± 4 days at ambient conditions.

Two-coordinate silylamido complexes of nickel and copper rapidly react with CO 2 to selectively form a new cyanate ligand along with hexamethyldisiloxane byproducts. Mechanistic insight into these reactions was obtained from the synthesis of proposed intermediates, several silyl- and phenyl- substituted amido analogues, and their subsequent reactivity with CO 2 . These studies suggest that a unique intramolecular double silyl transfer step facilitates CO 2 deoxygenation, which likely contributes to the rapid rates of reaction. The deoxygenation reactions create a platform for a synthetic cycle in which copper amido complexes convert CO 2 to organic silylcarbamates.

The nitride ligand in the iron(IV) complex PhB( i Pr 2 Im) 3 Fe≡N reacts with boron hydrides to afford PhB( i Pr 2 Im) 3 FeN( B )H ( B = 9-BBN ( 1 ), Bpin ( 2 )) and with (Bpin) 2 to afford PhB( i Pr 2 Im) 3 FeN(Bpin) 2 ( 3 ). The iron(II) borylamido products have all been structurally and spectroscopically characterized, demonstrating facile insertion into B-H and B-B bonds by PhB( i Pr 2 Im) 3 Fe≡N. Density functional theory (DFT) calculations reveal that the quintet state ( S = 2) is significantly lower in energy than the singlet ( S = 0) and triplet ( S = 1) states for all products. Stoichiometric reaction with (Bpin) 2 does not produce the mono-borylated iron imido species PhB( i Pr 2 Im) 3 FeN(Bpin). DFT calculations suggest that this is because PhB( i Pr 2 Im) 3 FeN(Bpin) is unstable toward disproportionation to the starting iron(IV) nitride and PhB( i Pr 2 Im) 3 FeN(Bpin) 2 . Attempts at B-C bond insertion using phenyl- and benzyl-pinacol borane were unsuccessful, which we attribute to unfavorable kinetics.

Aspects of the proposed pathway combining chain-end and enantiomorphic site control for the stereospecific polymerization of lactide (LA) were investigated through studies of aluminum complexes supported by enantiopure and racemic bipyrrolidine-based salan ligands, Lig 1 AlOBn and Lig 2 AlOBn. Spectroscopic analysis of stoichiometric initiation reactions and the definition of the stereochemistry of the selective formation of the "match" single-insertion products by X-ray crystallography led to key conclusions about the observed stereocontrol. Notably, it was determined to rely heavily on the preference for the trio of stereocenters around the metal to have a "match" formation ( RR -ligand + S -polymer), which works synergistically with the enantiomorphic site preference of the catalyst to ring-open next to a stereocenter of a monomer of the same chirality as that of the ligand, resulting in highly heterotactic or syndiotactic PLA from rac - or meso -LA, respectively.

The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R-BF 3 - ). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R-BF 3 - , by cyanostar macrocycles that are size-complementary to the inorganic BF 4 - progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K + salts of R-BF 3 - anions., (© 2022 Wiley-VCH GmbH.)

We report high-spin aminyl triradicals with near-planar triphenylene backbones. Near-planarity of the fused aminyl radicals and the 2,6,10-triphenylene ferromagnetic coupling unit (FCU), magnetically equivalent to three fused 3,4'-biphenyl FCUs, assures an effective 2p π -2p π overlap within the cross-conjugated π-system, leading to an S = 3/2 (quartet) ground state that is well separated from low-spin excited doublet states. Thermal populations of the low-spin ( S = 1/2) excited states are detectable both by SQUID magnetometry and electron paramagnetic resonance (EPR) spectroscopy, providing doublet-quartet energy gaps, Δ E DQ , corresponding to >85% population of the quartet ground states at room temperature. Notably, EPR-based determination of Δ E DQ relies on direct detection of the quartet ground state and doublet excited states. The Δ E DQ values are 1.0-1.1 kcal mol -1 , with the more sterically shielded triradical having the larger value. The half-life of the more sterically shielded triradical in 2-methyltetrahydrofuran (2-MeTHF) is about 6 h at room temperature. The less sterically shielded triradical in 2-MeTHF decomposes at 158 K with a half-life of about 4 h, while at 195 K, the half-life is still about 2 h. The dominant products of the decay of triradicals are the corresponding triamines, suggesting hydrogen atom abstraction from the solvent as the primary mechanism. This study expands the frontier of the open-shell PAHs/nanographenes, of which the unique electronic, nonlinear optical, and magnetic properties could be useful in the development of novel organic electronics, photonics, and spintronics.

