Analytical Chemistry
DOI: 10.1021/acs.analchem.3c05204
Photocatalytic Site‐Selective Cascade Radical Addition of Biaryl Ynones for the Construction of Spiro‐ and Fused Carbon Rings
It is worth noting that this is the first example of alkoxycarbonyl radical addition to ynones, providing a series of novel functional derivatives. An IrIII-catalyzed cascade radical addition reaction of biaryl ynones to access two classes of carbon rings has been developed. Key to the desired transformations is the regioselective radical addition to different substituted alkyne.
Comprehensive Summary
Functionalized free radical addition/cyclization reactions represent an efficient way for introducing new functionality or coupling fragments to molecules. Ynones are good regional selectivity radical acceptors in organic synthesis, and many of bio-relevant cyclic compounds could be easily obtained by direct radical cyclization reaction. Here, we report a photocatalytic cascade radical addition of biaryl ynones, for the divergent synthesis of privileged carbon cycles. Additionally, further transformation of the multi-functional group product into a variety of other derivatives demonstrates the synthetic value of this developed method.
Stereoselective α‐Glycosylation with GlcN3 Donors Enabled Collective Syntheses of Acinetobacter baumannii Capsular Polysaccharides K43, K47 and K88 Repeating Units
A synergistic α-glycosylation method with GlcN3 as donors has been developed, which enjoys mild reaction conditions, good to high yields, and high stereoselectivities. Furthermore, collective syntheses of A. baumannii CPS K43, K47 and K88 repeating units 1—3 have been achieved for the first time via applications of this α-glycosylation method.
Comprehensive Summary
Collective syntheses of A. baumannii CPS K43, K47 and K88 repeating units have been accomplished via a new α-glycosylation method with GlcN3 as donors, which features: 1) mild reaction conditions, 2) good to high yields, 3) excellent stereoselectivities. The synthetic route also highlights an orthogonal one-pot coupling strategy on the basis of glycosyl ortho-(1-phenylvinyl)benzoates for stereoselective constructions of both 1,2-trans and 1,2-cis glycosidic bonds, precluding the issues of aglycone transfer.
Synthesis of Self‐assembled Star/Linear Block Copolymer Blends via Aqueous RAFT Dispersion Polymerization
Reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization-induced self-assembly (PISA) mediated by a binary mixture of a star-like macro-RAFT agent and a linear macro-RAFT agent is developed, allowing for the synthesis of a diverse set of self-assembled star/linear block copolymer blends.
Comprehensive Summary
Reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization-induced self-assembly (PISA) of star block copolymer and linear block copolymer using a binary mixture of a star-like macro-RAFT agent and a linear macro-RAFT agent is reported. With this formulation, star block copolymer and diblock copolymer were formed simultaneously to generate colloidally stable star/linear block copolymer assemblies. Size exclusion chromatography (SEC) analysis confirmed the presence of two types of polymers in the final samples. The molar ratio of the star-like macro-RAFT agent and the linear macro-RAFT agent has a significant impact on the morphology of polymer assemblies. It was found that increasing the amount of star-like macro-RAFT agent facilitated the formation of higher-order morphologies. Additionally, effects of other reaction parameters including the length/number of the arm of the star-like macro-RAFT agent, degree of polymer (DP), monomer concentration on the morphology of star/linear block copolymer assemblies were also investigated. We expect that this work will offer new possibilities for the scalable preparation of polymer assemblies with unique structures and functions.
