Synthesis, isomerism, and fungicidal activity against potato diseases of new (5Z)-2-(2,4,5-trioxopyrrolidin-3-ylidene)-4-oxo-1,3-thiazolidin-5-ylideneacetate derivatives with 1,3-thiazolidine-4-one ...and pyrrolidine-2,3,5-trione moieties linked by an exocyclic CC bond were described. Their structures were clearly confirmed by spectroscopic and spectrometric data (Fourier transform infrared spectroscopy, 1H and 13C nuclear magnetic resonance, and mass spectrometry), elemental analysis, and X-ray diffraction crystallography. A bioassay for antifungal activity in vitro against Phytophthora infestans, Fusariun solani, Alternaria solani, Rhizoctonia solani, and Colletotrichum coccodes demonstrated that 2,4,5-trioxopyrrolidin-1,3-thiazolidine derivatives exhibited a relatively broad spectrum of antifungal activity. One of the compounds showed considerable activity against all of the strains; in the case of F. solani, P. infestans, and A. solani, it possesses comparable or better fungicidal efficacy than the positive control Consento. Consequently, this compound is a promising fungicidal candidate for plant protection.
With photovoltaics becoming a mature, commercially feasible technology, society is willing to allocate resources for developing and deploying new technologies based on using solar light. Analysis of ...projects supported by the European Commission in the past decade indicates exponential growth of funding to photocatalytic (PC) and photoelectrocatalytic (PEC) technologies that aim either at technology readiness levels (TRLs) TRL 1–3 or TRL > 3, with more than 75 Mio€ allocated from the year 2019 onward. This review provides a summary of PC and PEC processes for the synthesis of bulk commodities such as solvents and fuels, as well as chemicals for niche applications. An overview of photoreactors for photocatalysis on a larger scale is provided. The review rounds off with the summary of reactions performed at lab scale under natural outdoor solar light to illustrate conceptual opportunities offered by solar-driven chemistry beyond the reduction of CO2 and water splitting. The authors offer their vision of the impact of this area of research on society and the economy.
Graphitic carbon nitride (g‐CN) is a transition metal free semiconductor that mediates a variety of photocatalytic reactions. Although photoinduced electron transfer is often postulated in the ...mechanism, proton‐coupled electron transfer (PCET) is a more favorable pathway for substrates possessing X−H bonds. Upon excitation of an (sp2)N‐rich structure of g‐CN with visible light, it behaves as a photobase—it undergoes reductive quenching accompanied by ion of a proton from a substrate. The results of modeling allowed us to identify active sites for PCET—the ‘triangular pockets’ on the edge facets of g‐CN. We employ excited state PCET from the substrate to g‐CN to selectively cleavethe endo‐(sp3)C−H bond in oxazolidine‐2‐ones followed by trapping the radical with O2. This reaction affords 1,3‐oxazolidine‐2,4‐diones. Measurement of the apparent pKa value and modeling suggest that g‐CN excited state can cleave X−H bonds that are characterized by bond dissociation free energy (BDFE) ≈100 kcal mol−1.
Transformation of oxazolidinones to corresponding oxazolidine‐2,4‐diones is enabled by mpg‐CN, a carbon nitride photocatalyst, using oxygen gas as an oxidant. The reaction proceeds via proton‐coupled electron transfer. The mechanism of this transformation is established by photocatalytic experiments, transient absorption spectroscopy and DFT calculations.
Following our previous studies on potassium poly(heptazine imide) (K‐PHI), that is, catalyzed photooxidative 3+2 aldoxime‐to‐nitrile addition to form 1,2,4‐oxadiazoles, we discovered that ...electron‐rich oximes yield the parent aldehydes instead of target products. In this work, the mechanism of this singlet oxygen‐mediated deoximation process was established using a series of control reactions and spectroscopic measurements such as steady‐state and time‐resolved fluorescence quenching experiments. Additionally, the singlet‐triplet energy gap value was obtained for K‐PHI in suspension, and the reaction scope was broadened to include ketoximes.
