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Metal-free Semiconductor Photocatalysis for sp2 C-H Functionalization with Molecular Oxygen
摘要： Designing metal-free catalysts for solar energy conversion is a long-standing challenge in semiconductor photoredox catalysis (SPC). With visible-light-responsive hexagonal boron carbon nitride (h-BCN) as a non-metal photocatalyst, this system affords C–H/N–H coupling products with broad substitution tolerance and high efficiency with molecular oxygen as the terminal oxidant. The catalyst exhibits remarkable performance for the selective C-H functionalization of electron-rich arenes to C-N products (yields up to 95%) and good stability (6 recycles). Both nitrogen heteroarenes and amine salts are competent coupling nucleophiles. Mechanically, the reactive oxygen species are superoxide anion radical (O2??) and H2O2, which are proved by electron spin resonance (ESR) data, KI-starch, and control experiments. In addition, kinetic isotope effect (KIE) experiments indicate that C–H bond cleavage is not involved in the rate limiting step. This semiconductor-based photoredox system allows for C–H amination free of any metals, ligands, strong oxidants, and additives. It provides a complementary avenue to C–H functionalizations and enables synthetic applications efficiently in a sustainable manner.
关键词： Radical,Semiconductor Photoredox Catalysis,Heterogeneous Catalysis,Visible Light,C-H Fuctionalizaition
更新于2025-09-10 09:29:36
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Metal-free visible-light photocatalytic tandem radical addition-cyclization strategy for the synthesis of sulfonyl-containing isoquinolinediones
摘要： A mild radical cascade reaction for the synthesis of sulfonyl-containing isoquinolinediones has been developed, in which sulfonyl radicals can be accessed from simple sodium sulfinates under visible light and eosin Y catalysis. This tandem approach features a broad range of substrates and functional group tolerance. With this strategy, trifluoromethylated isoquinolinedione was also obtained.
关键词： radical reaction,photocatalysis,cycloaddition,eosin Y,sodium sulfinate
更新于2025-09-10 09:29:36
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Bioinspired Radical Stetter Reaction: Radical Umpolung Enabled by Ion-Pair Photocatalysis
摘要： A bioinspired, intermolecular radical Stetter reaction of α-keto acids and aldehydes is disclosed that is contingent on a formal “radical-Umpolung” concept. Enabled by secondary amine activation, electrostatic recognition ensures that the α-ketocarboxylic acids, which function as latent acyl radicals, are proximal to the in-situ generated iminium salts. This photoactive contact ion-pair is an electron-donor-acceptor (EDA) complex, which undergoes facile single electron transfer (SET) and rapid decarboxylation prior to radical-radical recombination. Importantly, decarbonylation is mitigated via this strategy. The initial computational validation on which the process is predicated matches closely with experiment. Synergising organo- and photo-catalysis activation principles finally expands the mechanistic and synthetic scope of the classic Stetter reaction to include α,β-unsaturated aldehydes as acceptors.
关键词： ion pair,Umpolung,Stetter reaction,radical,electrostatic
更新于2025-09-10 09:29:36
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Photochemical generation of radicals from alkyl electrophiles using a nucleophilic organic catalyst
摘要： Chemists extensively use free radical reactivity for applications in organic synthesis, materials science, and life science. Traditionally, generating radicals requires strategies that exploit the bond dissociation energy or the redox properties of the precursors. Here, we disclose a photochemical catalytic approach that harnesses different physical properties of the substrate to form carbon radicals. We use a nucleophilic dithiocarbamate anion catalyst, adorned with a well-tailored chromophoric unit, to activate alkyl electrophiles via an SN2 pathway. The resulting photon-absorbing intermediate affords radicals upon homolytic cleavage induced by visible light. This catalytic SN2-based strategy, which exploits a fundamental mechanistic process of ionic chemistry, grants access to open-shell intermediates from a variety of substrates that would be incompatible with or inert to classical radical-generating strategies. We also describe how the method’s mild reaction conditions and high functional group tolerance could be advantageous for developing C–C bond-forming reactions, for streamlining the preparation of a marketed drug, for the late-stage elaboration of biorelevant compounds and for enantioselective radical catalysis.