Porphyrin‐BODIPY Dyad: Enhancing Photodynamic Inactivation via Antenna Effect
A porphyrin-BODIPY dyad (P-BDP) was obtained through covalent bonding, featuring a two-segment design comprising a light-harvesting antenna system connected to an energy acceptor unit. The absorption spectrum of P-BDP resulted from an overlap of the individual spectra of its constituent parts, with the fluorescence emission of the BODIPY unit experiencing significant quenching (96%) due to the presence of the porphyrin unit. Spectroscopic, computational, and redox investigations revealed a competition between photoinduced energy and electron transfer processes. The dyad demonstrated the capability to sensitize both singlet molecular oxygen and superoxide radical anions. Additionally, P-BDP effectively induced the photooxidation of L-tryptophan. In suspensions of Staphylococcus aureus cells, the dyad led to a reduction of over 3.5 log (99.99%) in cell survival following 30 min of irradiation with green light. Photodynamic inactivation caused by P-BDP was also extended to the individual bacterium level, focusing on bacterial cells adhered to a surface. This dyad successfully achieved the total elimination of the bacteria upon 20 min of irradiation. Therefore, P-BDP presents an interesting photosensitizing structure that takes advantage of the light-harvesting antenna properties of the BODIPY unit combined with porphyrin, offering potential to enhance photoinactivation of bacteria.
A Facile Access to Green Fluorescent Albumin Derivatives
A Morita-Baylis-Hillman Adduct derivative bearing a triphenylamine moiety is capable of reacting with human serum albumin shifting its emission from the blue to the green-yellow, leading to green fluorescent albumin (GFA) derivatives, and enlarging the platform of probes for fluorescent-based detection techniques. The results of investigations on the biological properties suggest that GFA retains the ability of binding drug molecules.
Abstract
A Morita-Baylis-Hillman Adduct (MBHA) derivative bearing a triphenylamine moiety was found to react with human serum albumin (HSA) shifting its emission from the blue to the green-yellow thus leading to green fluorescent albumin (GFA) derivatives and enlarging the platform of probes for aggregation-induced fluorescent-based detection techniques. A possible interaction of MBHA derivative 7 with a lipophilic pocket within the HSA structure was suggested by docking studies. DLS experiments showed that the reaction with HSA induce a conformational change of the protein contributing to the aggregation process of GFA derivatives. The results of investigations on the biological properties suggested that GFA retained the ability of binding drug molecules such as warfarin and diazepam. Finally, cytotoxicity evaluation studies suggested that, although the MBHA derivative 7 at 0.1 μg/mL affected the percentage of cell viability in comparison to the negative control, it cannot be considered cytotoxic, whereas at all the other concentrations≥0.5 μg/mL resulted cytotoxic at different extent.
Unlocking High‐Current Performance in Silicon Anode: Synergistic Phosphorus Doping and Nitrogen‐Doped Carbon Encapsulation to Enhance Lithium Diffusivity
Synergistic effect of P-dopant and N-doped carbon encapsulation on ball-milled silicon nanoparticles improved Li+ diffusivity in silicon anode by tenfold. While N-doped carbon encapsulation mainly improves Li+ diffusivity, P-dopant increases the internal conductivity and further enhances Li+ diffusivity, stabilizing the cell performance at high current densities. The anode achieves 87.32 % capacity retention after 400 cycles at 4000 mA g−1.
Abstract
The silicon (Si) offers enormous theoretical capacity as a lithium-ion battery (LIB) anode. However, the low charge mobility in Si particles hinders its application for high current loading. In this study, ball-milled phosphorus-doped Si nanoparticles encapsulated with nitrogen-doped carbon (P−Si@N−C) are employed as an anode for LIBs. P-doped Si nanoparticles are first obtained via ball-milling and calcination of Si with phosphoric acid. N-doped carbon encapsulation is then introduced via carbonization of the surfactant-assisted polymerization of pyrrole monomer on P-doped Si. While P dopant is required to support the stability at high current density, the encapsulation of Si particles with N-doped carbon is influential in enhancing the overall Li+ diffusivity of the Si anode. The combined approaches improve the anode's Li+ diffusivity up to tenfold compared to the untreated anode. It leads to exceptional anode stability at a high current, retaining 87 % of its initial capacity under a large current rate of 4000 mA g−1. The full-cell comprising P−Si@N−C anode and LiFePO4 cathode demonstrates 94 % capacity retention of its initial capacity after 100 cycles at 1 C. This study explores the effective strategies to improve Li+ diffusivity for high-rate Si-based anode.