Herein, we report the reactions of an Fe(II) imido complex [Ph 2 B( t BuIm) 2 Fe═NDipp] - ( 1 ) with internal alkynes and isobutyronitrile, affording the Fe amido allenyl complexes [Ph 2 B( t BuIm) 2 Fe(NHDipp)((R 1 )C═C═C(R 2 )(H))] - (R 1 = Et or n Pr; R 2 = Me or Et, 2-5 ) and the Fe amido keteniminate complex [Ph 2 B( t BuIm) 2 Fe(NHDipp)(N═C═CMe 2 )K(THF)] n ( 8-K ), respectively. These transformations represent the previously unknown ene-like reactivity of a metal-ligand multiple bond. Stoichiometric reactions of 2 and 8-K with DippNH 2 lead to the regeneration of 3-hexyne and isobutyronitrile, respectively, with concomitant formation of the bis(anilido) complex [Ph 2 B( t BuIm) 2 Fe(NHDipp) 2 ] - ( 9 ). These results provide the platform for 1 as an efficient catalyst for the selective α-deuteration of nitriles and alkynes by RND 2 . These results demonstrate a new reaction mode for metal imido complexes and suggest new avenues for using the imido ligand in catalysis.

X-ray photoemission spectroscopy (XPS) has been used to examine the interaction between Au and HfS 3 at the Au/HfS 3 interface. XPS measurements reveal dissociative chemisorption of O 2 , leading to the formation of an oxide of Hf at the surface of HfS 3 . This surface hafnium oxide, along with the weakly chemisorbed molecular species, such as O 2 and H 2 O, are likely responsible for the observed p-type characteristics of HfS 3 reported elsewhere. HfS 3 devices exhibit n-type behaviour if measured in vacuum but turn p-type in air. Au thickness-dependent XPS measurements provide clear evidence of band bending as the S 2p and Hf 4f core-level peak binding energies for Au/HfS 3 are found to be shifted to higher binding energies. This band bending implies formation of a Schottky-barrier at the Au/HfS 3 interface, which explains the low measured charge carrier mobilities of HfS 3 -based devices. The transistor measurements presented herein also indicate the existence of a Schottky barrier, consistent with the XPS core-level binding energy shifts, and show that the bulk of HfS 3 is n-type.

Triplet ground-state organic molecules are of interest with respect to several emerging technologies but usually show limited stability, especially as thin films. We report an organic diradical, consisting of two Blatter radicals, that possesses a triplet ground state with a singlet-triplet energy gap, Δ E ST ≈ 0.4-0.5 kcal mol -1 (2 J / k ≈ 220-275 K). The diradical possesses robust thermal stability, with an onset of decomposition above 264 °C (TGA). In toluene/chloroform, glassy matrix, and fluid solution, an equilibrium between two conformations with Δ E ST ≈ 0.4 kcal mol -1 and Δ E ST ≈ -0.7 kcal mol -1 is observed, favoring the triplet ground state over the singlet ground-state conformation in the 110-330 K temperature range. The diradical with the triplet ground-state conformation is found exclusively in crystals and in a polystyrene matrix. The crystalline neutral diradical is a good electrical conductor with conductivity comparable to the thoroughly optimized bis(thiazolyl)-related monoradicals. This is surprising because the triplet ground state implies that the underlying π-system is cross-conjugated and thus is not compatible with either good conductance or electron delocalization. The diradical is evaporated under ultra-high vacuum to form thin films, which are stable in air for at least 18 h, as demonstrated by X-ray photoelectron and electron paramagnetic resonance (EPR) spectroscopies.

The presence of redox innocent metal ions has been proposed to modulate the reactivity of metal ligand multiple bonds; however, insight from structure/function relationships is limited. Here, alkali metal reduction of the Fe(III) imido complex [Ph 2 B( t BuIm) 2 Fe═NDipp] ( 1 ) provides the series of structurally characterized Fe(II) imido complexes [Ph 2 B( t BuIm) 2 Fe═NDippLi(THF) 2 ] ( 2 ), [Ph 2 B( t BuIm) 2 Fe═NDippNa(THF) 3 ] ( 3 ), and [Ph 2 B( t BuIm) 2 Fe═NDippK] 2 ( 4 ), in which the alkali metal cations coordinate the imido ligand. Structural investigations demonstrate that the alkali metal ions modestly lengthen the Fe═N bond distance from that in the charge separated complex [Ph 2 B( t BuIm) 2 Fe═NDipp][K(18-C-6)THF 2 ] ( 5 ), with the longest bond observed for the smallest alkali metal ion. In contrast to 5 , the imido ligands in 2 - 4 can be protonated and alkylated to afford Fe(II) amido complexes. Combined experimental and computational studies reveal that the alkali metal polarizes the Fe═N bond, and the basicity of imido ligand increases according to 5 < 4 ≈ 3 < 2 . The basicity of the imido ligands influences the relative rates of reaction with 1,4-cyclohexadiene, specifically by gating access to complex 5 , which is the species that is active for HAT. All complexes 2 - 4 react with benzophenone form metastable Fe(II) intermediates that subsequently eliminate the metathesis product Ph 2 C═NDipp, with relative rates dependent on the alkali metal ion. By contrast, the same reaction with 5 does not lead to the formation of Ph 2 C═NDipp. These results demonstrate that the coordination of alkali metal ions dictate both the structure and reactivity of the imido ligand and moreover can direct the reactivity of reaction intermediates.

