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Ion-Radical Mediated Multi-Color Ultra-Long Afterglow Materials
No full textPure organic persistent room temperature phosphorescence (RTP) has shown great potential in numerous applications, ranging from information encryption and display technologies to bio-applications and beyond. In this work, a suite of multi-color long-lived RTP materials featuring distinct afterglow emissions was constructed using an ion-radical mediated approach. b[c]p/MeBPO emitted a vivid yellow afterglow centered at 560 nm with an impressively long lifetime of 860.01 ms. While compound b[a]a exhibited a near-infrared (NIR) afterglow (τ = 215.96 ms) after doping into the matrix. The transient absorption spectroscopy investigations disclosed that the observed afterglow phenomenon was fundamentally tied to the generation of radical ions rather than the exciplex. These radical ions resulted from the reduction quenching process of the triplet excited state of compound BPO by the ground state of the doping agent. A novel evaluation methodology was devised, rooted in Marcus theory, to gauge the potential of a specific dopant-matrix combination towards generating pronounced afterglow. According to this framework, the enhancement of the afterglow is directly proportional to the decrease in the activation energy (ΔG≠) associated with the electron transfer reaction occurring between the dopant and the matrix. Notably, when the ΔG≠ surpasses 30 kcal/mol, no observable afterglow occurs, as higher ΔG≠ values significantly impede the electron transfer reaction between the two components. Furthermore, the system exhibits exceptional sensitivity, with the dopant as low as 0.02‰ molar ratio between the dopant and the host material. This remarkable dependence of afterglow intensity on the dopant concentration renders the bi-component RTP system highly promising for applications requiring ultra-high sensitivity and broad-spectrum detection capabilities
Co(III)-Catalyzed Coupling of Enaminones with Oxadiazolones for Imidazole Synthesis
No full textSkeleton speciation-oriented synthesis as the conventional wisdom of synthetic methodology development prioritizes skeleton as the center of attention for organic speciation, the creation of organic species with differentiated structure-defining feature. The passive as-is assembly of appendages as a secondary accessory inevitably leads to the convergence of appendage pattern on skeleton. We report herein a synthetic practice of appendage speciation-oriented synthesis, emphasizing appendages as the focal point for organic speciation. This synthetic modality seeks, proactively, the maximization of type-, position-, and configuration-variance of appendages through both in situ and ex situ appendage speciation. A Co(III) catalytic protocol in accord with this synthetic modality has been established for coupling of enaminones and oxadiazolones to imidazoles, allowing the achievement of full position-variance of appendages. This translates to expanded reaction and structural development scope and can provide a fertile ground for productive organic synthesis
Cobalt(I) Pincer Complexes as Catalysts for CO2 Hydrogenation to Formate
No full textCarbon dioxide hydrogenation with base to generate formate salts can provide a means of storing hydrogen in an energy dense solid. The stored hydrogen can later be released upon acidification of the formate salts or formic acid can be used directly in fuel cells. However, this application requires catalytic CO2 hydrogenation, which would ideally use an earth abundant metal as the catalyst. In this article, six new (CNC)CoIL2 pincer complexes were synthesized and fully characterized, including single crystal X-Ray diffraction analysis on four new complexes. These complexes contain an imidazole-based (1R) N-heterocyclic carbene (NHC) ring or a benzimidazole based NHC ring (2R) in the CNC pincer. The R group is para to N on the pyridine ring and been varied from electron withdrawing (CF3) to donating (Me, OMe) substituents. The L type ligands have included CO and phosphine ligands (in PPh32 and PMe32). Thus, two known Co complexes (1, 1OMe) and six new complexes (1Me, 1CF3, 2, 2OMe, PPh32, PMe32) were studied for the CO2 hydrogenation reaction. In general, the unsubstituted CNC pincer complexes bearing two carbonyl ligands led to the highest activity. The best catalyst, 2, remains active for over 16 h and produces a turnover number of 39,800 with 20 bars of 1:1 CO2 / H2 mixture at 60 °C
Synergistic Photoenzymatic Catalysis Enables Synthesis of a-Tertiary Amino Acids Using Threonine Aldolases
No full texta-Tertiary amino acids are essential components of drugs and agrochemicals, yet traditional syntheses are step-intensive and provide access to a limited range of structures with vary-ing levels of enantioselectivity. Here, we report the α-alkylation of unprotected alanine and glycine by pyridinium salts using pyridoxal (PLP)-dependent threonine aldolases with a Rose Bengal photoredox catalyst. The strategy efficient-ly prepares various a-tertiary amino acids in a single chemical step as a single enantiomer. UV-vis spectroscopy studies re-veal a ternary interaction between the pyridinium salt, pro-tein, and photocatalyst, which we hypothesize is responsible for localizing radical formation to the protein active site. This method highlights the opportunity for combining photoredox catalysts with enzymes to reveal new catalytic functions for known enzymes
Bipolar membrane capacitive deionization for the selective capture of lithium ions from brines and conversion to lithium hydroxide
No full textMeeting the increasing demand for lithium in vehicle electrification and renewable energy storage requires innovations in lithium-ion (Li+) separations. Traditional solar evaporation methods for lithium recovery are slow and consume tremendous volumes of water and secondary chemicals (acids and bases). This study introduces a bipolar membrane capacitive deionization (BPM-CDI) unit for direct lithium extraction (DLE) and LiOH production without the external addition of acids and bases. Utilizing de-lithiated lithium-iron-phosphate (LFP) coated carbon cloth electrodes, the BPM-CDI unit demonstrates selective Li+ capture over competing ions. Molecular dynamics (MD) simulations and H-cell experiments elucidate pH inversion mechanisms during Li+ release, yielding LiOH. The BPM-CDI platform efficiently removes Li+ from synthetic brines featuring 8x higher Mg2+ concentrations (200 ppm Mg2+) and 26x higher Na+ concentrations (682 ppm Na+), achieving a LiOH concentration of 36 ppm after 8 cycles of recirculation. Post-mortem analysis confirms electrode integrity and stability. BPM-CDI integrated with selective electrodes is a promising electrochemical separation-reactor platform for lithium recovery while producing LiOH
