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1.	Allum, F., et al. (författare) A localized view on molecular dissociation via electron-ion partial covariance 2022 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5:1 Tidskriftsartikel (refereegranskat)abstract Inner-shell photoelectron spectroscopy provides an element-specific probe of molecular structure, as core-electron binding energies are sensitive to the chemical environment. Short-wavelength femtosecond light sources, such as Free-Electron Lasers (FELs), even enable time-resolved site-specific investigations of molecular photochemistry. Here, we study the ultraviolet photodissociation of the prototypical chiral molecule 1-iodo-2-methylbutane, probed by extreme-ultraviolet (XUV) pulses from the Free-electron LASer in Hamburg (FLASH) through the ultrafast evolution of the iodine 4d binding energy. Methodologically, we employ electron-ion partial covariance imaging as a technique to isolate otherwise elusive features in a two-dimensional photoelectron spectrum arising from different photofragmentation pathways. The experimental and theoretical results for the time-resolved electron spectra of the 4d(3/2) and 4d(5/2) atomic and molecular levels that are disentangled by this method provide a key step towards studying structural and chemical changes from a specific spectator site. Coincidence experiments at free-electron lasers enable time resolved site-specific investigations of molecular photochemistry at high signal rates, but isolating individual dissociation processes still poses a considerable technical challenge. Here, the authors use electron-ion partial covariance imaging to isolate otherwise elusive chemical shifts in UV-induced photofragmentation pathways of the prototypical chiral molecule 1-iodo-2-methylbutane.
2.	Bettelli, Mercedes A., et al. (författare) Effects of multi-functional additives during foam extrusion of wheat gluten materials 2024 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 7:1 Tidskriftsartikel (refereegranskat)abstract To broaden the range in structures and properties, and therefore the applicability of sustainable foams based on wheat gluten expanded with ammonium-bicarbonate, we show here how three naturally ocurring multifunctional additives affect their properties. Citric acid yields foams with the lowest density (porosity of ~50%) with mainly closed cells. Gallic acid acts as a radical scavenger, yielding the least crosslinked/ aggregated foam. The use of a low amount of this acid yields foams with the highest uptake of the body-fluid model substance (saline, ~130% after 24 hours). However, foams with genipin show a large and rapid capillary uptake (50% in one second), due to their high content of open cells. The most dense and stiff foam is obtained with one weight percent genipin, which is also the most crosslinked. Overall, the foams show a high energy loss-rate under cyclic compression (84-92% at 50% strain), indicating promising cushioning behaviour. They also show a low compression set, indicating promising sealability. Overall, the work here provides a step towards using protein biofoams as a sustainable alternative to fossil-based plastic/rubber foams in applications where absorbent and/or mechanical properties play a key role.
3.	Boily, Jean-Francois, et al. (författare) Direct identification of reaction sites on ferrihydrite 2020 Ingår i: Communications Chemistry. - : Nature Publishing Group. - 2399-3669. ; 3:1 Tidskriftsartikel (refereegranskat)abstract Hydroxyl groups are the cornerstone species driving catalytic reactions on mineral nanoparticles of Earth's crust, water, and atmosphere. Here we directly identify populations of these groups on ferrihydrite, a key yet misunderstood iron oxyhydroxide nanomineral in natural sciences. This is achieved by resolving an enigmatic set of vibrational spectroscopic signatures of reactive hydroxo groups and chemisorbed water molecules embedded in specific chemical environments. We assist these findings by exploring a vast array of configurations of computer-generated nanoparticles. We find that these groups are mainly disposed along rows at edges of sheets of iron octahedra. Molecular dynamics of nanoparticles as large as 10 nm show that the most reactive surface hydroxo groups are predominantly free, yet are hydrogen bond acceptors in an intricate network formed with less reactive groups. The resolved vibrational spectroscopic signatures open new possibilities for tracking catalytic reactions on ferrihydrite, directly from the unique viewpoint of its reactive hydroxyl groups. Ferrihydrite nanoparticles have many hydroxyl sites which can react with environmental contaminants and nutrients, but the surface structure of this common mineral is still not fully understood. Here, a combination of vibrational spectroscopy and molecular simulations identify hydroxyl groups exposed along rows at the edges of sheets of iron octahedra.
4.	Brett, Calvin J., et al. (författare) Revealing structural evolution occurring from photo-initiated polymer network formation 2020 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 3:1 Tidskriftsartikel (refereegranskat)abstract Photopolymerization is a key enabling technology offering spatial and temporal control to allow for future functional materials to be made to meet societal needs. However, gaining access to robust experimental techniques to describe the evolution of nanoscale morphology in photo-initiated polymeric systems has proven so far to be a challenging task. Here, we show that these physical transformations can be monitored and quantified at the nanoscale in situ and in real-time. It is demonstrated that the initial structural features of the liquid precursors significantly affect the final morphology and the physical properties of the resulting solid via the occurrence of local heterogeneities in the molecular mobility during the curing transformation. We have made visible how local physical arrestings in the liquid, associated with both cross-linking and vitrification, determine the length scale of the local heterogeneities forming upon curing, found to be in the 10-200nm range. Acomplete account of the structural evolution occurring during photopolymerisation is lacking. Here the physical changes occurring on the nanometer scale during photopolymerisation of acrylates are followed over time by FTIR, X-ray reflectometry, AFM, and GISAXS, offering insight into the mechanism by which initial composition influences the final morphology.
5.	Bryant, Patrick, et al. (författare) Peptide binder design with inverse folding and protein structure prediction 2023 Ingår i: Communications Chemistry. - 2399-3669. ; 6:1 Tidskriftsartikel (refereegranskat)abstract The computational design of peptide binders towards a specific protein interface can aid diagnostic and therapeutic efforts. Here, we design peptide binders by combining the known structural space searched with Foldseek, the protein design method ESM-IF1, and AlphaFold2 (AF) in a joint framework. Foldseek generates backbone seeds for a modified version of ESM-IF1 adapted to protein complexes. The resulting sequences are evaluated with AF using an MSA representation for the receptor structure and a single sequence for the binder. We show that AF can accurately evaluate protein binders and that our bind score can select these (ROC AUC = 0.96 for the heterodimeric case). We find that designs created from seeds with more contacts per residue are more successful and tend to be short. There is a relationship between the sequence recovery in interface positions and the plDDT of the designs, where designs with >= 80% recovery have an average plDDT of 84 compared to 55 at 0%. Designed sequences have 60% higher median plDDT values towards intended receptors than non-intended ones. Successful binders (predicted interface RMSD <= 2 angstrom) are designed towards 185 (6.5%) heteromeric and 42 (3.6%) homomeric protein interfaces with ESM-IF1 compared with 18 (1.5%) using ProteinMPNN from 100 samples. Designing peptides that bind to specific protein targets is crucial for peptidic drug development, however, traditional computer-aided binder design is outperformed by AlphaFold2. Here, the authors develop a peptide binder designing tool by combining Foldseek, ESM-IF1 and AlphaFold2 to increase the success rate.