关键词： radicals,SN2 pathway,alkyl electrophiles,photochemical,C–C bond-forming reactions,visible light,enantioselective radical catalysis,nucleophilic organic catalyst
更新于2025-09-10 09:29:36
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Complexation des acides aminés basiques arginine, histidine et lysine avec l’ADN plasmidique en solution aqueuse : participation à la capture de radicaux sous irradiation X à 1,5 keV
摘要： The chemical environment of DNA in real biological situation is complex notably due to the presence of histones, i.e. nuclear proteins which are linked approximately in equal mass balance to the DNA macromolecule to form chromatin. Histones have numerous terminal tails made up of basic (positively charged) amino acids arginine and lysine while DNA is a macro-anion which holds one negative charge per phosphate moiety all along the double-helix. As a first attempt, in this study, the complexity of the nuclear chromatin structure is mimicked through the formation of complexes made up of the basic amino acids Arg, His, Lys (which apart from His are protonated at physiological pH) and a DNA plasmid used as a probe. Those three amino acids, when free in aqueous solution are known to be effective radical scavengers, notably for the hydroxyl radical, they might therefore protect DNA against indirect effects when exposed to ionizing radiations. At fixed concentration, the scavenging capacities of free amino acids, σ, for the hydroxyl radical are typically such that σHis ≈σArg > σLys (σLys ≈ 0,1 × σArg). We have measured the yields of single strand breaks per plasmid and per Gray (χ) during exposure of aqueous solutions of complexes [amino acid –plasmid DNA] to ultra-soft X-rays (1,5 keV). At equal concentrations, the three complexed amino acids which also are present in large excess in the solutions do not exhibit DNA protection capabilities that are in line with their scavenging capacities ; we find indeed single strand break yields that follow the order χHis > χArg > χLys (χ Lys ≈ 0,01 × χArg). After having detailed our experimental protocol, we analyze the specific features of basic amino acids interactions with DNA, based on a bibliographic survey. The specificity of Arg interaction with DNA, especially its propensity to create bidentate contacts with bases (principally with the G base) makes it possible to propose a way by which high DNA single strand break damage is favored in the presence of Arg. An inter-molecular radical transfer is suggested which also seems to hold for the Lysine amino acid. As for the unexpected high single strand break yields observed with His, we suggest some possible pathways but complementary experiments still will have to be performed.
关键词： ultra-soft X-rays,chromatin,DNA,amino acids,single strand breaks,radical scavengers
更新于2025-09-10 09:29:36
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Microwave dual-mode resonators for coherent spin-photon coupling
摘要： We implement superconducting Yttrium barium copper oxide planar resonators with two fundamental modes for circuit quantum electrodynamics experiments. We first demonstrate good tunability in the resonant microwave frequencies and in their interplay, as emerges from the dependence of the transmission spectra on the device geometry. We then investigate the magnetic coupling of the resonant modes with bulk samples of 2,2-diphenyl-1-picrylhydrazyl organic radical spins. The transmission spectroscopy performed at low temperature shows that the coherent spin-photon coupling regime with the spin ensembles can be achieved by each of the resonator modes. The analysis of the results within the framework of the input-output formalism and by means of entropic measures demonstrates coherent mixing of the degrees of freedom corresponding to two remote spin ensembles and, with a suitable choice of the geometry, the approaching of a regime with spin-induced mixing of the two photon modes.
关键词： coherent spin-photon coupling,circuit quantum electrodynamics,Microwave dual-mode resonators,superconducting Yttrium barium copper oxide,2,2-diphenyl-1-picrylhydrazyl organic radical spins
更新于2025-09-10 09:29:36
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Synthesis and characterization of TiO2 co-polymeric hydrogel
摘要： In this study, TiO2 doped acrylic acid-co-vinyl pyrrolidone (AA-co-VP) composite co-polymeric hydrogel was synthesized by free radical polymerization technique. Titanium dioxide (TiO2) were chosen because of its superior properties such as high activity, chemical stability, low cost, non-toxicity, and stability during irradiation. TiO2 doping were carried out by varying mass ratios as 0.05%, 0.5% and 1%. Conversion, cross-linking and swelling values of each hydrogel were calculated. According to swelling behavior, while TiO2 dope ratio increase, swelling value was also increased. Chemical, morphological and thermal properties of hydrogels were specified by using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDX), mapping and thermogravimetric analysis (TGA-DSC) techniques. TiO2 doping provides superior properties to co-polymeric hydrogel. Hydrogels have also characteristic properties of both acrylic acid and vinyl pyrrolidone.