A Computational Perspective on the Reactivity of π‐spacers in Self‐Immolative Elimination Reactions
Computational characterisation of transition states for several π-spacers adopted in self-immolative elimination reactions allows rationalising electronic effects on reaction rates, paving the way towards the in silico design of new spacers.
Abstract
The controlled release of chemicals, especially in drug delivery, is crucial, often employing “self–immolative” spacers to enhance reliability. These spacers separate the payload from the protecting group, ensuring a more controlled release. Over the years, design rules have been proposed to improve the elimination process's reaction rate by modifying spacers with electron–donating groups or reducing their aromaticity. The spacer design is critical for determining the range of functional groups released during this process. This study explores various strategies from the literature aimed at improving release rates, focusing on the electronic nature of the spacer, its aromaticity, the electronic nature of its substituents, and the leaving groups involved in the elimination reaction. Through computational analysis, I investigate activation free energies by identifying transition states for model reactions. My calculations align qualitatively with experimental results, demonstrating the feasibility and reliability of computationally pre–screening model self–immolative eliminations. This approach allows proposing optimal combinations of spacer and leaving group for achieving the highest possible release rate.
Boosting the Electrocatalytic Water Splitting Performance Using Hydrophilic Metal‐Organic Framework
The article explores the efficacy of a Pd/C@MOF-303-based electrode in improving hydrogen evolution reaction performance within an electrochemical cell. It explores the mechanism underlying this improvement.
Abstract
In this study, we employed a rapid and efficient microwave method to synthesize Metal-Organic Framework (MOF-303), which was subsequently embedded onto Palladium/Carbon (Pd/C) electrodes. The resulting hybrid material, Pd/C@MOF-303, was thoroughly characterized, and its performance in the Hydrogen Evolution Reaction (HER) was systematically investigated. The Pd/C@MOF-303 composite exhibited remarkable improvements in HER performance compared to the unmodified Pd/C electrode. At a benchmark current density of 10 mA cm−2, the overpotentials for Pd/C and Pd/C@MOF-303 were measured at 185 mV and 175 mV, respectively. This reduction in overpotential highlights the superior catalytic activity of the Pd/C@MOF-303 hybrid material in facilitating the HER. Furthermore, the Pd/C@MOF-303 electrode demonstrated enhanced HER activity, increased mass activity, and excellent charge transfer rates compared to its unmodified counterpart, Pd/C. The findings underscore the significance of the hydrophilic MOF-303 in tailoring the surface characteristics of electrocatalysts, thereby offering insights into the design principles for advanced materials with superior performance in electrochemical applications.
Kinetic Analysis of the Non‐Monotonic Response of Ethene Hydrogenation Rates to Ceria Surface Reduction
Ceria surface reduction leads to non-monotonic trends in ethene hydrogenation rates due to site requirements stipulating a balance between reduced and oxidized sites. The sensitivity of hydrogenation rates to surface reduction can be tuned by varying ceria surface termination.
Abstract
The precise effect of oxide understoichiometry on bulk oxide catalytic properties continues to remain a subject of intense investigation. Of specific interest in this regard is the role of oxygen vacancies present on bulk ceria catalysts that have recently been reported to represent a more cost-effective alternative to the more toxic and expensive catalysts used industrially for the selective hydrogenation of acetylene to ethylene. Contrasting claims as to the effect of surface reduction on hydrogenation rates exist in the open literature, with vacancy formation attributed, in separate studies, either a favorable or a deleterious role in effecting hydrogenation turnovers. We report here the non-monotonic behavior of ethene hydrogenation rates that subsumes both of these trends as a function of degree of surface reduction over a sufficiently large range of pre-reduction temperatures. Steady state transient kinetic and isotopic exchange data combined with in-situ titration experiments suggest that this non-monotonic trend can be attributed not to a change in either the kinetic relevance of specific elementary steps or the hydrogenation mechanism, but rather to site requirements that stipulate the need for two distinct, proximal sites. We also show that the sensitivity of hydrogenation rates to surface reduction can be altered by varying ceria surface termination, with the more open (110) and (100) surfaces exhibiting a less asymmetric effect of surface reduction on ethene hydrogenation rates.