Structure-guided discovery of orexin receptor-binding PET ligands
No full textMolecular imaging using positron emission tomography (PET) can serve as a promising tool for visualizing biological targets in the brain. Insights into the expression pattern and the in vivo imaging of the G protein-coupled orexin receptors OX1R and OX2R will further our understanding of the orexin system and its role in various physiological and pathophysiological processes. Guided by crystal structures of our lead compound JH112 and the approved hypnotic drug suvorexant bound to OX1R and OX2R, respectively, we herein describe the design and synthesis of two novel radioligands, [18F]KD23 and [18F]KD10. Key to the success of our structural modifications was a bioisosteric replacement of the triazole moiety with a fluorophenyl group. The 19F-substituted analog KD23 showed high affinity for the OX1R and selectivity over OX2R, while the high affinity ligand KD10 displayed similar Ki values for both subtypes. Radiolabeling starting from the respective pinacol ester precursors resulted in excellent radiochemical yields of 93% and 88% for [18F]KD23 and [18F]KD10, respectively, within 20 minutes. The new compounds will be useful in PET studies aimed at subtype-selective imaging of orexin receptors in brain tissue
Distribution of Single-Particle Resonances Determines Plasmonic Response of Disordered Nanoparticle Ensembles
No full textUnderstanding how colloidal soft materials interact with light is crucial to rational design of optical metamaterials. Electromagnetic simulations are computationally expensive and have primarily been limited to model systems described by a small number of particles -- dimers, small clusters, and small periodic unit cells of superlattices. In this work, we study the optical properties of bulk, disordered materials comprising a large number of plasmonic colloidal nanoparticles using Brownian dynamics simulations and the mutual polarization method. We investigate the far-field and near-field optical properties of both colloidal fluids and gels, which require thousands of nanoparticles to describe statistically. We show that these disordered materials exhibit a distribution of particle-level plasmonic resonance frequencies that determines their ensemble optical response. Nanoparticles with similar resonant frequencies form anisotropic and oriented clusters embedded within the otherwise isotropic and disordered microstructures. These collectively resonating morphologies can be tuned with the frequency and polarization of incident light. Knowledge of particle resonant distributions may help to interpret and compare the optical responses of different colloidal structures, correlate and predict optical properties, and rationally design soft materials for applications harnessing light
Computational Analysis of Fully Activated Orexin Receptor 2 Across Various Thermodynamic Ensembles with Surface Tension Monitoring
No full textMolecular dynamics (MD) simulations play a crucial role in understanding dynamic biological processes at nanoscale, yet predicting non-equilibrium phenomena like receptor activation presents significant challenges. In such cases, the primary objective isn\u27t merely achieving stable MD trajectories; rather, it\u27s imperative to remove all artificial restraints in order to unveil suppressed mechanical modes within the simulated systems, and thus advancing computer-aided drug design. In this study, we investigated the stability of the fully activated conformation of the orexin receptor 2 (OX2R) embedded in a pure 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) bilayer using MD simulations. Various thermodynamic ensembles (i.e. NPT, NVT, NVE, NPAT, µVT and NPγT) were employed to explore the system\u27s dynamics comprehensively. 11 physical quantities, including so called OX2R activation distance, essential protein dynamics, membrane thickness, hydrogen order parameters, and ligand-protein potential energies, across 104 MD trajectories covering 10.4 µs of chemical time were calculated and profoundly analyzed. Special attention was given to assessing surface tension within the simulation box, particularly under NPγT conditions, where 21 nominal surface tension constants were evaluated. Notably, our findings suggest that traditional thermodynamic ensembles like NPT may not adequately control physical properties of the POPC membrane, impacting the plausibility of the OX2R model. In general, the performed study underscores the importance of employing the NPγT ensemble for computational investigations of membrane-embedded receptors, as it effectively maintains zero surface tension in the simulated system. These results offer valuable insights for future research aimed at understanding receptor dynamics and designing targeted therapeutics
Demonstrating surface and plasma chemistry with a non-thermal atmospheric plasma
No full textA low-cost plasma nozzle/setup was developed to allow demonstrations and hands-on experimentation with non-thermal plasmas of air and other gases. Several high-tech plasma applications, such as surface cleaning and activation, as well as mild, but effective sterilization will be explained and adapted to be eagerly explored by undergraduate and senior high school students. The results were surprisingly similar to those obtained with a commercial plasma treatment system. While the focus is on the experimental introduction to plasma physics and chemistry, it will be highlighted how a multidisciplinary approach enables the study and discussion of important concepts ranging from surface energies and contact angles to environmental or microbiological control
Neural network potentials for exploring condensed phase chemical reactivity
No full textRecent advances in machine learning o er powerful tools for exploring complex reaction mechanisms in condensed phases via reactive simulations. In this tutorial review, we describe the key challenges associated with simulating reactions in condensed phases, we introduce neural network potentials and detail how they can be trained. We emphasize the importance of active learning to construct the training set, and show how these reactive force elds can be integrated with enhanced sampling techniques, including transition path sampling. We illustrate the capabilities of these new methods with a selection of applications to chemical reaction mechanisms in solution and at interfaces