Oxime‐to‐carbonyl conversion by poly(heptazine imide)‐photocatalyzed singlet oxygen generation was studied. The mechanism was determined using steady‐state quenching, TCSPC TRES experiments and isotope labelling. The scope and possible synthetic application for chromoselective photoredox deprotection were outlined.
Two series of novel carbon nitride photocatalysts, Rho‐CN (“rhodizonate‐doped carbon nitride”) and Rho‐CN‐TC (Rho‐CN treated in potassium thiocyanate melt), are synthesized in a multistep fashion via ...copolymerization of cyanamide with potassium rhodizonate. The formed ionic carbon nitrides are composed of poly(triazine imide) (PTI/Li+Cl−) and potassium poly(heptazine imide) (K‐PHI) phases and provide a broad absorption range up to 800 nm. The photocatalysts are characterized by several techniques (including diffuse reflectance ultraviolet–visible, powder X‐ray diffraction, Fourier transform infrared, scanning electron microscopy, and electrochemical methods) and studied in a series of photocatalytic reactions, including red light‐promoted benzylamine oxidation, dual photoredox/nickel C–N cross‐coupling, and hydrogen peroxide evolution. The optimal ratio of rhodizonate dopant in its mixture with cyanamide is found to be 0.5 mol%. The performance of the newly synthesized materials is comparable to the activities of the benchmark catalysts K‐PHI and CN‐OA‐m (defective poly(heptazine imide) doped with oxamide), while not requiring more expensive nitrogen sources for preparation, like 5‐aminotetrazole, or multiple oven cycles.
Two series of heterostructured carbon nitride photocatalysts composed of poly(heptazine imide) and PTI/Li+Cl− are synthesized from cyanamide and potassium rhodizonate as a dopant. The materials have a broad absorption range, unique morphology, and are capable to act in multiple photocatalytic processes, including organic transformations and reduction of oxygen to hydrogen peroxide, and are scalable to perform as immobilized photocatalytic sheet.
Graphitisches Kohlenstoffnitrid (g‐CN) ist ein übergangsmetallfreier Halbleiter, der eine Vielzahl von photokatalytischen Reaktionen unterstützt. Obwohl oft ein photoinduzierter Elektronentransfer ...als Mechanismus postuliert wird, ist der protonengekoppelte Elektronentransfer (PCET) der bevorzugte Weg für Substrate mit X−H‐Bindungen. Bei der Anregung einer (sp2)N‐reichen Struktur von g‐CN mit sichtbarem Licht verhält sie sich wie eine Photobase – es kommt zu einem reduktivem Quenching, begleitet von der Abstraktion eines Protons aus einem Substrat. Die Ergebnisse der Modellierung ermöglichten es uns, aktive Stellen für PCET zu identifizieren – die “dreieckigen Taschen” an den Kantenfacetten von g‐CN. Excited‐State‐PCET vom Substrat zu g‐CN wurde eingesetzt um die endo‐(sp3)C−H‐Bindung in Oxazolidin‐2‐onen selektiv zu spalten, gefolgt vom Einfangen des Radikals mit O2. Diese Reaktion ergibt 1,3‐Oxazolidin‐2,4‐Dionen. Die Messung des scheinbaren pKa‐Wertes und die Modellierung deuten darauf hin, dass der angeregte g‐CN‐Zustand X−H‐Bindungen spalten kann, die durch eine freie Bindungsdissoziationsenergie (BDFE) von ≈100 kcal mol−1 gekennzeichnet sind.
Die Umwandlung von Oxazolidinonen in entsprechende Oxazolidin‐2,4‐Dione wird durch mpg‐CN, einem Kohlenstoffnitrid‐Photokatalysator, unter Verwendung von Sauerstoffgas als Oxidationsmittel ermöglicht. Die Reaktion läuft über protonengekoppelten Elektronentransfer ab. Der Mechanismus dieser Umwandlung wird durch photokatalytische Experimente, transiente Absorptionsspektroskopie und DFT‐Berechnungen ermittelt.
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