ChemRxiv
Not a member yet
27047 research outputs found
Sort by
Stable Antiaromatic [16]Triphyrin(2.1.1) with Core-Modification: Synthesis via a 16π Electrocyclic Reaction
No full textAntiaromatic porphyrinoids have attracted significant attention owing to their unique electronic properties and potential applications. However, synthesis of antiaromatic contracted porphyrinoids is challenging owing to the inherent instability associated with smaller ring sizes. In this study, we report the synthesis and characterization of the first stable trioxa[16]triphyrin(2.1.1), a novel 16π antiaromatic contracted porphyrinoid. We utilized a core modification approach to stabilize the [16]triphyrin(2.1.1). X-ray crystallographic analysis revealed a nearly planar structure. Electrochemical studies demonstrated reversible oxidation behavior and a small HOMO–LUMO gap, which was consistent with its antiaromatic nature. Chemical oxidation yielded an aromatic [14]triphyrin(2.1.1) dication, highlighting the antiaromaticity–aromaticity switching capability of this system. This synthesis involved the discovery of a key intermediate, dihydrotrioxatriphyrin(2.1.1), which underwent oxidative dehydrogenation to yield the target compound. Theoretical calculations suggested that dihydrotrioxatriphyrin(2.1.1) formed via a rare 16π electrocyclic reaction. The successful synthesis and characterization of this stable trioxa[16]triphyrin(2.1.1) underscores the potential of the core modification strategies for the rational design of novel antiaromatic systems with tunable properties. Moreover, the discovery of the rare 16π electrocyclic reaction advances the understanding of high-order pericyclic processes and may inspire new synthetic strategies for complex macrocyclic compounds
Bottom-up Precision Engineering of Porous Medium for High-Performance Chromatography Based on Stereolithography 3D Printing
No full textEngineering of high-performance chromatography medium, has long been esteemed as an art rather than science, this raised a great challenge in securing separation consistency, method transferability and scaling-up in purification of biomolecules. Herein, we report a bottom-up engineering strategy for chromatography media utilizing 3D-printing technology. Combining micrometer stereolithography and nanometer pore chemistry, the strategy enables precision engineering of high-performance separation media in diverse scales, shapes and chemistry. Between 1,000 devices, exceptional performance consistency was demonstrated by superb column-to-column and batch-to-batch reproducibility (retention time CV 2.04%). Ultra-fast separations of intact proteins and antibodies were realized in reversed-phase and hydrophobic interaction chromatography: within 1 minute, resolution > 1.5 was achieved. Purification of native proteins was directly amplified three orders of magnitude: 12 mg hemeproteins were isolated in 8 min at negligible scaling-up cost, supporting liter-scale processing within 7 h on one 20 mm i.d. column. With unprecedented advantages in fully automatic and parallel production capacity, high-fidelity microstructure and chemistry across dimensions, and highly efficient method transfer and scaling-up, the stereolithography engineered chromatography media may open a green and sustainable path to speeding up separation and purification processes from primary analysis to mass-production of biomolecular entities, as demanded in biosynthesis and pharmaceutical industries
A photochemical strategy towards Michael addition reactions of cyclopropenes
No full textThe development of Michael addition reactions to conjugated cyclopropenes is a challenge in synthesis due to the fleeting and reactive nature of such strained Michael acceptor systems. Herein, the development of a photochemical approach towards such conjugated cyclopropenes is reported that serves as a strategic entry point to densely functionalized cyclopropanes in a diastereoselective fashion. The process involves the light-mediated generation of transient cyclopropenyl α,β-unsaturated esters from vinyl diazo esters, followed by an organic base catalyzed nucleophilic addition of N-heterocycles to directly access β-N-heterocyclic cyclopropanoic esters. With this synergistic approach, various trisubstituted cyclopropanes bearing N-heteroaryl and N-heterocyclic rings such as indole, pyrrole, benzimidazole, isatin, pyridinone and quinolinone were accessed efficiently in good yield and decent to good diastereoselectivities. Further, β-indolyl cyclopropanoic acids have been synthesized and were successfully evaluated as FABP-4 inhibitors. Theoretical calculations have been performed to elucidate the mechanism which was further supported by experimental findings
Characterization and Optimization of Vesicle Properties in bioPISA: From Size Distribution to Post-Assembly Loading