6.	Capezza, Antonio Jose, et al. (författare) Acylation of agricultural protein biomass yields biodegradable superabsorbent plastics 2021 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 4:1 Tidskriftsartikel (refereegranskat)abstract Superabsorbent polymers (SAP) are a central component of hygiene and medical products requiring high liquid swelling, but these SAP are commonly derived from petroleum resources. Here, we show that sustainable and biodegradable SAP can be produced by acylation of the agricultural potato protein side-stream (PPC) with a non-toxic dianhydride (EDTAD). Treatment of the PPC yields a material with a water swelling capacity of ca. 2400%, which is ten times greater than the untreated PPC. Acylation was also performed on waste potato fruit juice (PFJ), i.e. before the industrial treatment to precipitate the PPC. The use of PFJ for the acylation implies a saving of 320 000 tons as CO2 in greenhouse gas emissions per year by avoiding the industrial drying of the PFJ to obtain the PPC. The acylated PPC shows biodegradation and resistance to mould growth. The possibilities to produce a biodegradable SAP from the PPC allows for future fabrication of environment-friendly and disposable daily-care products, e.g. diapers and sanitary pads.
7.	Deiana, Marco, et al. (författare) Site-selected thionated benzothioxanthene chromophores as heavy-atom-free small-molecule photosensitizers for photodynamic therapy 2022 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 5 Tidskriftsartikel (refereegranskat)abstract Photodynamic therapy is a clinically approved anticancer modality that employs a light-activated agent (photosensitizer) to generate cytotoxic reactive oxygen species (ROS). There is therefore a growing interest for developing innovative photosensitizing agents with enhanced phototherapeutic performances. Herein, we report on a rational design synthetic procedure that converts the ultrabright benzothioxanthene imide (BTI) dye into three heavy-atom-free thionated compounds featuring close-to-unit singlet oxygen quantum yields. In contrast to the BTI, these thionated analogs display an almost fully quenched fluorescence emission, in agreement with the formation of highly populated triplet states. Indeed, the sequential thionation on the BTI scaffold induces torsion of its skeleton reducing the singlet-triplet energy gaps and enhancing the spin-orbit coupling. These potential PSs show potent cancer-cell ablation under light irradiation while remaining non-toxic under dark condition owing to a photo-cytotoxic mechanism that we believe simultaneously involves singlet oxygen and superoxide species, which could be both characterized in vitro. Our study demonstrates that this simple site-selected thionated platform is an effective strategy to convert conventional carbonyl-containing fluorophores into phototherapeutic agents for anticancer PDT.
8.	Dey, Ananta, et al. (författare) Exploiting hot electrons from a plasmon nanohybrid system for the photoelectroreduction of CO2 2024 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 7:1 Tidskriftsartikel (refereegranskat)abstract Plasmonic materials convert light into hot carriers and heat to mediate catalytic transformation. The participation of hot carriers (photocatalysis) remains a subject of vigorous debate, often argued on the basis that carriers have ultrashort lifetime incompatible with drive photochemical processes. This study utilises plasmon hot electrons directly in the photoelectrocatalytic reduction of CO2 to CO via a Ppasmonic nanohybrid. Through the deliberate construction of a plasmonic nanohybrid system comprising NiO/Au/ReI(phen-NH2)(CO)3Cl (phen-NH2 = 1,10-Phenanthrolin-5-amine) that is unstable above 580 K; it was possible to demonstrate hot electrons are the main culprit in CO2 reduction. The engagement of hot electrons in the catalytic process is derived from many approaches that cover the processes in real-time, from ultrafast charge generation and separation to catalysis occurring on the minute scale. Unbiased in situ FTIR spectroscopy confirmed the stepwise reduction of the catalytic system. This, coupled with the low thermal stability of the ReI(phen-NH2)(CO)3Cl complex, explicitly establishes plasmonic hot carriers as the primary contributors to the process. Therefore, mediating catalytic reactions by plasmon hot carriers is feasible and holds promise for further exploration. Plasmonic nanohybrid systems can leverage plasmon’s unique photophysics and capabilities because they expedite the carrier’s lifetime.
9.	El Omari, Kamel, et al. (författare) Experimental phasing opportunities for macromolecular crystallography at very long wavelengths 2023 Ingår i: Communications Chemistry. - : Nature Publishing Group. - 2399-3669. ; 6:1 Tidskriftsartikel (refereegranskat)abstract Despite recent advances in cryo-electron microscopy and artificial intelligence-based model predictions, a significant fraction of structure determinations by macromolecular crystallography still requires experimental phasing, usually by means of single-wavelength anomalous diffraction (SAD) techniques. Most synchrotron beamlines provide highly brilliant beams of X-rays of between 0.7 and 2 Å wavelength. Use of longer wavelengths to access the absorption edges of biologically important lighter atoms such as calcium, potassium, chlorine, sulfur and phosphorus for native-SAD phasing is attractive but technically highly challenging. The long-wavelength beamline I23 at Diamond Light Source overcomes these limitations and extends the accessible wavelength range to λ = 5.9 Å. Here we report 22 macromolecular structures solved in this extended wavelength range, using anomalous scattering from a range of elements which demonstrate the routine feasibility of lighter atom phasing. We suggest that, in light of its advantages, long-wavelength crystallography is a compelling option for experimental phasing.
