Advancements and Perspectives toward Lignin Valorization via O-Demethylation

Lignin represents the largest aromatic carbon resource in plants, holding significant promise as a renewable feedstock for bioaromatics and other cyclic hydrocarbons in the context of the circular bioeconomy. However, the methoxy groups of aryl methyl ethers, abundantly found in technical lignins and lignin-derived chemicals, limit their pertinent chemical reactivity and broader applicability. Unlocking the phenolic hydroxyl functionality through O-demethylation (ODM) has emerged as a valuable approach to mitigate this need and enables further applications. In this review, we provide a comprehensive summary of the progress in the valorization of technical lignin and lignin-derived chemicals via ODM, both catalytic and non-catalytic reactions. Furthermore, a detailed analysis of the properties and potential applications of the O-demethylated products is presented, accompanied by a systematic overview of available ODM reactions. This review primarily focuses on enhancing the phenolic hydroxyl content in lignin-derived species through ODM, showcasing its potential in the catalytic funneling of lignin and value-added applications. A comprehensive synopsis and future outlook are included in the concluding section of this review.     

A phosphoranide (10-P-4) anion coordinating to transition metals,as a Lewis base and a π-acceptor

The reaction of 10-P-5 hydridophosphorane 6 with KH provides the 10-P-4 potassium phosphoranide anion 7a . Anion 7a reacts with CpFe(CO)₂I and BrAu(PEt₃) to replace the halide with the phosphoranide as a monodentate ligand forming 8 and 9 . The X-ray structure of 8 shows that the equatorial—Fe(CO)₂Cp ligand of 8 makes the apical P O bonds (1.824 Å) longer than the P O bonds (1.80 Å) of the phosphoranide oxide anion 10 . The P O bonds (1.75 Å) of 6 , with an equatorial proton ligand, are still shorter. This provides evidence that the—Fe(CO)₂Cp ligand is not only a sigma-acceptor Lewis acid ligand, but also a pi-donor that transfers electrons into the O P O three-center bond's anti-bonding orbital to increase its P—O bond lengths. It is a better pi-donor than the  O⁻ pi-donor of phosphoranide oxide 10 .     

Crystal Structure of 7-Phenyl-5,6-Dihydro-14-Aza-[1]benzopyrano[3,4-b]phenanthren-8H-One

Crystallography Reports - The crystal structure of the title compound is determined by single crystal X-ray structure analysis. The crystals are monoclinic, space group P21/c, a = 13.607(3) Å,...     

Interplay of Anion-π+ and π+-π+ Interactions in Novel Pyrido[2,1-a]isoquinolinium-Based AIEgens - Substituent- and Counterion-Dependent Fluorescence Modulation and Applications in Live Cell Mitochondrial Imaging**

Recently, the concept of anion-π⁺ interactions has witnessed unique applications in the field of AIEgen development. In this contribution, we disclose a consolidated study of a library of N-doped ionic AIEgens accessed through silver-mediated cyclization of pyridino-alkynes. A thorough photophysical, computational and crystallographic study has been conducted to rationalize the observed substituent- and counterion-dependent fluorescence properties of these luminogens. We further elucidate the prominent role of anion-π⁺ interactions, π⁺-π⁺ interactions and other non-covalent interactions, in inhibiting the undesired ACQ effect. Finally, we have also demonstrated the application of selected AIEgens for imaging of mitochondria in live cells.     

Nano-dimensional iron tungstate for super high energy density symmetric supercapacitor with redox electrolyte

Journal of Solid State Electrochemistry - In present work, we have developed 2.0 V symmetric supercapacitor with rationally prepared iron tungstate (FeWO4) nanoparticles as electrodes and...     

An Electron-Rich Helical Host for the Exclusive Removal of a Planar Electron-Deficient Organic Compound

In this study, a series of electron-rich helical hosts, viz. Pyr-HAC , Anth-HAC and Ben-HAC , containing pyrene, anthracene and benzene residues, respectively, at their periphery, were screened for their interaction with different planar electron-deficient organic guests (PEDOGs). A strong and highly selective charge-transfer interactions (CTI) was observed between the host Pyr-HAC and the guest 1,2,4,5-tetracyano-benzene (TCNB), leading to a yellow-to-bright-red color change in both the solubilized and the solid state. The interaction between Pyr-HAC and TCNB also induced profound structural and morphological changes. Pyr-HAC self-assembled into belt-like morphology created by homochiral stacking of the host molecules, but in the Pyr-HAC⊃TCNB complex, square bipyramids containing intertwined heterochiral C₂-double helices of Pyr-HAC were observed. Other PEDOGs did not induce any of the above changes in Pyr-HAC . Detailed UV/Vis absorption and fluorescence spectroscopy, NMR, and X-ray diffraction studies confirmed this selectivity, which arises due to CTI assisted by complementary, directional intermolecular hydrogen bonding (DIHB) between Pyr-HAC and TCNB. This allowed for the exclusive extraction of TCNB from a solution enriched in other PEDOGs. Thus, this study provides a ground work for designing responsive helical hosts towards CTI-driven selective “catch-and-release” of guests.