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Science (New York, N.Y.) Jun 2024Nitrenes are a highly reactive, yet fundamental compound class. They possess a mono-valent nitrogen atom and usually a short life span, typically in the nanosecond...
Nitrenes are a highly reactive, yet fundamental compound class. They possess a mono-valent nitrogen atom and usually a short life span, typically in the nanosecond range. Here, we report on the synthesis of a stable nitrene by photolysis of the arylazide MFluindN (), which gave rise to the quantitative formation of the arylnitrene MFluindN () (MFluind = dispiro[fluorene-9,3'-(1',1',7',7'-tetramethyl-s-hydrindacen-4'-yl)-5',9''-fluorene]), that remains unchanged for at least 3 days when stored under argon atmosphere at room temperature. The extraordinary life span permitted the full characterization of by single crystal x-ray crystallography, EPR spectroscopy and SQUID magnetometry, which supported a triplet ground state. Theoretical simulations suggest in addition to the kinetic stabilization conferred by the bulky MFluind aryl substituent, that electron delocalization across the central aromatic ring contributes to the electron stabilization of .
PubMed: 38870274
DOI: 10.1126/science.adp4963 -
The Journal of Physical Chemistry. A Jun 2024Criegee intermediates exert a crucial influence on atmospheric chemistry, functioning as powerful oxidants that facilitate the degradation of pollutants, and...
Criegee intermediates exert a crucial influence on atmospheric chemistry, functioning as powerful oxidants that facilitate the degradation of pollutants, and understanding their reaction kinetics is essential for accurate atmospheric modeling. In this study, the kinetics of CHOO and -CHCHOO reactions with acetaldehyde (CHCHO) were investigated using a flash photolysis reaction tube coupled with the OH laser-induced fluorescence (LIF) method. The experimental results indicate that the reaction of -CHCHOO with CHCHO is independent of pressure in the range of 5-50 Torr when using Ar as the bath gas. However, the rate coefficient for the reaction between CHOO and CHCHO at 5.5 Torr was found to be lower compared to the near-constant values observed between 10 and 100 Torr. Furthermore, the reaction of -CHCHOO with CHCHO demonstrated positive temperature dependence from 283 to 330 K, with a rate coefficient of (2.11 ± 0.45) × 10 cm molecule s at 298 K. The activation energy and pre-exponential factor derived from the Arrhenius plot for this reaction were determined to be 2.32 ± 0.49 kcal mol and (1.66 ± 0.61) × 10 cm molecule s, respectively. In comparison, the reaction of CHOO with CHCHO exhibited negative temperature dependence, with a rate coefficient of (2.16 ± 0.39) × 10 cm molecule s at 100 Torr and 298 K and an activation energy and a pre-exponential factor of -1.73 ± 0.31 kcal mol and (1.15 ± 0.21) × 10 cm molecule s, respectively, over the temperature range of 280-333 K.
PubMed: 38868987
DOI: 10.1021/acs.jpca.4c01374 -
Environmental Geochemistry and Health Jun 2024In the pursuit of efficient photocatalytic materials for environmental applications, a new series of g-CN/N-doped CeO nanocomposites (g-CN/N-CeO NCs) was synthesized...
In the pursuit of efficient photocatalytic materials for environmental applications, a new series of g-CN/N-doped CeO nanocomposites (g-CN/N-CeO NCs) was synthesized using a straightforward dispersion method. These nanocomposites were systematically characterized to understand their structural, optical, and chemical properties. The photocatalytic performance of g-CN/N-CeO NCs was evaluated by investigating their ability to degrade methylene blue (MB) dye, a model organic pollutant. The results demonstrate that the integration of g-CN with N-doped CeO NCs reduces the optical energy gap compared to pristine N-doped CeO, leading to enhanced photocatalytic efficiency. It is benefited from the existence of g-CN/N-CeO NCs not only in promoting the charge separation and inhibits the fast charge recombination but also in improving photocatalytic oxidation performance. Hence, this study highlights the potential of g-CN/N-CeO NCs as promising candidates for various photocatalytic applications, contributing to the advancement of sustainable environmental remediation technologies.