The risk of each nanoform (NF) of the same substance cannot be assumed to be the same, as they may vary in their physicochemical characteristics, exposure and hazard. However, neither can we justify a need for more animal testing and resources to test every NF individually. To reduce the need to test all NFs, (regulatory) information requirements may be fulfilled by grouping approaches. For such grouping to be acceptable, it is important to demonstrate similarities in physicochemical properties, toxicokinetic behaviour, and (eco)toxicological behaviour. The GRACIOUS Framework supports the grouping of NFs, by identifying suitable grouping hypotheses that describe the key similarities between different NFs. The Framework then supports the user to gather the evidence required to test these hypotheses and to subsequently assess the similarity of the NFs within the proposed group. The evidence needed to support a hypothesis is gathered by an Integrated Approach to Testing and Assessment (IATA), designed as decision trees constructed of decision nodes. Each decision node asks the questions and provides the methods needed to obtain the most relevant information. This White paper outlines existing and novel methods to assess similarity of the data generated for each decision node, either via a pairwise analysis conducted property-by-property, or by assessing multiple decision nodes simultaneously via a multidimensional analysis. For the pairwise comparison conducted property-by-property we included in this White paper: The x-fold, Bayesian and Arsinh-OWA distance algorithms performed comparably in the scoring of similarity between NF pairs. The Euclidean distance was also useful, but only with proper data transformation. The x-fold method does not standardize data, and thus produces skewed histograms, but has the advantage that it can be implemented without programming knowhow. A range of multidimensional evaluations, using for example dendrogram clustering approaches, were also investigated. Multidimensional distance metrics were demonstrated to be difficult to use in a regulatory context, but from a scientific perspective were found to offer unexpected insights into the overall similarity of very different materials. In conclusion, for regulatory purposes, a property-by-property evaluation of the data matrix is recommended to substantiate grouping, while the multidimensional approaches are considered to be tools of discovery rather than regulatory methods., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

There has been an increasing interest in chemistry involving nitrogen oxyanions, largely due to the environmental hazards associated with increased concentrations of these anions leading to eutrophication and aquatic "dead zones". Herein, we report the synthesis and characterization of a suite of MNO x complexes (M = Co, Zn: x = 2, 3). Reductive deoxygenation of cobalt bis(nitrite) complexes with bis(boryl)pyrazine is faster for cobalt than previously reported nickel, and pendant O-bound nitrito ligand is still readily deoxygenated, despite potential implication of an isonitrosyl primary product. Deoxygenation of zinc oxyanion complexes is also facile, despite zinc being unable to stabilize a nitrosyl ligand, with liberation of nitric oxide and nitrous oxide, indicating N-N bond formation. X-ray photoelectron spectroscopy is effective for discriminating the types of nitrogen in these molecules. ESI mass spectrometry of a suite of M(NO x ) y ( x = 2, 3 and y = 1, 2) shows that the primary form of ionization is loss of an oxyanion ligand, which can be alleviated via the addition of tetrabutylammonium (TBA) as a nonintuitive cation pair for the neutral oxyanion complexes. We have shown these complexes to be subject to deoxygenation, and there is evidence for nitrogen oxyanion reduction in several cases in the ESI plume. The attractive force between cation and neutral is explored experimentally and computationally and attributed to hydrogen bonding of the nitrogen oxyanion ligands with ammonium α-CH 2 protons. One example of ESI-induced reductive dimerization is mimicked by bulk solution synthesis, and that product is characterized by X-ray diffraction to contain two Co(NO) 2 + groups linked by a highly conjugated diazapolyene.

The iron oxo unit, [Fe=O] n + is a critical intermediate in biological oxidation reactions. While its higher oxidation states are well studied, relatively little is known about the least-oxidized form [Fe III =O] + . Here, the thermally stable complex PhB(AdIm) 3 Fe=O has been structurally, spectroscopically, and computationally characterized as a bona fide iron(III) oxo. An unusually short Fe-O bond length is consistent with iron-oxygen multiple bond character and is supported by electronic structure calculations. The complex is thermally stable yet is able to perform hydrocarbon oxidations, facilitating both C-O bond formation and dehydrogenation reactions., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Here, we report a one-pot solvothermal method for the development of magnetically recoverable catalysts with Ru or Ag nanoparticles (NPs) capped by chitosan (CS), a derivative of natural chitin. The formation of iron oxide NPs was carried out in situ in the presence of CS and iron acetylacetonate in boiling triethyleneglycol (TEG) due to CS solubilization in warm TEG. Coordination with Ru or Ag species and the NP formation take place in the same reaction solution, eliminating intermediate steps. In optimal conditions the method developed allows stabilization of 2.2 nm monodisperse Ru NPs (containing both Ru 0 and Ru 4+ species) that are evenly distributed through the catalyst, while for Ag NPs, this stabilizing medium is inferior, leading to exceptionally large Ag nanocrystals. Catalytic testing of CS-Ru magnetically recoverable catalysts in the reduction of 4-nitrophenol to 4-aminophenol with excess NaBH 4 revealed that the catalyst with 2.2 nm Ru NPs exhibits the highest catalytic activity compared to samples with larger Ru NPs (2.9-3.2 nm). Moreover, this catalyst displayed extraordinary shelf-life in the aqueous solution (up to ten months) and excellent reusability in ten consecutive reactions with easy magnetic separation at each step which were assigned to its conformational rigidity at a constant pH. These characteristics as well as favorable environmental factors of the catalyst fabrication, make it promising for nitroarene reduction., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Synthesis of bis-spiro-oxetane and bis-spiro-tetrahydrofuran pyrroline nitroxide radicals relies on the Mitsunobu reaction-mediated double cyclizations of N -Boc protected pyrroline tetraols. Structures of the nitroxide radicals are supported by X-ray crystallography. In a trehalose/sucrose matrix at room temperature, the bis-spiro-oxetane nitroxide radical possesses electron spin coherence time, T m ≈ 0.7 μs. The observed enhanced T m is most likely associated with strong hydrogen bonding of oxetane moieties to the trehalose/sucrose matrix.