10.	El-Zohry, Ahmed M., et al. (författare) Ultrafast transient infrared spectroscopy for probing trapping states in hybrid perovskite films 2022 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5:1 Tidskriftsartikel (refereegranskat)abstract Studying the charge dynamics of perovskite materials is a crucial step to understand the outstanding performance of these materials in various fields. Herein, we utilize transient absorption in the mid-infrared region, where solely electron signatures in the conduction bands are monitored without external contributions from other dynamical species. Within the measured range of 4000 nm to 6000 nm (2500–1666 cm−1), the recombination and the trapping processes of the excited carriers could be easily monitored. Moreover, we reveal that within this spectral region the trapping process could be distinguished from recombination process, in which the iodide-based films show more tendencies to trap the excited electrons in comparison to the bromide-based derivatives. The trapping process was assigned due to the emission released in the mid-infrared region, while the traditional band-gap recombination process did not show such process. Various parameters have been tested such as film composition, excitation dependence and the probing wavelength. This study opens new frontiers for the transient mid-infrared absorption to assign the trapping process in perovskite films both qualitatively and quantitatively, along with the potential applications of perovskite films in the mid-IR region.
11.	Fuller, Franklin D., et al. (författare) Resonant X-ray emission spectroscopy from broadband stochastic pulses at an X-ray free electron laser 2021 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 4:1 Tidskriftsartikel (refereegranskat)abstract X-ray absorption and X-ray free electron lasers are important tools to study chemical and structural dynamics, but spectral details like pre-edge features are inherently hard to detect. Here, the authors show that stochastic spectroscopy can yield similar spectral information to monochromatic spectroscopies, while increasing signal yield and reducing acquisition time. Hard X-ray spectroscopy is an element specific probe of electronic state, but signals are weak and require intense light to study low concentration samples. Free electron laser facilities offer the highest intensity X-rays of any available light source. The light produced at such facilities is stochastic, with spikey, broadband spectra that change drastically from shot to shot. Here, using aqueous ferrocyanide, we show that the resonant X-ray emission (RXES) spectrum can be inferred by correlating for each shot the fluorescence intensity from the sample with spectra of the fluctuating, self-amplified spontaneous emission (SASE) source. We obtain resolved narrow and chemically rich information in core-to-valence transitions of the pre-edge region at the Fe K-edge. Our approach avoids monochromatization, provides higher photon flux to the sample, and allows non-resonant signals like elastic scattering to be simultaneously recorded. The spectra obtained match well with spectra measured using a monochromator. We also show that inaccurate measurements of the stochastic light spectra reduce the measurement efficiency of our approach.
12.	Ganguly, Smita, et al. (författare) The origin of enhanced O2+ production from photoionized CO2 clusters 2022 Ingår i: Communications Chemistry. - 2399-3669. Tidskriftsartikel (refereegranskat)abstract CO2-rich planetary atmospheres are continuously exposed to ionising radiation driving major photochemical processes. In the Martian atmosphere, CO2 clusters are predicted to exist at high altitudes motivating a deeper understanding of their photochemistry. In this joint experimental-theoretical study, we investigate the photoreactions of CO2 clusters (≤2 nm) induced by soft X-ray ionisation. We observe dramatically enhanced production of O2- from photoionized CO2 clusters compared to the case of the isolated molecule and identify two relevant reactions. Using quantum chemistry calculations and multi-coincidence mass spectrometry, we pinpoint the origin of this enhancement: A size-dependent structural transition of the clusters from a covalently bonded arrangement to a weakly bonded polyhedral geometry that activates an exothermic reaction producing O+2. Our results unambiguously demonstrate that the photochemistry of small clusters/particles will likely have a strong influence on the ion balance in atmospheres.
13.	Gapsys, Vytautas, et al. (författare) Accurate absolute free energies for ligand-protein binding based on non-equilibrium approaches 2021 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 4 Tidskriftsartikel (refereegranskat)abstract Molecular dynamics-based approaches to calculate absolute protein-ligand binding free energy often rely on equilibrium free energy perturbation (FEP) protocols. Here, the authors study ligands binding to bromodomains and T4 lysozyme and find that both equilibrium and non-equilibrium approaches converge to the same results with the non-equilibrium method converging faster than FEP. The accurate calculation of the binding free energy for arbitrary ligand-protein pairs is a considerable challenge in computer-aided drug discovery. Recently, it has been demonstrated that current state-of-the-art molecular dynamics (MD) based methods are capable of making highly accurate predictions. Conventional MD-based approaches rely on the first principles of statistical mechanics and assume equilibrium sampling of the phase space. In the current work we demonstrate that accurate absolute binding free energies (ABFE) can also be obtained via theoretically rigorous non-equilibrium approaches. Our investigation of ligands binding to bromodomains and T4 lysozyme reveals that both equilibrium and non-equilibrium approaches converge to the same results. The non-equilibrium approach achieves the same level of accuracy and convergence as an equilibrium free energy perturbation (FEP) method enhanced by Hamiltonian replica exchange. We also compare uni- and bi-directional non-equilibrium approaches and demonstrate that considering the work distributions from both forward and reverse directions provides substantial accuracy gains. In summary, non-equilibrium ABFE calculations are shown to yield reliable and well-converged estimates of protein-ligand binding affinity.
14.	Gatchell, Michael, 1988-, et al. (författare) Open questions on the interaction dynamics of molecules and clusters in the gas phase 2022 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5 Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract Emerging experimental techniques combined with theoretical advances allow unprecedented studies of the dynamics of gas phase molecules and clusters induced in interactions with photons, electrons, or heavy particles. Here, the authors highlight recent advances, key open questions, and challenges in this field of research with focus on experimental studies of dynamics of ions stored on millisecond timescales and beyond, and its applications in astrochemistry and astronomy.
15.	Grånäs, Elin, et al. (författare) Role of hydroxylation for the atomic structure of a non-polar vicinal zinc oxide 2021 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 4:1 Tidskriftsartikel (refereegranskat)abstract From the catalytic, semiconducting, and optical properties of zinc oxide (ZnO) numerous potential applications emerge. For the physical and chemical properties of the surface, under-coordinated atoms often play an important role, necessitating systematic studies of their influence. Here we study the vicinal ZnO(10 1 ¯ 4) surface, rich in under-coordinated sites, using a combination of several experimental techniques and density functional theory calculations. We determine the atomic-scale structure and find the surface to be a stable, long-range ordered, non-polar facet of ZnO, with a high step-density and uniform termination. Contrary to an earlier suggested nano-faceting model, a bulk termination fits much better to our experimental observations. The surface is further stabilized by dissociatively adsorbed H2O on adjacent under-coordinated O- and Zn-atoms. The stabilized surface remains highly active for water dissociation through the remaining under-coordinated Zn-sites. Such a vicinal oxide surface is a prerequisite for future adsorption studies with atomically controlled local step and terrace geometry.