Topics: Methylene Blue; Cerium; Nanocomposites; Catalysis; Light; Water Pollutants, Chemical; Graphite; Photochemical Processes; Photolysis; Nitrogen Compounds
PubMed: 38864996
DOI: 10.1007/s10653-024-02007-1 -
Journal of the American Chemical Society Jun 2024Boraphenalenes, compounds in which one carbon atom in the phenalenyl skeleton is replaced with a boron atom, have attracted attention for their solid-state and...
Boraphenalenes, compounds in which one carbon atom in the phenalenyl skeleton is replaced with a boron atom, have attracted attention for their solid-state and electronic structures; however, the construction of boraphenalene skeletons remains challenging because of the lack of suitable methods. Through this study, we showed that the tandem borylative cyclization of -symmetric dehydrobenzo[12]annulenes produces a new class of fully fused boron-atom-embedded polycyclic hydrocarbons possessing a 9b-boraphenalene skeleton. The obtained compounds exhibited high electron-accepting characteristics, and their two-step redox process was reversible in the reductive region, involving interconversion of 9b-boraphenalene between Hückel aromaticity and antiaromaticity. Notably, the benzo[]fluorene-fused derivative exhibited a stepwise single-crystal-to-single-crystal (SCSC) phase transition triggered by thermal annealing. Intermolecular electron coupling calculation of the crystal structures suggested a significant improvement of charge transporting ability associated with the SCSC phase transition. Moreover, adequate photoconductivity was observed for the single crystals before and after the SCSC phase transition through flash photolysis-time-resolved microwave conductivity.
PubMed: 38861619
DOI: 10.1021/jacs.4c02407 -
Chemistry (Weinheim An Der Bergstrasse,... Jun 2024A chromium complex carrying two benzanellated N-heterocyclic phosphenium (bzNHP) ligands was prepared by a salt metathesis approach. Spectroscopic studies suggest that...
A chromium complex carrying two benzanellated N-heterocyclic phosphenium (bzNHP) ligands was prepared by a salt metathesis approach. Spectroscopic studies suggest that the anellation enhances the π-acceptor ability of the NHP-units, which is confirmed by the facile electrochemical reduction of the complex to a spectroscopically characterized radical anion. Co-photolysis with H2 allowed extensive conversion into a σ-H2-complex, which shows a diverse reactivity towards donors and isomerizes under H-H bond fission and shift of a hydride to a P-ligand. The product carrying phosphenium, phosphine and hydride ligands was also synthesized independently and reacts reversibly with CO and MeCN to yield bis-phosphine complexes under concomitant Cr-to-P-shift of a hydride. In contrast, CO2 was not only bound but reduced to give an isolable formato complex, which reacted with ammonia borane under partial recovery of the metal hydride and production of formate. Further elaboration of the reactions of the chromium complexes with CO2 and NH3BH3 allowed to demonstrate the feasibility of a Cr-catalyzed transfer hydrogenation of CO2 to methanol. The various complexes described were characterized spectroscopically and in several cases by XRD studies. Further insights in reactivity patterns were provided through (spectro)electrochemical studies and DFT calculations.
PubMed: 38860887
DOI: 10.1002/chem.202401714 -
The Journal of Physical Chemistry. A Jun 2024Five biogenic unsaturated alcohols have been investigated under simulated atmospheric conditions regarding their gas-phase OH reactivity. The gas-phase rate coefficients...