The reaction chemistry of the bis-tetrazinyl pyridine ligand (btzp) towards nitrogen oxyanions coordinated to zinc is studied in order to explore the reduction of the NO x - substrates with a redox-active ligand in the absence of redox activity at the metal. Following syntheses and characterization of (btzp)ZnX 2 for X=Cl, NO 3 and NO 2 , featuring O-Zn linkage of both nitrogen oxyanions, it is shown that a silylating agent selectively delivers silyl substituents to tetrazine nitrogens, without reductive deoxygenation of NO x -1 . A new synthesis of the highly hydrogenated H 4 btzp, containing two dihydrotetrazine reductants is described as is the synthesis and characterization of (H 4 btzp)ZnX 2 for X=Cl and NO 3 , both of which show considerable hydrogen bonding potential of the dihydrotetrazine ring NH groups. The (H 4 btzp)ZnCl 2 complex does not bind zinc in the pincer pocket, but instead H 4 btzp becomes a bridge between neighboring atoms through tetrazine nitrogen atoms, forming a polymeric chain. The reaction of AgNO 2 with (H 4 btzp)ZnCl 2 is shown to proceed with fast nitrite deoxygenation, yielding water and free NO. Half of the H 4 btzp reducing equivalents form Ag 0 and thus the chloride ligand remains coordinated to the zinc metal center to yield (btzp)ZnCl 2 . To compare with AgNO 2 , experiments of (H 4 btzp)ZnCl 2 with NaNO 2 result in salt metathesis between chloride and nitrite, highlighting the importance of a redox-active cation in the reduction of nitrite to NO., (© 2021 Wiley-VCH GmbH.)

The syntheses of (DIM)Ni(NO 3 ) 2 and (DIM)Ni(NO 2 ) 2 , where DIM is a 1,4-diazadiene bidentate donor, are reported to enable testing of bis boryl reduced N-heterocycles for their ability to carry out stepwise deoxygenation of coordinated nitrate and nitrite, forming O(Bpin) 2 . Single deoxygenation of (DIM)Ni(NO 2 ) 2 yields the tetrahedral complex (DIM)Ni(NO)(ONO), with a linear nitrosyl and κ 1 -ONO. Further deoxygenation of (DIM)Ni(NO)(ONO) results in the formation of dimeric [(DIM)Ni(NO)] 2 , where the dimer is linked through a Ni-Ni bond. The lost reduced nitrogen byproduct is shown to be N 2 O, indicating N-N bond formation in the course of the reaction. Isotopic labelling studies establish that the N-N bond of N 2 O is formed in a bimetallic Ni 2 intermediate and that the two nitrogen atoms of (DIM)Ni(NO)(ONO) become symmetry equivalent prior to N-N bond formation. The [(DIM)Ni(NO)] 2 dimer is susceptible to oxidation by AgX (X = NO 3 - , NO 2 - , and OTf - ) as well as nitric oxide, the latter of which undergoes nitric oxide disproportionation to yield N 2 O and (DIM)Ni(NO)(ONO). We show that the first step in the deoxygenation of (DIM)Ni(NO)(ONO) to liberate N 2 O is outer sphere electron transfer, providing insight into the organic reductants employed for deoxygenation. Lastly, we show that at elevated temperatures, deoxygenation is accompanied by loss of DIM to form either pyrazine or bipyridine bridged polymers, with retention of a BpinO - bridging ligand., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Toxicological studies propose that exposure to carbon black nanoparticles induces organ injuries and inflammatory responses. Besides, current understanding of the molecular mechanisms implies that carbon black nanoparticles (CBNP) exposure induces the production of reactive oxygen species (ROS) causing inflammation, mitochondrial dysfunction or disturbance in calcium homeostasis. However, the precise mechanisms whereby CBNP exert these effects in the lung are still not fully understood. To gain insight into the possible mechanism of CBNP exerted toxicity, human alveolar epithelial cells (A549) were exposed to different concentrations of CBNP and for different timepoints. The reaction of the cells was monitored by the systematic use of cell-based measurements of calcium and ROS, in the presence and absence of calcium (Ca 2+ ) pump inhibitors/chelators and antioxidants. Followed by an in-depth PCR analysis of 84 oxidative stress-related genes. The measurements revealed, as compared to the control, that exposure to CBNP nanoparticles leads to the generation of high ROS levels, as well as a disturbance in calcium homeostasis, which remained primarily unchanged even after 24 h of exposure. Nevertheless, in presence of antioxidants N-acetylcysteine (NAC) and Trolox, ROS formation was considerably reduced without affecting the intracellular calcium concentration. On the other hand, Ca 2+ pump inhibitors/chelators, BAPTA (1,2-bis(o-amino phenoxy)ethane-N, N, N', N'-tetraacetic acid) and verapamil not only decreased the Ca 2+ overload, but also further decreased the ROS formation, indicating its role in CBNP-induced oxidative stress. Further, a PCR array analysis of A549 cells in presence and absence of the calmodulin (CaM) antagonist W7, indicated toward nine altered oxidative stress-related genes which further confirmed our cytotoxicity results. Obtained data suggested that CBNP exposure elevates calcium ion concentration, which further contributes to oxidative stress, via the calcium-binding protein CaM. Its inhibition with W7 leads to downregulation in gene expression of nine oxidative stress-related genes, which otherwise, as compared to control, show increased gene expression. The results of the study thus confirm that exposure of lung epithelial cells to CBNP leads to oxidative stress; however, the oxidative stress itself is a result of a disturbance in both calcium and ROS homeostasis, and should be considered while searching for a new strategy for prevention of CBNP-induced lung toxicity.