16.	Hakim, Charifa, et al. (författare) Understanding the redox process upon electrochemical cycling of the P2-Na0.78Co1/2Mn1/3Ni1/6O2 electrode material for sodium-ion batteries 2020 Ingår i: Communications Chemistry. - : NATURE PUBLISHING GROUP. - 2399-3669. ; 3 Tidskriftsartikel (refereegranskat)abstract The inclusion of nickel and manganese in layered sodium metal oxide cathodes for sodium ion batteries is known to improve stability, but the redox behaviour at high voltage is poorly understood. Here in situ X-ray spectroscopy studies show that the redox behaviour of oxygen anions can account for an increase in specific capacity at high voltages. Rechargeable sodium-ion batteries have recently attracted renewed interest as an alternative to Li-ion batteries for electric energy storage applications, because of the low cost and wide availability of sodium resources. Thus, the electrochemical energy storage community has been devoting increased attention to designing new cathode materials for sodium-ion batteries. Here we investigate P2- Na0.78Co1/2Mn1/3Ni1/6O2 as a cathode material for sodium ion batteries. The main focus is to understand the mechanism of the electrochemical performance of this material, especially differences observed in redox reactions at high potentials. Between 4.2 V and 4.5 V, the material delivers a reversible capacity which is studied in detail using advanced analytical techniques. In situ X-ray diffraction reveals the reversibility of the P2-type structure of the material. Combined soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering demonstrates that Na deintercalation at high voltages is charge compensated by formation of localized electron holes on oxygen atoms.
17.	Haziri, Veton, et al. (författare) A gateway for ion transport on gas bubbles pinned onto solids 2021 Ingår i: Communications Chemistry. - : Nature Publishing Group. - 2399-3669. ; 4:1 Tidskriftsartikel (refereegranskat)abstract Gas bubbles grown on solids are more than simple vehicles for gas transport. They are charged particles with surfaces populated with exchangeable ions. We here unveil a gateway for alkali metal ion transport between oxygen bubbles and semi-conducting (iron oxide) and conducting (gold) surfaces. This gateway was identified by electrochemical impedance spectroscopy using an ultramicroelectrode in direct contact with bubbles pinned onto these solid surfaces. We show that this gateway is naturally present at open circuit potentials, and that negative electric potentials applied through the solid enhance ion transport. In contrast, positive potentials or contact with an insulator (polytetrafluoroethylene) attenuates transport. We propose that this gateway is generated by overlapping electric double layers of bubbles and surfaces of contrasting (electro)chemical potentials. Knowledge of this ion transfer phenomenon is essential for understanding electric shielding and reaction overpotential caused by bubbles on catalysts. This has especially important ramifications for predicting processes including mineral flotation, microfluidics, pore water geochemistry, and fuel cell technology.
18.	Himo, Fahmi, et al. (författare) Status report on the quantum chemical cluster approach for modeling enzyme reactions 2022 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract The cluster approach is a very valuable technique for elucidating reaction mechanisms of enzymes. Here, the authors discuss the current status of this methodology, highlighting its strengths and weaknesses, and argue that it should be the method of choice for investigating enzymatic reaction mechanisms.
19.	Holmgaard List, Nanna, et al. (författare) Chemical control of excited-state reactivity of the anionic green fluorescent protein chromophore 2024 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 7:1 Tidskriftsartikel (refereegranskat)abstract Controlling excited-state reactivity is a long-standing challenge in photochemistry, as a desired pathway may be inaccessible or compete with other unwanted channels. An important example is internal conversion of the anionic green fluorescent protein (GFP) chromophore where non-selective progress along two competing torsional modes (P: phenolate and I: imidazolinone) impairs and enables Z-to-E photoisomerization, respectively. Developing strategies to promote photoisomerization could drive new areas of applications of GFP-like proteins. Motivated by the charge-transfer dichotomy of the torsional modes, we explore chemical substitution on the P-ring of the chromophore as a way to control excited-state pathways and improve photoisomerization. As demonstrated by methoxylation, selective P-twisting appears difficult to achieve because the electron-donating potential effects of the substituents are counteracted by inertial effects that directly retard the motion. Conversely, these effects act in concert to promote I-twisting when introducing electron-withdrawing groups. Specifically, 2,3,5-trifluorination leads to both pathway selectivity and a more direct approach to the I-twisted intersection which, in turn, doubles the photoisomerization quantum yield. Our results suggest P-ring engineering as an effective approach to boost photoisomerization of the anionic GFP chromophore. Controlling excited-state reactivity is a long-standing challenge in photochemistry, as desired pathways may be inaccessible or compete with unwanted channels, which is problematic for applications. Here, the authors show that 2,3,5-trifluorination on the phenolate ring of the green fluorescent protein chromophore leads to both pathway selectivity and doubles the photoisomerization quantum yield.
20.	Honda, Satoshi, et al. (författare) Organomediated polymerization 2024 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 7:1 Tidskriftsartikel (refereegranskat)abstract Communications Chemistry is pleased to introduce a Collection of articles focused on organomediated polymerization. Here, the Guest Editors highlight the themes within and look towards the future of this research field.