关键词： SEM-EDX,hydrogel,TGA-DSC,free radical polymerization,acrylic acid-co-vinyl pyrrolidone,FTIR,TiO2,swelling behavior
更新于2025-09-09 09:28:46
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Ultrasensitive Fluorescence Detection of Peroxymonosulfate Based on a Sulfate Radical-Mediated Aromatic Hydroxylation
摘要： Recently, peroxymonosulfate (PMS)-based advanced oxidation processes have exhibited broad application prospects in the field of environment. Accordingly, a simple, rapid and ultrasensitive method is highly desired for the specific recognition and accurate quantification of PMS in various aqueous solutions. In this work, SO4??-induced aromatic hydroxylation was explored, and based on that, for the first time, a novel fluorescence method was developed for the PMS determination using Co2+ as a PMS activator and benzoic acid (BA) as a chemical probe. Through a suite of spectral, chromatographic, and mass spectrometric analyses, SO4?? was proven to be the dominant radical species, and salicylic acid was identified as the fluorescent molecule. As a result, a whole radical chain reaction mechanism for the generation of salicylic acid in the BA/PMS/Co2+ system was proposed. This ?uorescence method possessed a rapid reaction equilibrium (< 1 min), an ultrahigh sensitivity (detection limit = 10 nM; quantification limit = 33 nM), an excellent specificity and a wide detection range (0–100 μM). Moreover, it performed well in the presence of possible interfering substances, including two other peroxides (i.e., peroxydisulfate and hydrogen peroxide), some common ions and organics. The detection results for real water samples further validated the practical utility of the developed fluorescence method. This work provides a new method for the specific recognition and sensitive determination of PMS in complex aqueous solutions.
关键词： benzoic acid,aromatic hydroxylation,fluorescence detection,sulfate radical,salicylic acid,peroxymonosulfate
更新于2025-09-09 09:28:46
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Enhanced Fluorescent Protein Activity in Polymer Scaffold-Stabilized Phospholipid Nanoshells Using Neutral Redox Initiator Polymerization Conditions
摘要： Phospholipid nanoshells, for example, liposomes, provide a versatile enabling platform for the development of nanometer-sized biosensors and molecular delivery systems. Utilization of phospholipid nanoshells is limited by the inherent instability in complex biological environments, where the phospholipid nanoshell may disassemble and degrade, thus releasing the contents and destroying sensor function. Polymer sca?old stabilization (PSS), wherein the phospholipid nanoshells are prepared by partitioning reactive monomers into the lipid bilayer lamella followed by radical polymerization, has emerged to increase phospholipid nanoshell stability. In this work, we investigated the e?ects of three di?erent radical initiator conditions to fabricate stable PSS-phospholipid nanoshells yet retain the activity of encapsulated model ?uorescent sensor proteins. To identify nondestructive initiation conditions, UV photoinitiation, neutral redox initiation, and thermal initiation were investigated as a function of PSS-phospholipid nanoshell stabilization and ?uorescence emission intensity of enhanced green ?uorescent protein (eGFP) and tandem dimer Tomato (td-Tomato). All three initiator approaches yielded comparably stable PSS-phospholipid nanoshells, although slight variations in PSS-phospholipid nanoshell size were observed, ranging from ca. 140 nm for unstabilized phospholipid nanoshells to 300?500 nm for PSS-phospholipid nanoshells. Fluorescence emission intensity of encapsulated eGFP was completely attenuated under thermal initiation (0% vs control), moderately attenuated under UV photoinitiation (40 ± 4% vs control), and una?ected by neutral redox initiation (97 ± 3% vs control). Fluorescence emission intensity of encapsulated td-Tomato was signi?cantly attenuated under thermal initiation (13 ± 3% vs control), moderately attenuated UV photoinitiation (64 ± 5% vs control), and una?ected by neutral redox initiation (98% ± 4% vs control). Therefore, the neutral redox initiation method provides a signi?cant advancement toward the preparation of protein-functionalized PSS-phospholipid nanoshells. These results should help to guide future applications and designs of biosensor platforms using PSS-phospholipid nanoshells and other polymer systems employing protein transducers.
关键词： Phospholipid nanoshells,td-Tomato,Neutral redox initiation,UV photoinitiation,Radical initiator conditions,eGFP,Polymer sca?old stabilization,Thermal initiation,Fluorescent sensor proteins
更新于2025-09-09 09:28:46
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Photoorganocatalytic Radical Reaction of Cinnamaldehydes and Olefins
摘要： Melchiorre and co-workers report a visible-light-mediated enantioselective radical reaction between cinnamaldehydes and a broad range of olefins that proceeds via a chiral excited-state iminium ion. The reaction was successfully extended to a three-component radical cascade reaction.
关键词： photochemistry,asymmetric radical reaction,cascade reaction,alkenes,cinnamaldehydes
更新于2025-09-09 09:28:46