Background: People are exposed to mixtures containing allergens and irritants often causing contact dermatitis. Therefore, regulatory authorities require systematic information on the effects of mixtures on the sensitization threshold. In this study a moderate (cinnamal) and a weak (ethylene glycol dimethacrylate) allergen were combined with irritants covering different mechanisms of action (sodium dodecyl sulfate, salicylic acid, and α-pinene). For a systematic approach, the single substances were initially tested using the KeratinoSens assay. Thereafter, each allergen was combined with noncytotoxic concentrations of the irritants., Method: The KeratinoSens assay was applied for the single substances according to OECD (Organisation for Economic Co-operation and Development) Test Guideline 442D. Based on these results, three noncytotoxic concentrations of the irritants were selected and applied simultaneously with 12 concentrations of the allergens to the KeratinoSens cells. Sensitization threshold and cytotoxicity were measured and compared with the individual testing., Results: The combinations of allergens and irritants differed from the effects of the single substances and lowered the sensitization threshold. The quantitative approach allowed a clear description of the changes which varied by factors between 1.1 and 10.3., Conclusions: Overall, the allergen was the prominent compound in the mixture and its nature appeared to determine the degree of the response., (© 2020 The Authors. Contact Dermatitis published by John Wiley & Sons Ltd.)

High-spin ( S = 3/2) organic triradicals may offer enhanced properties with respect to several emerging technologies, but those synthesized to date typically exhibit small doublet quartet energy gaps and/or possess limited thermal stability and processability. We report a quartet ground state triradical 3 , synthesized by a Pd(0)-catalyzed radical-radical cross-coupling reaction, which possesses two doublet-quartet energy gaps, Δ E DQ ≈ 0.2-0.3 kcal mol -1 and Δ E DQ 2 ≈ 1.2-1.8 kcal mol -1 . The triradical has a 70+% population of the quartet ground state at room temperature and good thermal stability with onset of decomposition at >160 °C under an inert atmosphere. Magnetic properties of 3 are characterized by SQUID magnetometry in polystyrene glass and by quantitative EPR spectroscopy. Triradical 3 is evaporated under ultrahigh vacuum to form thin films of intact triradicals on silicon substrate, as confirmed by high-resolution X-ray photoelectron spectroscopy. AFM and SEM images of the ∼1 nm thick films indicate that the triradical molecules form islands on the substrate. The films are stable under ultrahigh vacuum for at least 17 h but show onset of decomposition after 4 h at ambient conditions. The drop-cast films are less prone to degradation in air and have a longer lifetime.

Reduction of the three-coordinate iron(III) imido [Ph 2 B( t BuIm) 2 Fe═NDipp] ( 1 ) affords [Ph 2 B( t BuIm) 2 Fe═NDipp][K(18-C-6)THF 2 ] ( 2 ), a rare example of a high-spin ( S = 2) iron(II) imido complex. Unusually for a late metal imido complex, the imido ligand in 2 has nucleophilic character, as demonstrated by the reaction with DippNH 2 , which establishes an equilibrium with the bis(anilido) complex [Ph 2 B( t BuIm) 2 Fe(NHDipp) 2 ][K(18-C-6)THF 2 ] ( 3 ). In an unusual transformation, formal insertion of i PrN═C═N i Pr into the Fe═N(imido) bond yields the guanidinate [Ph 2 B( t BuIm) 2 Fe( i PrN) 2 CNDipp][K(18-C-6)THF 2 ] ( 4 ). Reaction of 4 with excess DippNH 2 provides 3 , along with the guanidine ( i PrNH) 2 C═NDipp. As suggested by these stoichiometric reactions, 2 is an efficient catalyst for the guanylation of carbodiimides, converting a wide range of aniline substrates under mild conditions.