Five biogenic unsaturated alcohols have been investigated under simulated atmospheric conditions regarding their gas-phase OH reactivity. The gas-phase rate coefficients of OH radicals with 2-methyl-3-buten-2-ol (), 3-methyl-2-buten-1-ol (), 3-methyl-3-buten-1-ol (), 2-methyl-3-buten-1-ol (), and 3-methyl-3-buten-2-ol () at 298 ± 2 K and 1000 ± 10 mbar total pressure of synthetic air were determined under low- and high-NO conditions using the relative kinetic technique. The present work provides for the first time the rate coefficients of gas-phase reactions of hydroxyl radicals with 2-methyl-3-buten-1-ol and 3-methyl-3-buten-2-ol. The following rate constants were measured (in 10 cm molecule s): = 6.32 ± 0.49, = 14.55 ± 0.93, = 10.04 ± 0.78, = 5.31 ± 0.37, and = 11.71 ± 1.29. No significant differences in the measured rate coefficients were obtained when either 365 nm photolysis of CHONO in the presence of NO or 254 nm photolysis of HO was used as a source of OH radicals. Reactivity toward other classes of related compounds such as alkenes and saturated alcohols is discussed. A comparison of the structure-activity relationship (SAR) estimates derived from the available accepted methodologies with experimental data available for unsaturated alcohols is provided. Atmospheric lifetimes for the investigated series of alkenols with respect to the main atmospheric oxidants are given and discussed.
PubMed: 38857889
DOI: 10.1021/acs.jpca.4c02287 -
Inorganic Chemistry Jun 2024The catalytic efficacy of the monobipyridyl (η--Cymene)Ru(II) half-metallocene, [(-Cym)Ru(bpy)Cl] was evaluated in both mixed homogeneous (dye + catalyst) and...
Photocatalytic Conversion of CO to Formate/CO by an (η--Cymene)Ru(II) Half-Metallocene Catalyst: Influence of Additives and TiO Immobilization on the Catalytic Mechanism and Product Selectivity.
The catalytic efficacy of the monobipyridyl (η--Cymene)Ru(II) half-metallocene, [(-Cym)Ru(bpy)Cl] was evaluated in both mixed homogeneous (dye + catalyst) and heterogeneous hybrid systems (dye/TiO/Catalyst) for photochemical CO reduction. A series of homogeneous photolysis experiments revealed that the (-Cym)Ru(II) catalyst engages in two competitive routes for CO reduction (CO to formate conversion via Ru-hydride vs CO to CO conversion through a Ru-COOH intermediate). The conversion activity and product selectivity were notably impacted by the p value and the concentration of the proton source added. When a more acidic TEOA additive was introduced, the half-metallocene Ru(II) catalyst leaned toward producing formate through the Ru-H mechanism, with a formate selectivity of 86%. On the other hand, in homogeneous catalysis with TFE additive, the CO-to-formate conversion through Ru-H was less effective, yielding a more efficient CO-to-CO conversion with a selectivity of >80% (TON of 140 and TON of 626 over 48 h). The preference between the two pathways was elucidated through an electrochemical mechanistic study, monitoring the fate of the metal-hydride intermediate. Compared to the homogeneous system, the TiO-heterogenized (-Cym)Ru(II) catalyst demonstrated enhanced and enduring performance, attaining TONs of 1000 for CO-to-CO and 665 for CO-to-formate.
PubMed: 38856726
DOI: 10.1021/acs.inorgchem.3c03879 -
The Journal of Physical Chemistry... Jun 2024Atmospheric new particle formation events can be driven by iodine oxides or oxoacids via both neutral and ionic mechanisms. Photolysis of new particles likely plays a...