No full textThis study investigates the formation and properties of vesicles produced via biocatalytic Polymerization-Induced Self-Assembly (bioPISA) as artificial cells. We explore methods for achieving size uniformity, including gentle centrifugation and sucrose gradient centrifugation, and examined the effects of stirring speed on vesicle morphology. The internal structure of the vesicles, characterized by a polymer-rich matrix, is analysed using fluorescence correlation spectroscopy (FCS). Additionally, we demonstrate the feasibility of loading macromolecules into pre-formed vesicles using electroporation, successfully incorporating a fluorescent protein. Our findings provide a foundation for further developing polymeric vesicles, with controlled morphologies for various applications in synthetic biology
From Generation to Collection – Impact of Deposition Temperature on Charge Carrier Dynamics of High-Performance Vacuum-Processed Organic Solar Cells
No full textVacuum-processed organic solar cells (VP-OSCs) possess many advantages for scalability. However, as the academic community focusses on high performing solution-processed OSCs, detailed studies about the relation between morphology and device characteristics in VP-OSCs are rare. Here, we present a study on a model donor/fullerene VP-OSC system deposited at different substrate temperatures. Substrate heating results in increases in current density and fill factor (FF). The changes in morphology are characterised by grazing-incidence wide-angle scattering (GIWAXS) and resonant soft X-ray scattering (RSoXS). The increase in the degree of crystallinity and preferential orientation of the donor molecule in heated samples results in enhanced absorption increasing current density. The exciton and charge separation efficiency studied by transient absorption and photoluminescence quenching show only minor differences. To study the FF differences, charge transport and non-geminate recombination are studied by optoelectronic measurements and device simulations. The charge carrier kinetics are governed by a large density of trap states. While the energetic disorder and non-geminate recombination under open circuit conditions remain largely unchanged, the increased effective mobility and lower transport disorder observed in photocurrent transients explain the increased collection efficiency for heated devices. We relate this to the increased donor phase purity. Our results suggest that charge recombination and transport are governed by different aspects of disorder related to amorphous and crystalline donor phases. Quantitative comparison with high FF solution-processed OSCs reveals that the low mobility limits FF. Finally, drift-diffusion simulations give an outlook for possible performance increases through further optimisation of the deposition control
Navigating Solvent Chemistry and Microstructures: Towards Mechanically-enhanced Ceramic-rich Composite Electrolytes
No full textUltra-thin ceramic-rich solid composite electrolytes provide a safer and potentially higher energy-density alternative to liquid electrolytes used in today’s lithium-ion batteries. Producing ultra-thin composites with ceramic-like ionic conductivity requires the incorporation of a polymeric binder for enhanced ductility. In this perspective, we discuss two key aspects that must be considered when designing composite electrolytes: (1) the mechanical properties of the composite and its correlation with the ceramic and polymer microstructure, and (2) the chemistry between the ceramic electrolytes, polymers, and solvents used to process the composites. We highlight the importance of understanding (1) the ceramic structure, crystallinity, and particle size upon solvent processing and (2) the ceramic/polymer interface chemistry and its correlation with the microstructure of the composites. We present opportunities in fabricating ultra-thin support structures for composites, optimizing ceramic particle packing parameters, and routes toward mechanically enhanced, compact, composite-based solid-electrolytes
From High Dimensions to Human Comprehension: Exploring Dimensionality Reduction for Chemical Space Visualization
No full textDimensionality reduction is an important exploratory data analysis method that allows high-dimensional data to be represented in a human-interpretable lower-dimensional space. It is extensively applied in the analysis of chemical libraries, where chemical structure data — represented as high-dimensional feature vectors—are transformed into 2D or 3D chemical space maps. In this paper, commonly used dimensionality reduction techniques — Principal Component Analysis (PCA), t-Distributed Stochastic Neighbor Embedding (t-SNE), Uniform Manifold Approximation and Projection (UMAP), and Generative Topographic Mapping (GTM) — are evaluated for exploration of subsets of small molecule organic compounds from ChEMBL database. The performance of these methods is examined in terms of neighborhood preservation and visualization capabilities, and the strengths and limitations are discussed
Regioselectivity of non-Symmetrical Borylated Dienes via EnT Ca-talysis: Unveiling the Relationship between Structure and Reactivity