Double deprotonation of the salt [Ph 2 B(PMe 3 ) 2 ][OTf] ( 1 ) provides access to a bis(ylide)diphenylborate ligand that is readily transferred in situ to iron(II). Depending on the reaction stoichiometry, both the "ate" complex [Ph 2 B(Me 2 PCH 2 ) 2 Fe(μ-Cl) 2 Li(THF) 2 ] ( 2 ) and the homoleptic complex [Ph 2 B(Me 2 PCH 2 ) 2 ] 2 Fe( 3 ) can be prepared from FeCl 2 (THF) 1.5 . Further reaction of 3 with FeCl 2 (THF) 1.5 produces the chloride-bridged dimer [Ph 2 B(Me 2 PCH 2 ) 2 Fe(μ-Cl) 2 Fe(CH 2 PMe 2 ) 2 BPh 2 ]( 4 ). Attempts to reduce or alkylate 4 provide 3 as the only isolable product, likely a consequence of the low steric hindrance of the bis(ylide)diphenylborate ligand. On the other hand, reaction of 4 with the strong field ligand CN t Bu provides the six-coordinate, diamagnetic complex [Ph 2 B(Me 2 PCH 2 ) 2 Fe(CN t Bu) 4 ][Cl]( 5 ). Electronic structure calculations for the bis(ylide)diphenylborate ligand and homoleptic complex 3 suggest that the C(ylide) atoms are strong σ-donors with little π-bonding character. These initial results suggest the potential for this bis(ylide)diphenylborate ligand in coordination chemistry.

High-valent iron species are key intermediates in oxidative biological processes, but hexavalent complexes apart from the ferrate ion are exceedingly rare. Here, we report the synthesis and structural and spectroscopic characterization of a stable Fe(VI) complex ( 3 ) prepared by facile one-electron oxidation of an Fe(V) bis(imido) ( 2 ). Single-crystal x-ray diffraction of 2 and 3 revealed four-coordinate Fe centers with an unusual "seesaw" geometry. 57 Fe Mössbauer, x-ray photoelectron, x-ray absorption, and electron-nuclear double resonance (ENDOR) spectroscopies, supported by electronic structure calculations, support a low-spin ( S = 1/2) d 3 Fe(V) configuration in 2 and a diamagnetic ( S = 0) d 2 Fe(VI) configuration in 3 Their shared seesaw geometry is electronically dictated by a balance of Fe-imido σ- and π-bonding interactions., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Introduction: The benchmark dose (BMD) is a dose that produces a predetermined change in the response rate of an adverse effect. This approach is increasingly utilized to analyze quantitative dose-response relationships. To proof this concept, statistical analysis was compared with the BMD approach in order to rank the sensitivity as well as the toxicity and to describe the mode of action., Methods: Bronchial (BEAS-2B) and alveolar epithelial cells (A549) were exposed to a wide concentration range (0.4-100 μg/mL) of five metal oxide nanoparticles (CeO 2 , CuO, TiO 2 , ZnO, ZrO 2 ). Eight toxicity endpoints were determined representing integrity of lysosomal and cell membrane, oxidative stress level, glutathione based detoxification (glutathione S-transferase), oxidative metabolism (cytochrome P450), alteration of the mitochondrial membrane potential, alteration of phase II antioxidative enzyme (NAD(P)H:quinone oxidoreductase), and de novo DNA synthesis., Results: Based on the BMD calculated for the most sensitive test, the toxicity decreased in the following order: ZnO > CuO > TiO 2 >ZrO 2 >CeO 2 in BEAS-2B. Both statistical evaluation methods revealed a higher sensitivity of BEAS-2B cells. The BMD-derived mode of action for CuO confirmed the existing hypotheses and provided insights into less known mechanisms., Conclusion: The findings proofed that BMD analysis is an effective tool to evaluate different aspects of risk assessment., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The N 2 analogue phosphorus nitride (PN) was the first phosphorus-containing compound to be detected in the interstellar medium; however, this thermodynamically unstable compound has a fleeting existence on Earth. Here, we show that reductive coupling of iron(IV) nitride and molybdenum(VI) phosphide complexes assembles PN as a bridging ligand in a structurally characterized bimetallic complex. Reaction with C≡N t Bu releases the mononuclear complex [(N 3 N)Mo-PN] - , N 3 N = [(Me 3 SiNCH 2 CH 2 ) 3 N] 3- ), which undergoes light-induced linkage isomerization to provide [(N 3 N)Mo-NP] - , as revealed by photocrystallography. While structural and spectroscopic characterization, supported by electronic structure calculations, reveals the PN multiple bond character, coordination to molybdenum induces a nucleophilic character at the terminal atom of the PN/NP ligands. Indeed, the linkage isomers can be trapped in solution by reaction with a Rh(I) electrophile., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