21.	Ideböhn, Veronica, 1992, et al. (författare) Symmetry breaking in core-valence double ionisation of allene 2023 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 6:1 Tidskriftsartikel (refereegranskat)abstract Allene serves as a model to study multiple ionization of organic molecules. Here, the authors use synchrotron radiation-based multi-particle coincidence techniques and high-level ab initio calculations to propose a simple physical model to elucidate the symmetry breaking in core-valence double ionization of allene. Conventional electron spectroscopy is an established one-electron-at-the-time method for revealing the electronic structure and dynamics of either valence or inner shell ionized systems. By combining an electron-electron coincidence technique with the use of soft X-radiation we have measured a double ionisation spectrum of the allene molecule in which one electron is removed from a C1s core orbital and one from a valence orbital, well beyond Siegbahns Electron-Spectroscopy-for-Chemical-Analysis method. This core-valence double ionisation spectrum shows the effect of symmetry breaking in an extraordinary way, when the core electron is ejected from one of the two outer carbon atoms. To explain the spectrum we present a new theoretical approach combining the benefits of a full self-consistent field approach with those of perturbation methods and multi-configurational techniques, thus establishing a powerful tool to reveal molecular orbital symmetry breaking on such an organic molecule, going beyond Lowdins standard definition of electron correlation.
22.	Jain, Sagar M., et al. (författare) Green fabrication of stable lead-free bismuth based perovskite solar cells using a non-toxic solvent 2019 Ingår i: Communications Chemistry. - : NATURE PUBLISHING GROUP. - 2399-3669. ; 2 Tidskriftsartikel (refereegranskat)abstract The very fast evolution in certified efficiency of lead-halide organic-inorganic perovskite solar cells to 24.2%, on par and even surpassing the record for polycrystalline silicon solar cells (22.3%), bears the promise of a new era in photovoltaics and revitalisation of thin film solar cell technologies. However, the presence of toxic lead and particularly toxic solvents during the fabrication process makes large-scale manufacturing of perovskite solar cells challenging due to legislation and environment issues. For lead-free alternatives, non-toxic tin, antimony and bismuth based solar cells still rely on up-scalable fabrication processes that employ toxic solvents. Here we employ non-toxic methyl-acetate solution processed (CH3NH3)(3)Bi2I9 films to fabricate lead-free, bismuth based (CH3NH3)(3)Bi2I9 perovskites on mesoporous TiO2 architecture using a sustainable route. Optoelectronic characterization, X-ray diffraction and electron microscopy show that the route can provide homogeneous and good quality (CH3NH3)(3)Bi2I9 films. Fine-tuning the perovskite/hole transport layer interface by the use of conventional 2,2',7,7'-tetrakis (N,N'-di-p-methoxyphenylamino)-9,9'-spirbiuorene, known as Spiro-OMeTAD, and poly(3-hexylthiophene-2,5-diyl - P3HT as hole transporting materials, yields power conversion efficiencies of 1.12% and 1.62% under 1 sun illumination. Devices prepared using poly(3-hexylthiophene-2,5-diyl hole transport layer shown 300 h of stability under continuous 1 sun illumination, without the use of an ultra violet-filter.
23.	Li, Shuting, et al. (författare) Direct structure determination of vemurafenib polymorphism from compact spherulites using 3D electron diffraction 2023 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 6 Tidskriftsartikel (refereegranskat)abstract The spherulitic morphology is considered to be the most common morphology of crystalline materials and is particularly apparent in melt-crystallized products. Yet, historically, the polycrystalline nature of spherulites has hindered successful crystal structure determination. Here, we report the direct structure determination of a clinical drug, vemurafenib (VMN), in compact spherulite form using 3D electron diffraction (3D ED). VMN has four known polymorphs. We first solved the crystal structures of α-, β-, and γ-VMN from compact spherulites using 3D ED, and the resulting structures were highly consistent with those obtained by single-crystal X-ray diffraction. We then determined the crystal structure of δ-VMN—the least stable polymorph which cannot be cultivated as a single crystal—directly from the compact spherulite sample. We unexpectedly discovered a new polymorph during our studies, denoted as ε-VMN. Single crystals of ε-VMN are extremely thin and not suitable for study by X-ray diffraction. Again, we determined the structure of ε-VMN in a compact spherulite form. This successful structure elucidation of all five VMN polymorphs demonstrates the possibility of directly determining structures from melt-grown compact spherulite samples. Thereby, this discovery will improve the efficiency and broaden the scope of polymorphism research, especially within the field of melt crystallization.
24.	Ma, Le Anh, 1992-, et al. (författare) Understanding charge compensation mechanisms in Na0.56Mg0.04Ni0.19Mn0.70O2 2019 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 2 Tidskriftsartikel (refereegranskat)abstract Sodium-ion batteries have become a potential alternative to Li-ion batteries due to the abundance of sodium resources. Sodium-ion cathode materials have been widely studied with particular focus on layered oxide lithium analogues. Generally, the capacity is limited by the redox processes of transition metals. Recently, however, the redox participation of oxygen gained a lot of research interest. Here the Mg-doped cathode material P2-Na0.56Mg0.04Ni0.19Mn0.70O2 is studied, which is shown to exhibit a good capacity (ca. 120 mAh/g) and high average operating voltage (ca. 3.5 V vs. Na+/Na). Due to the Mg-doping, the material exhibits a reversible phase transition above 4.3 V, which is attractive in terms of lifetime stability. In this study, we combine X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy techniques to shed light on both, cationic and anionic contributions towards charge compensation.
25.	Mahdizadeh, Sayyed Jalil, et al. (författare) Different binding modalities of quercetin to inositol-requiring enzyme 1 of S. cerevisiae and human lead to opposite regulation 2024 Ingår i: Communications Chemistry. - 2399-3669. ; 7:1 Tidskriftsartikel (refereegranskat)abstract The flavonoid Quercetin (Qe) was identified as an activator of Inositol-requiring enzyme 1 (IRE1) in S. cerevisiae (scIre1p), but its impact on human IRE1 (hIRE1) remains controversial due to the absence of a conserved Qe binding site. We have explored the binding modes and effect of Qe on both scIre1p and hIRE1 dimers using in silico and in vitro approaches. The activation site in scIre1p stably accommodates both Qe and its derivative Quercitrin (Qi), thus enhancing the stability of the RNase pocket. However, the corresponding region in hIRE1 does not bind any of the two molecules. Instead, we show that both Qe and Qi block the RNase activity of hIRE1 in vitro, with sub-micromolar IC50 values. Our results provide a rationale for why Qe is an activator in scIre1p but a potent inhibitor in hIRE1. The identification of a new allosteric site in hIRE1 opens a promising window for drug development and UPR modulation.