No full textEnergy transfer catalysis (EnT) has had a profound impact on contemporary organic synthesis enabling the construction of higher in energy, complex molecules, via efficient access to the triplet excited state. Despite this, intermolecular reactivity, and the unique possibility to access several reaction pathways via a central triplet diradical has rendered control over reaction outcomes, an intractable challenge. Extended chromophores such as non-symmetrical dienes have the potential to undergo 2+2 cycloaddition, 4+2 cycloaddition or geometric isomerization, which, in combination with other mechanistic considerations (site- and regioselectivity), results in chemical reactions that are challenging to regulate. Leveraging spin density as a predictive tool, in combination with the use of a core functionality that can be adequately tuned to potentially modulate reactivity, would be highly enabling in revealing the intimate links between core structure and EnT induced reactivity. Herein, we utilize boron as a tool to explore reactivity of non-symmetrical dienes under EnT catalysis, paying particular attention to the impact of boron hybridization effects on the target reactivity. Through this, a highly site- and regioselective 2+2 cycloaddition was realized with the employed boron motif effecting reaction efficiency. Reaction divergence to enable 4+2 cycloaddition was achieved, while a counterintuitive regiodivergence was observed in geometric isomerization versus 2+2 cycloaddition. The observed reactivity was validated via an in-depth mechanistic investigation determining the origin of reactivity and regiodivergence in competing EnT processes and revealing the intimate links between structure and reactivity
A Chiral Nanohoop as Highly Efficient Asymmetric Organocatalyst
No full textChiral phosphoric acids are privileged organocatalysts that have been shown to facilitate a large variety of asymmetric transformations. In recent years, the BINOL scaffold has been equipped with large aromatic groups and transformed into dimeric imidodiphosphates to im-prove both chiral induction and catalyst turnover by tuning pKa and creating a confined space around the catalytic center. In this work, we report an alternative approach for achieving such a confinement effect within the cavity of a chiral, shape-persistent “carbon nanohoop” mac-rocycle. We integrated a BINOL-derived phosphoric acid into the [9]cycloparaphenylene (CPP) scaffold and employed the nanohoop as organocatalyst for the asymmetric transfer hydrogenation of quinolines. We found that the chiral macrocycle shows excellent catalytic activity with near-quantitative yields and enantioselectivities up to 96% ee, which is far supe-rior to comparable non-cyclic reference catalysts. While the scope for quinolines bearing aromatic substituents is wide, we made the counterintuitive observation that the macrocyclic catalyst is not active for smaller alkyl-substituted substrates, which indicates that highly spe-cific non-covalent effects determine the reaction outcome within the nanohoop cavity. These results suggest that outstanding selectivities can be achieved by endowing organocatalysts not only with supramolecular binding sites but also with unusual topologies
Characterizing Indoor-Outdoor PM2.5 Concentrations Using Low-Cost Sensor Measurements in Residential Homes in Dhaka, Bangladesh
No full textWe collected paired measurements of indoor and outdoor PM2.5 concentrations at 17 homes in Dhaka, Bangladesh, to quantify indoor-outdoor levels, their spatio-temporal variations, and influencing factors. A pair of PurpleAir PM2.5 sensors were deployed at each home, one indoors and the other outdoors, during the wet (June to August 2021) and dry (December 2021 to February 2022) seasons, and the locally calibrated (against a beta attenuation monitor) and quality-assured data were used for analysis. Indoor and outdoor PM2.5 levels were three times higher during the dry season (indoor 146 ± 22 µg/m³, outdoor 153 ± 23 µg/m³) than during the wet season (indoor 52 ± 12 µg/m³, outdoor 50 ± 11 µg/m³). Indoor to outdoor (I/O) ratios were close to 1 in both seasons (dry: 0.97 ± 0.14, wet: 1.05 ± 0.19). This suggests that regional background pollution levels significantly influence indoor levels observed in different households. Higher infiltration factors (dry: 0.83 ± 0.12; wet: 0.87 ± 0.14), determined through mixed effect regression of parallel indoor and outdoor timeseries data, further highlight the substantial impact of outdoor pollution on indoor levels. Data from individual households exhibited strong temporal correlation between indoor and outdoor levels in both seasons (Pearson R: 0.82 ± 0.12 during the dry season and 0.83 ± 0.14 during the wet season), whereas indoor-outdoor spatial correlations across measured households were moderate (R: 0.49 and 0.62 during dry and wet seasons, respectively). These spatial correlations and empirical regression modeling suggest that while the spatial variation of outdoor PM2.5 levels significantly influences indoor levels\u27 spatial variation, other factors such as indoor source activities and ventilation-related features play crucial roles in explaining variabilities in indoor PM2.5 across homes. Overall, our study suggests that indoor environments in Dhaka city are nearly as polluted as outdoor settings, and this locally derived scientific evidence can be valuable for enhancing public awareness and developing mitigation measures to reduce PM2.5 exposures in Bangladesh