Long-term stability and tree-ring oxidation of WSe2 using phase-contrast AFM

In this work, we use atomic force microscopy (AFM) to investigate the long-term evolution of oxidative defects of tungsten diselenide (WSe2) in ambient conditions over a period of 75 months,...

Synthesis of new representatives of 11,12-dihydro-5H-5,11-epoxybenzo[7,8]oxocino[4,3-b]pyridines – structural analogues of integrastatins A, B

The reaction of 3,5-diacetyl-2,6-dimethylpyridine with substituted salicylic aldehydes leads to the formation of the epoxybenzooxocine ring. Oxidation of the methylene group with H2SeO3 opens ways to obtaining structural analogs of natural integrastatins A, B.

Feature-Based Molecular Networking Analysis of the Metabolites Produced by in vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate

Flavan-3-ol B-ring fission derivatives (FBRFDs) are secondary metabolites that contribute to the unique properties of fermented dark teas. However, the FBRFD precursors and biochemistry are unclear. Fungal strains cultured from Fuzhuan brick tea (FBT) were incubated in an in vitro solid-state fermentation system containing β-cyclodextrin-embedded epigallocatechin gallate (EGCG), a potential precursor of FBRFDs. The produced metabolites were analyzed through a combination of targeted chromatographic isolation, non-targeted spectroscopic identification, and Feature-based Molecular Networking (FBMN) in the Global Natural Products Social Molecular Networking (GNPS) platform. Dihydromyricetin was identified for the first time, indicating that fungi possess a flavan-3-ol C-ring oxidation pathway. EGCG was verified as the precursor of dihydromyricetin and FBRFDs such as teadenol A and fuzhuanin A. The conversion was driven by the fungi rather than a hygrothermal effect. Isolates from Pezizomycotina showed much stronger abilities to convert EGCG to the B-/C-ring oxidation products than those from Saccharomycotina or Basidiomycota.

Feature-Based Molecular Networking Analysis of the Metabolites Produced by in vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate

Flavan-3-ol B-ring fission derivatives (FBRFDs) are secondary metabolites that contribute to the unique properties of fermented dark teas. However, the FBRFD precursors and biochemistry are unclear. Fungal strains cultured from Fuzhuan brick tea (FBT) were incubated in an in vitro solid-state fermentation system containing β-cyclodextrin-embedded epigallocatechin gallate (EGCG), a potential precursor of FBRFDs. The produced metabolites were analyzed through a combination of targeted chromatographic isolation, non-targeted spectroscopic identification, and Feature-based Molecular Networking (FBMN) in the Global Natural Products Social Molecular Networking (GNPS) platform. Dihydromyricetin was identified for the first time, indicating that fungi possess a flavan-3-ol C-ring oxidation pathway. EGCG was verified as the precursor of dihydromyricetin and FBRFDs such as teadenol A and fuzhuanin A. The conversion was driven by the fungi rather than a hygrothermal effect. Isolates from Pezizomycotina showed much stronger abilities to convert EGCG to the B-/C-ring oxidation products than those from Saccharomycotina or Basidiomycota.

Feature-Based Molecular Networking Analysis of the Metabolites Produced by in vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate

Flavan-3-ol B-ring fission derivatives (FBRFDs) are secondary metabolites that contribute to the unique properties of fermented dark teas. However, the FBRFD precursors and biochemistry are unclear. Fungal strains cultured from Fuzhuan brick tea (FBT) were incubated in an in vitro solid-state fermentation system containing β-cyclodextrin-embedded epigallocatechin gallate (EGCG), a potential precursor of FBRFDs. The produced metabolites were analyzed through a combination of targeted chromatographic isolation, non-targeted spectroscopic identification, and Feature-based Molecular Networking (FBMN) in the Global Natural Products Social Molecular Networking (GNPS) platform. Dihydromyricetin was identified for the first time, indicating that fungi possess a flavan-3-ol C-ring oxidation pathway. EGCG was verified as the precursor of dihydromyricetin and FBRFDs such as teadenol A and fuzhuanin A. The conversion was driven by the fungi rather than a hygrothermal effect. Isolates from Pezizomycotina showed much stronger abilities to convert EGCG to the B-/C-ring oxidation products than those from Saccharomycotina or Basidiomycota.