Atmospheric new particle formation events can be driven by iodine oxides or oxoacids via both neutral and ionic mechanisms. Photolysis of new particles likely plays a significant role in their growth mechanisms, but their spectra and photolysis mechanisms remain difficult to characterize. We recorded ultraviolet (UV) photodissociation spectra of (IO)(IO) clusters, observing loss of an O atom, IO, and (IO) in the atmospherically relevant range of 300-340 nm. With increasing cluster size, the intensity of absorption red shifts and generally increases, suggesting particles photolyze more frequently as they grow. Estimates of the rates indicate that even relatively small clusters are likely to undergo photolysis under high-UV conditions. Vibrational spectra identify the covalent moiety IO as the likely chromophore, not IO. The IO loss pathway competes with particle growth, while the slower O loss pathway likely produces O + (cluster) products that could drive subsequent intraparticle chemistry, particularly with co-adsorbed organic or amine species.
PubMed: 38856106
DOI: 10.1021/acs.jpclett.4c01324 -
Journal of Hazardous Materials Aug 2024Photochemical transformation is an important attenuation process for the non-steroidal anti-inflammatory drug naproxen (NPX) in both engineered and natural waters....
Photochemical transformation is an important attenuation process for the non-steroidal anti-inflammatory drug naproxen (NPX) in both engineered and natural waters. Herein, we investigated the photolysis of NPX in aqueous solution exposed to both ultraviolet (UV, 254 nm) and natural sunlight irradiation. Results show that N purging significantly promoted NPX photolysis under UV irradiation, suggesting the formation of excited triplet state (NPX*) as a critical transient. This inference was supported by benzophenone photosensitization and transient absorption spectra. Sunlight quantum yield of NPX was only one fourteenth of that under UV irradiation, suggesting the wavelength-dependence of NPX photochemistry. NPX* formed upon irradiation of NPX underwent photodecarboxylation leading to the formation of 2-(1-hydroxyethyl)-6-methoxynaphthalene (2HE6MN), 2-(1-hydroperoxyethyl)-6-methoxynaphthalene (2HPE6MN), and 2-acetyl-6-methoxynaphthalene (2A6MN). Notably, the conjugation and spin-orbit coupling effects of carbonyl make 2A6MN a potent triplet sensitizer, therefore promoting the photodegradation of the parent NPX. In hospital wastewater, the photolysis of NPX was influenced because the photoproduct 2A6MN and wastewater components could competitively absorb photons. Bioluminescence inhibition assay demonstrated that photoproducts of NPX exhibited higher toxicity than the parent compound. Results of this study provide new insights into the photochemical behaviors of NPX during UV treatment and in sunlit surface waters.
Topics: Naproxen; Photolysis; Ultraviolet Rays; Sunlight; Water Pollutants, Chemical; Anti-Inflammatory Agents, Non-Steroidal; Benzophenones; Photosensitizing Agents
PubMed: 38852251
DOI: 10.1016/j.jhazmat.2024.134841 -
International Journal of Biological... Jun 2024Lignin-based microcapsules are extremely attractive for their biodegradability and photolysis resistance. However, the water-soluble all-lignin shells were...
Lignin-based microcapsules are extremely attractive for their biodegradability and photolysis resistance. However, the water-soluble all-lignin shells were unsatisfactory in terms of rainfall and foliar retention, and lacked the test of agricultural production practices. Herein, a novel microcapsule based on a flexible skeleton formed by interfacial polymerization and absorbed with lignin particles (LPMCs) was prepared in this study. Further analysis demonstrated that the shell was formed by cross-linking the two materials in layers and showed excellent flexibility and photolysis resistance. The pesticide loaded LPMCs showed about 98.68 % and 73.00 % improvement in scour resistance and photolysis resistance, respectively, as compared to the bare active ingredient. The foliar retention performance of LPMCs was tested in peanut plantations during the rainy season. LPMCs loaded with pyraclostrobin (Pyr) and tebuconazole (Teb) exhibited the best foliar disease control and optimum plant architecture, resulting in an increase in yield of about 5.36 %. LPMCs have a promising application prospect in the efficient pesticide utilization, by controlling its deformation, adhesion and release, an effective strategy for controlling diseases and managing plant growth was developed.
PubMed: 38851616
DOI: 10.1016/j.ijbiomac.2024.132944