This study focuses on a homework program where an Australian University partnered with a school to support children from culturally and linguistically diverse backgrounds. Undergraduate tutors, paired with a child each semester, provided weekly learning support. This exploratory study aimed to understand the experiences of the children participating in the program and any benefits received. Nineteen children participated in activity-based focus groups, and seven undergraduate tutors participated in one-on-one interviews. Overarching themes identified were as follows: making homework club enjoyable, program outcomes, tutor-child relationship and transitioning to a new tutor. Although children were required to do homework they usually avoided, the task was made less onerous and even enjoyable because of the relationship the children had with their tutor, the support received and new skills learnt. The tutor-child relationship was deeply valued, with the tutor's role going beyond instructional support to also providing social and emotional support and a sense of belonging in line with Social Support Theory. Both the children and tutors expressed contrasting views about the experience of children transitioning to a new tutor each semester and this departs from the extant literature. The challenges related to the loss of connection, while positive aspects concerned the opportunity to make new friends and learn from different teaching styles. Given these contrasting findings, it is worth considering how the transition process can be managed and explained to children and increase the chances of positive adaptation. Despite the relatively short-term nature of the tutor-child relationship, the children expressed clear academic, social and emotional benefits. The findings suggest that semester-based university-school homework tutoring programs can be effective despite their short-term nature, provided due consideration is given to the transition process. These findings address the paucity of research exploring short-term programs of this nature., (© 2020 John Wiley & Sons Ltd.)

Here, we report the structures and properties of biocatalysts based on glucose oxidase (GOx) macromolecules immobilized on the mesoporous zirconia surface with or without magnetic iron oxide nanoparticles (IONPs) in zirconia pores. Properties of these biocatalysts were studied in oxidation of d-glucose to d-gluconic acid at a wide range of pH and temperatures. We demonstrate that the calcination temperature (300, 400, or 600 °C) of zirconia determines its structure, with crystalline materials obtained at 400 and 600 °C. This, in turn, influences the catalytic behavior of immobilized GOx, which was tentatively assigned to the preservation of GOx conformation on the crystalline support surface. IONPs significantly enhance the biocatalyst activity due to synergy with the enzyme. At the same time, neither support porosity nor acidity/basicity shows correlations with the properties of this biocatalyst. The highest relative activity of 98% (of native GOx) at a pH 6-7 and temperature of 40-45 °C was achieved for the biocatalyst based on ZrO 2 calcined at 600 °C and containing IONPs. This process is green as it is characterized by a high atom economy due to the formation of a single product with high selectivity and conversion and minimization of waste due to magnetic separation of the catalyst from an aqueous solution. These and an exceptional stability of this catalyst in 10 consecutive reactions (7% relative activity loss) make it favorable for practical applications., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

We demonstrate a host-guest molecular recognition approach to advance double electron-electron resonance (DEER) distance measurements of spin-labeled proteins. We synthesized an iodoacetamide derivative of 2,6-diazaadamantane nitroxide (DZD) spin label that could be doubly incorporated into T4 Lysozyme (T4L) by site-directed spin labeling with efficiency up to 50% per cysteine. The rigidity of the fused ring structure and absence of mobile methyl groups increase the spin echo dephasing time ( T m ) at temperatures above 80 K. This enables DEER measurements of distances >4 nm in DZD-labeled T4L in glycerol/water at temperatures up to 150 K with increased sensitivity compared to that of a common spin label such as MTSL. Addition of β-cyclodextrin reduces the rotational correlation time of the label, slightly increases T m , and most importantly, narrows (and slightly lengthens) the interspin distance distributions. The distance distributions are in good agreement with simulated distance distributions obtained by rotamer libraries. These results provide a foundation for developing supramolecular recognition to facilitate long-distance DEER measurements at near physiological temperatures.