26.	Moe, Agnes, et al. (författare) Cryo-EM structure and function of S. pombe complex IV with bound respiratory supercomplex factor 2023 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 6:1 Tidskriftsartikel (refereegranskat)abstract Fission yeast Schizosaccharomyces pombe serves as model organism for studying higher eukaryotes. We combined the use of cryo-EM and spectroscopy to investigate the structure and function of affinity purified respiratory complex IV (CIV) from S. pombe. The reaction sequence of the reduced enzyme with O-2 proceeds over a time scale of mu s-ms, similar to that of the mammalian CIV. The cryo-EM structure of CIV revealed eleven subunits as well as a bound hypoxia-induced gene 1 (Hig1) domain of respiratory supercomplex factor 2 (Rcf2). These results suggest that binding of Rcf2 does not require the presence of a CIII-CIV supercomplex, i.e. Rcf2 is a component of CIV. An AlphaFold-Multimer model suggests that the Hig1 domains of both Rcf1 and Rcf2 bind at the same site of CIV suggesting that their binding is mutually exclusive. Furthermore, the differential functional effect of Rcf1 or Rcf2 is presumably caused by interactions of CIV with their different non-Hig1 domain parts. Fission yeast Schizosaccharomyces pombe shares many characteristics with higher eukaryotes. Here, the authors investigate the structure and function of respiratory complex IV from S. pombe, reveal the subunit arrangements and the reaction sequence of O-2 reduction.
27.	Paul, Suman, et al. (författare) 13C- and 15N-labeling of amyloid-β and inhibitory peptides to study their interaction via nanoscale infrared spectroscopy 2023 Ingår i: Communications Chemistry. - 2399-3669. ; 6:1 Tidskriftsartikel (refereegranskat)abstract Interactions between molecules are fundamental in biology. They occur also between amyloidogenic peptides or proteins that are associated with different amyloid diseases, which makes it important to study the mutual influence of two polypeptides on each other's properties in mixed samples. However, addressing this research question with imaging techniques faces the challenge to distinguish different polypeptides without adding artificial probes for detection. Here, we show that nanoscale infrared spectroscopy in combination with C-13, N-15-labeling solves this problem. We studied aggregated amyloid-& beta; peptide (A & beta;) and its interaction with an inhibitory peptide (NCAM1-PrP) using scattering-type scanning near-field optical microscopy. Although having similar secondary structure, labeled and unlabeled peptides could be distinguished by comparing optical phase images taken at wavenumbers characteristic for either the labeled or the unlabeled peptide. NCAM1-PrP seems to be able to associate with or to dissolve existing A & beta; fibrils because pure A & beta; fibrils were not detected after mixing. Interactions of proteins or polypeptides with different secondary structures can be studied in a mixture by nanoscale infrared spectroscopy, however, this technique remains challenging for polypeptides with similar secondary structures. Here, the authors demonstrate clear discrimination of two polypeptides from a mixture by scattering-type scanning near-field optical microscopy when one of the components is labeled with C-13- and N-15-isotopes.
28.	Poronik, Yevgen M., et al. (författare) Deciphering the unusual fluorescence in weakly coupled bis-nitro-pyrrolo[3,2-b]pyrroles 2020 Ingår i: Communications Chemistry. - : NATURE RESEARCH. - 2399-3669. ; 3:1 Tidskriftsartikel (refereegranskat)abstract Electron-deficient pi-conjugated functional dyes lie at the heart of organic optoelectronics. Adding nitro groups to aromatic compounds usually quenches their fluorescence via inter-system crossing (ISC) or internal conversion (IC). While strong electronic coupling of the nitro groups with the dyes ensures the benefits from these electron-withdrawing substituents, it also leads to fluorescence quenching. Here, we demonstrate how such electronic coupling affects the photophysics of acceptor-donor-acceptor fluorescent dyes, with nitrophenyl acceptors and a pyrrolo[3,2-b]pyrrole donor. The position of the nitro groups and the donor-acceptor distance strongly affect the fluorescence properties of the bis-nitrotetraphenylpyrrolopyrroles. Concurrently, increasing solvent polarity quenches the emission that recovers upon solidifying the media. Intramolecular charge transfer (CT) and molecular dynamics, therefore, govern the fluorescence of these nitro-aromatics. While balanced donor-acceptor coupling ensures fast radiative deactivation and slow ISC essential for large fluorescence quantum yields, vibronic borrowing accounts for medium dependent IC via back CT. These mechanistic paradigms set important design principles for molecular photonics and electronics. Owing to their electron-withdrawing nature, nitro-groups are desirable in the design of electron-deficient light-sensitizing aromatic pi-conjugated molecules, but most nitro-aromatics are not fluorescent. Here, the authors show how balanced donor-acceptor coupling ensures fast radiative deactivation and slow intersystem crossing in bis-nitrotetraphenylpyrrolopyrroles.
29.	Rohr, Jason A., et al. (författare) The role of adsorbates in the green emission and conductivity of zinc oxide 2019 Ingår i: Communications Chemistry. - : NATURE PUBLISHING GROUP. - 2399-3669. ; 2 Tidskriftsartikel (refereegranskat)abstract Zinc oxide is a versatile semiconductor with an expansive range of applications including lighting, sensing and solar energy conversion. Two central phenomena coupled to its performance that remain heavily investigated are the origin of its sub-band-gap green emission and the nature of its conductivity. We report photoluminescence and dark conductivity measurements of zinc oxide nanoparticle films under various atmospheric conditions that demonstrate the vital role of adsorbates. We show that the UV emission and conductivity can be tuned reversibly by facilitating the adsorption of species that either donate or extract electrons from the conduction band. When the conductivity data are compared with photoluminescence spectra taken under the same ambient conditions, the green emission can be directly linked to surface superoxide formation, rather than surface hydroxylation or native defects such as oxygen vacancies. This demonstrates how and explains why the green emission can be controlled by surface reactivity and chemical environment.