Non-planar core-modified dibenzi expanded isophlorin

The role of aromatic subunits is crucial to the structural and electronic properties of isophlorin and its expanded derivatives. Herein we describe the effect of benzene ring substitution in a 32[Formula: see text] expanded isophlorin core, which is at the crossroads of hexaphyrin and octaphyrin. Synthesis, structural characterization and electronic properties of a non-planar 32[Formula: see text] core-modified expanded isophlorin resembles that of a hexaphyrin like macrocycle. Dibenzi hexaphyrin is known to retain a planar structure; however, the dibenzi expanded isophlorin reported here loses its planarity and is found to adopt a unique V-shaped structure. The non-antiaromatic nature observed from spectroscopic analysis is ably supported by computational studies. Electronic absorption studies and mass spectrometry support a two-electron ring oxidation as expected of antiaromatic macrocycles.

Synthesis, spectral and electrochemical redox properties of N-methyl fused nickel(II) porphyrin

[Formula: see text]-methyl fused nickel(II) porphyrin was synthesized by a facile synthetic route in excellent yield. The effect of the electron-donating methyl group on spectral and electrochemical redox properties was analyzed by comparing the electrochemistry with that of its precursors. [Formula: see text]-methylated fused nickel(II) porphyrin exhibited a red-shifted absorption spectrum ([Formula: see text] 6–13 nm) and a 180[Formula: see text]mV anodic shift in the first ring oxidation as well as a 210[Formula: see text]mV shift in reduction with respect to its Ni(II)-fused porphyrin precursor (Ni[Formula: see text]-(NH)TPP). However, the absorption spectral features and redox potentials of N-methyl fused nickel(II) porphyrin are marginally shifted as compared to its immediate precursor, [Formula: see text]-formyl Ni(II)-fused porphyrin. Notably, Ni(II)(N-CH[Formula: see text](CHO)TPP exhibited a third oxidation at 1.51[Formula: see text]mV, corresponding to oxidation of Ni(II) to Ni(III) due to the presence of “push–pull” [Formula: see text] substituents.

Beyond the Woodward-Hoffman Rules: What Controls Reactivity in Eliminative Aromatic Ring-Forming Reactions?

The Mallory (photocyclization) and Scholl (thermal cyclohydrogenation) reactions are widely used in the synthesis of extended conjugated π systems of high scientific interest and technological importance, including molecular wires, semiconducting polymers, and nanographenes. While simple electrocyclization reactions obey the Woodward-Hoffman rules, no such simple, general, and powerful model is available for eliminative cyclization reactions due to their increased mechanistic complexity. In this work, detailed mechanistic investigations of prototypical reactions reveal that there is no single rate-determining step for thermal oxidative dehydrogenation reactions, but they are very sensitive to the presence and distribution of heteroatoms around the photocyclizing ring system. Key aspects of reactivity are correlated to the constituent ring oxidation potentials. For photocyclization reactions, planarization occurs readily and/or spontaneously following photo-excitation, and is promoted by heteroatoms within 5-membered ring adjacent to the photocyclizing site. Oxidative photocyclization requires intersystem crossing to proceed to products, while reactants configured to undergo purely eliminative photocyclization could proceed to products entirely in the excited state. Overall, oxidative photocyclization seems to strike the optimal balance between synthetic convenience (ease of preparation of reactants, mild conditions, tolerant to chemical diversity in reactants) and favourable kinetic and thermodynamic properties.

Phthalocyanine as a redox-active platform for organometallic chemistry

The first structurally characterized phthalocyanine (Pc)-based PcM-aryl, PcM–alkynyl, and PcM–Wittig complexes (with any metal centre), and the first PcCr–alkyl complexes spanning three chromium and two Pc-ring oxidation states are presented, illustrating that this classical, redox-active macrocycle can support a wide range of metal–carbon chemistry.

Mesoporous V-AlPO – New Partial Oxidation Catalyst

<p>Vanadium incorporated hexagonal mesoporous aluminophosphate characteristic of MCM-41 has been synthesized. Characterization of the catalyst has been done by using low angle XRD, N₂ adsorption, UVVIS DRS, thermal analysis, XPS and ESR spectroscopy. These techniques confirm the presence of vanadium in both +4 and +5 oxidation states in the calcined material. Liquid phase partial oxidation of toluene has been carried out on V-AlPO using 70% TBHP and 30% H₂O₂ as oxidants. When 70% TBHP is used as an oxidant, it resulted in side chain oxidation giving rise to aldehyde/acid where as with 30% H₂O₂, side chain as well as ring oxidation takes place. Catalytic activity of V-AlPO has been compared with that of VMCM-48 and other vanadium containing catalytic systems. It has been observed that mesoporous V-AlPO shows higher conversion and is also selective towards side chain oxidation products. The higher conversion of V-AlPO over V-MCM-48 has been attributed to the stabilization of the active V^+5/+4 species in AlPO framework as compared to silicate analogue.</p>