Two electron-reduction of the Ti IV guanidinate complex (Im Dipp N)( Xyket guan)TiCl 2 gives (η 6 -Im Dipp N)( xyket guan)Ti (1 intra ) and (Im Dipp N)( Xyket guan)Ti(η 6 -C 6 H 6 ) (1 inter ) ( Xyket guan=[(tBuC=N)C(NXylyl) 2 ] - , Xylyl=2,5-dimethylphenyl) in the absence or presence of benzene, respectively. These complexes have been found to hydrogenate monocyclic and polycyclic arenes under relatively mild conditions (150 psi, 80 °C)-the first example of catalytic, homogeneous arene hydrogenation with TON >1 by a Group IV system., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Sequence-controlled supramolecular polymers offer new design paradigms for generating stimuli-responsive macromolecules with enhanced functionalities. The dynamic character of supramolecular links present challenges to sequence definition in extended supramolecular macromolecules, and design principles remain nascent. Here, we demonstrate the first example of using stoichiometry-control to specify the monomer sequence in a linear supramolecular polymer by synthesizing both a homopolymer and an alternating copolymer from the same glycol-substituted cyanostar macrocycle and phenylene-linked diphosphate monomers. A 2:1 stoichiometry between macrocycle and diphosphate produces a supramolecular homopolymer of general formula ( A ) n comprised of repeating units of cyanostar-stabilized phosphate-phosphate dimers. Using a 1:1 stoichiometry, an alternating ( AB ) n structure is produced with half the phosphate dimers now stabilized by the additional counter cations that emerge hierarchically after forming the stronger cyanostar-stabilized phosphate dimers. These new polymer materials and binding motifs are sufficient to bear normal and shear stress to promote significant and tunable adhesive properties. The homopolymer ( A ) n , consisting of cyanostar-stabilized anti -electrostatic linkages, shows adhesion strength comparable to commercial superglue formulations based on polycyanoacrylate but is thermally reversible. Unexpectedly, and despite including traditional ionic linkages, the alternating copolymer ( AB ) n shows weaker adhesion strength more similar to commercial white glue based on poly(vinyl acetate). Thus, the adhesion properties can be tuned over a wide range by simply controlling the stoichiometric ratio of monomers. This study offers new insight into supramolecular polymers composed of custom-designed anion and receptor monomers and demonstrates the utility of emerging functional materials based on anion-anion linkages.

Amines are ubiquitous in the chemical industry and are present in a wide range of biological processes, motivating the development of amine-sensitive sensors. There are many turn-on amine sensors, however there are no examples of turn-on sensors that utilize the amine's ability to react by single electron transfer (SET). We investigated a new turn-on amine probe with a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) fluorophore. BODIPY fluorescence is first preprogrammed into an off state by internal photoinduced electron transfer (PET) to an electron-deficient quinolinium ring, resulting in fluorescence quenching. At low concentrations of aliphatic amine (0 to 10 mM), this PET pathway is shut down by external SET from the amine to the photoexcited charge-transfer state of the probe and the fluorescence is turned on. At high concentrations of amine (50 mM to 1 M), we observed collisional quenching of the BODIPY fluorescence. The probe is selective for aliphatic amines over aromatic amines, and aliphatic thiols or alcohols. The three molecular processes modulate the BODIPY fluorescence in a multi-mechanistic way with two of them producing a direct response to amine concentrations. The totality of the three molecular processes produced the first example of a multi-state and dose-responsive amine sensor.

The paramagnetic cyano-bridged complex PhB( t BuIm) 3 Fe-NC-Mo(N t BuAr) 3 (Ar = 3,5-Me 2 C 6 H 3 ) is readily assembled from a new four-coordinate, high-spin ( S = 2) iron(II) monocyanide complex and the three-coordinate molybdenum(III) complex Mo(N t BuAr) 3 . X-ray diffraction and IR spectroscopy reveal that delocalization of unpaired electron density into the cyanide π* orbitals leads to a reduction of the C-N bond order. Direct current (dc) magnetic susceptibility measurements, supported by electronic structure calculations, demonstrate the presence of strong antiferromagnetic exchange between spin centers, with a coupling constant of J = -122(2) cm -1 . To our knowledge, this value represents the strongest magnetic exchange coupling ever to be observed through cyanide. These results demonstrate the ability of low-coordinate metal fragments to engender extremely strong magnetic exchange coupling through cyanide by virtue of significant π-backbonding into the cyanide ligand.

Elevated intracellular levels of reactive oxygen species (ROS), e.g. resulting from exposure to xenobiotics, can cause severe damages. Antioxidant defence mechanisms, which involve regulation of enzyme activities, protect cells to a certain extent. Nevertheless, continuous or increased exposure can overwhelm this system resulting in an adverse cellular state. To simulate exposure scenarios and to investigate the transition to an adverse cellular state, a mathematical model for the dynamics of ROS in response to xenobiotic-induced oxidative stress has been developed. It is based on exposure experiments of human urothelial cells (RT4) to the nitrated polycyclic aromatic hydrocarbon 3-nitrobenzanthrone (3-NBA), a component of diesel engine exhaust, and takes into account the following metabolic pathways of the antioxidant defence system: glutathione redox cycle scavenging directly ROS, the pentose phosphate pathway and the gluconate shunt as NADPH supplier and the beginning of glycolysis. In addition, ROS generation due to the bioactivation of 3-NBA has been implemented. The regulation of enzyme activities plays an important role in the presented mathematical model. The in silico model consists of ordinary differential equations on the basis of enzyme kinetics and mass action for the metabolism of 3-NBA. Parameters are either estimated from performed in vitro experiments via least-squares fitting or obtained from the literature. The results underline the importance of the pentose phosphate pathway to cope with oxidative stress and suggest an important role of the gluconate shunt during low-dose exposure.