30.	Seibel, Elena, et al. (författare) Genome mining for macrolactam-encoding gene clusters allowed for the network-guided isolation of β-amino acid-containing cyclic derivatives and heterologous production of ciromicin A 2023 Ingår i: Communications Chemistry. - 2399-3669. ; 6:1 Tidskriftsartikel (refereegranskat)abstract β-Amino acid-containing macrolactams represent a structurally diverse group of bioactive natural products derived from polyketides; however we are currently lacking a comprehensive overview about their abundance across bacterial families and the underlying biosynthetic diversity. In this study, we employed a targeted β-amino acid-specific homology-based multi-query search to identify potential bacterial macrolactam producers. Here we demonstrate that approximately 10% of each of the identified actinobacterial genera harbor a biosynthetic gene cluster (BGC) encoding macrolactam production. Based on our comparative study, we propose that mutations occurring in specific regions of polyketide synthases (PKS) are the primary drivers behind the variation in macrolactam ring sizes. We successfully validated two producers of ciromicin A from the genus Amycolatopsis, revised the composition of the biosynthetic gene cluster region mte of macrotermycins, and confirmed the ciromicin biosynthetic pathway through heterologous expression. Additionally, network-based metabolomic analysis uncovered three previously unreported macrotermycin congeners from Amycolatopsis sp. M39. The combination of targeted mining and network-based analysis serves as a powerful tool for identifying macrolactam producers and our studies will catalyze the future discovery of yet unreported macrolactams.
31.	Staats, Roxine, et al. (författare) Screening of small molecules using the inhibition of oligomer formation in α-synuclein aggregation as a selection parameter 2020 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 3:1 Tidskriftsartikel (refereegranskat)abstract The aggregation of α-synuclein is a central event in Parkinsons’s disease and related synucleinopathies. Since pharmacologically targeting this process, however, has not yet resulted in approved disease-modifying treatments, there is an unmet need of developing novel methods of drug discovery. In this context, the use of chemical kinetics has recently enabled accurate quantifications of the microscopic steps leading to the proliferation of protein misfolded oligomers. As these species are highly neurotoxic, effective therapeutic strategies may be aimed at reducing their numbers. Here, we exploit this quantitative approach to develop a screening strategy that uses the reactive flux toward α-synuclein oligomers as a selection parameter. Using this approach, we evaluate the efficacy of a library of flavone derivatives, identifying apigenin as a compound that simultaneously delays and reduces the formation of α-synuclein oligomers. These results demonstrate a compound selection strategy based on the inhibition of the formation of α-synuclein oligomers, which may be key in identifying small molecules in drug discovery pipelines for diseases associated with α-synuclein aggregation.
32.	Tajnšek, Tia K., et al. (författare) Design and degradation of permanently porous vitamin C and zinc-based metal-organic framework 2022 Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5:1 Tidskriftsartikel (refereegranskat)abstract Bioapplication is an emerging field of metal-organic frameworks (MOF) utilization, but biocompatible MOFs with permanent porosity are still a rarity in the field. In addition, biocompatibility of MOF constituents is often overlooked when designing bioMOF systems, intended for drug delivery. Herein, we present the a Zn(II) bioMOF based on vitamin C as an independent ligand (bioNICS-1) forming a three-dimensional chiral framework with permanent microporosity. Comprehensive study of structure stability in biorelavant media in static and dynamic conditions demonstrates relatively high structure resistivity, retaining a high degree of its parent specific surface area. Robustness of the 3D framework enables a slow degradation process, resulting in controllable release of bioactive components, as confirmed by kinetic studies. BioNICS-1 can thus be considered as a suitable candidate for the design of a small drug molecule delivery system, which was demonstrated by successful loading and release of urea—a model drug for topical application—within and from the MOF pores.
33.	Walz, Marie-Madeleine, et al. (författare) Microscopic origins of conductivity in molten salts unraveled by computer simulations 2021 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 4 Tidskriftsartikel (refereegranskat)abstract Molten salts are crucial materials in energy applications, such as batteries, thermal energy storage systems or concentrated solar power plants. Still, the determination and interpretation of basic physico-chemical properties like ionic conductivity, mobilities and transference numbers cause debate. Here, we explore a method for determination of ionic electrical mobilities based on non-equilibrium computer simulations. Partial conductivities are then determined as a function of system composition and temperature from simulations of molten LiF alpha Cl beta I gamma (with alpha + beta + gamma = 1). High conductivity does not necessarily coincide with high Li+ mobility for molten LiF alpha Cl beta I gamma systems at a given temperature. In salt mixtures, the lighter anions on average drift along with Li+ towards the negative electrode when applying an electric field and only the heavier anions move towards the positive electrode. In conclusion, the microscopic origin of conductivity in molten salts is unraveled here based on accurate ionic electrical mobilities and an analysis of the local structure and kinetics of the materials. Molten salt electrolytes are widely used in energy storage and conversion, but our understanding of conductivity trends remains incomplete. Here, computational approaches are used to determine ionic electrical mobilities, local structures, and kinetics, unravelling the origins of conductivity in molten lithium halide salts.
34.	Wang, HZ, et al. (författare) Multivariate effects of pH, salt, and Zn2+ ions on Aβ40 fibrillation 2022 Ingår i: Communications chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 5:1, s. 171- Tidskriftsartikel (refereegranskat)abstract Amyloid-β (Aβ) peptide aggregation plays a central role in the progress of Alzheimer’s disease (AD), of which Aβ-deposited extracellular amyloid plaques are a major hallmark. The brain micro-environmental variation in AD patients, like local acidification, increased ionic strength, or changed metal ion levels, cooperatively modulates the aggregation of the Aβ peptides. Here, we investigate the multivariate effects of varied pH, ionic strength and Zn2+ on Aβ40 fibrillation kinetics. Our results reveal that Aβ fibrillation kinetics are strongly affected by pH and ionic strength suggesting the importance of electrostatic interactions in regulating Aβ40 fibrillation. More interestingly, the presence of Zn2+ ions can further alter or even reserve the role of pH and ionic strength on the amyloid fibril kinetics, suggesting the importance of amino acids like Histidine that can interact with Zn2+ ions. Both pH and ionic strength regulate the secondary nucleation processes, however regardless of pH and Zn2+ ions, ionic strength can also modulate the morphology of Aβ40 aggregates. These multivariate effects in bulk solution provide insights into the correlation of pH-, ionic strength- or Zn2+ ions changes with amyloid deposits in AD brain and will deepen our understanding of the molecular pathology in the local brain microenvironment.
35.	Wang, Shule, et al. (författare) Van Krevelen diagrams based on machine learning visualize feedstock-product relationships in thermal conversion processes 2023 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 6:1 Tidskriftsartikel (refereegranskat)abstract Feedstock properties play a crucial role in thermal conversion processes, where understanding the influence of these properties on treatment performance is essential for optimizing both feedstock selection and the overall process. In this study, a series of van Krevelen diagrams were generated to illustrate the impact of H/C and O/C ratios of feedstock on the products obtained from six commonly used thermal conversion techniques: torrefaction, hydrothermal carbonization, hydrothermal liquefaction, hydrothermal gasification, pyrolysis, and gasification. Machine learning methods were employed, utilizing data, methods, and results from corresponding studies in this field. Furthermore, the reliability of the constructed van Krevelen diagrams was analyzed to assess their dependability. The van Krevelen diagrams developed in this work systematically provide visual representations of the relationships between feedstock and products in thermal conversion processes, thereby aiding in optimizing the selection of feedstock and the choice of thermal conversion technique.
36.	Yin, Yuqing, et al. (författare) Synthesis of rare-earth metal compounds through enhanced reactivity of alkali halides at high pressures 2022 Ingår i: Communications Chemistry. - : Nature Portfolio. - 2399-3669. ; 5:1 Tidskriftsartikel (refereegranskat)abstract Chemical stability of the alkali halides NaCI and KCI has allowed for their use as inert media in high-pressure high-temperature experiments. Here we demonstrate the unexpected reactivity of the halides with metals (Y, Dy, and Re) and iron oxide (FeO) in a laser-heated diamond anvil cell, thus providing a synthetic route for halogen-containing binary and ternary compounds. So far unknown chlorides, Y2Cl and DyCl, and chloride carbides, Y2ClC and Dy2ClC, were synthesized at -40 GPa and 2000 K and their structures were solved and refined using in situ single-crystal synchrotron X-ray diffraction. Also, FeCl2 with the HP-PdF2-type structure, previously reported at 108 GPa, was synthesized at similar to 160 GPa and 2100 K. The results of our ab initio calculations fully support experimental findings and reveal the electronic structure and chemical bonding in these compounds.
37.	Zand, Zahra, et al. (författare) Role of decomposition products in the oxidation of cyclohexene using a manganese(III) complex 2023 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 6:1 Tidskriftsartikel (refereegranskat)abstract Metal complexes are extensively explored as catalysts for oxidation reactions; molecular-based mechanisms are usually proposed for such reactions. However, the roles of the decomposition products of these materials in the catalytic process have yet to be considered for these reactions. Herein, the cyclohexene oxidation in the presence of manganese(III) 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine chloride tetrakis(methochloride) (1) in a heterogeneous system via loading the complex on an SBA-15 substrate is performed as a study case. A molecular-based mechanism is usually suggested for such a metal complex. Herein, 1 was selected and investigated under the oxidation reaction by iodosylbenzene or (diacetoxyiodo)benzene (PhI(OAc)(2)). In addition to 1, at least one of the decomposition products of 1 formed during the oxidation reaction could be considered a candidate to catalyze the reaction. First-principles calculations show that Mn dissolution is energetically feasible in the presence of iodosylbenzene and trace amounts of water. Metal complexes are often used as catalysts for oxidation reactions, however, there are open questions about the role of the decomposition products in the catalytic process. Here, the authors explore the potential role of decomposition products in the oxidation of cyclohexene using a manganese(III) complex catalyst adsorbed on an SBA-15 substrate.
38.	Zhou, Chao, et al. (författare) Highly congested spiro-compounds via photoredox-mediated dearomative annulation cascade 2022 Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 5:1 Tidskriftsartikel (refereegranskat)abstract Photo-mediated radical dearomatization involving 5-exo-trig cyclizations has proven to be an important route to accessing spirocyclic compounds, whereas 6-exo-trig spirocyclization has been much less explored. In this work, a dearomative annulation cascade is realized through photoredox-mediated C-O bond activation of aromatic carboxylic acids to produce two kinds of spirocyclic frameworks. Mechanistically, the acyl radical is formed through oxidation of triphenylphosphine and subsequent C-O bond cleavage, followed by a 6-exo-trig cyclization/SET/protonation sequence to generate the spiro-chromanone products in an intramolecular manner. Furthermore, the protocol was extended to more challenging intermolecular tandem sequences consisting of C-O bond cleavage, radical addition to an alkene substrate, and 5-exo-trig cyclization to yield complex spirocyclic lactams. Photo-mediated radical dearomatization involving 5-exo-trig cyclizations has proven to be an important route to accessing spirocyclic compounds, whereas 6-exo-trig spirocyclization has been much less explored. Here, a dearomative annulation cascade is realized through a photoredox-mediated C-O bond activation of aromatic carboxylic acids to produce two kinds of spirocyclic frameworks, whereby the spirocyclizations are triggered by acyl radical formation from benzoic acids leading to spiro-chromanones via a direct intramolecular 6-exo-trig cyclization or spirocyclic lactams via an intermolecular addition/5-exo-trig cyclization cascade.
39.	Zhou, Guojun, 1990-, et al. (författare) Structure determination of a low-crystallinity covalent organic framework by three-dimensional electron diffraction 2023 Ingår i: Communications Chemistry. - 2399-3669. ; 6 Tidskriftsartikel (refereegranskat)abstract Covalent organic frameworks (COFs) have been attracting intense research due to their permanent porosity, designable architecture, and high stability. However, COFs are challenging to crystallize and their synthesis often results in tiny crystal sizes and low crystallinities, which hinders an unambiguous structure determination. Herein, we demonstrate that the structure of low-crystallinity COF Py-1P nanocrystals can be solved by coupling three-dimensional electron diffraction (3DED) with simulated annealing (SA). The resulting model is comparable to that obtained from high-crystallinity samples by dual-space method. Moreover, for low-resolution 3DED data, the model obtained by SA shows a better framework than those provided by classic direct method, dual-space method, and charge flipping. We further simulate data with different resolutions to understand the reliability of SA under different crystal quality conditions. The successful determination of Py-1P structure by SA compared to other methods provides new knowledge for using 3DED to analyze low-crystallinity and nanosized materials.

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