Iridium-Catalyzed Hydrogenation of a Phenoxy Radical to the Phenol: Overcoming Catalyst Deactivation with Visible Light Irradiation

Piano-stool iridium hydride complexes bearing phenylpyridine ligands are effective precatalysts for promoting the formation of element-hydrogen bonds using H2 as the stoichiometric H-atom source. Irradiation with blue light resulted in a profound enhancement of catalyst turnover for the iridium-catalyzed hydrogenation of the aryloxyl radical 2,4,6-tBu3-C6H2O• to the corresponding phenol. Monitoring the progress of the reaction revealed the formation of an iridium 3,3-dimethyl-2,3-dihydrobenzofuranyl compound arising from two C–H activation events following the proton-coupled electron transfer (PCET) step. Under thermal conditions, this compound was inactive for catalytic aryloxide hydrogenation, representing a deactivation pathway. Irradiation with blue light under H2 released the free heterocycle and regenerated the piano-stool iridium hydride precatalyst, establishing a pathway for catalyst recovery and overall enhanced turnover

<i>C</i>_S‑Symmetric Pyridine(diimine) Iron Methyl Complexes for Catalytic [2+2] Cycloaddition and Hydrovinylation: Metallacycle Geometry Determines Selectivity

A series of CS-symmetric (aryl,alkyl)-substituted pyridine(dimine) iron methyl (CyARPDI)FeCH3 complexes have been prepared, characterized, and evaluated as precatalysts for the [2+2]-cycloaddition of butadiene and ethylene. Mixtures of vinylcyclobutane and (Z)-hexa-1,4-diene were observed in each case. By comparison, C2v-symmetric, arylated (PDI) iron catalysts are exclusively selective for reversible [2+2]-cycloaddition to yield vinylcyclobutane. The alteration in the chemoselectivity of the catalytic reaction was investigated through a combination of precatalyst stability studies, identification of catalytic resting state(s), and 2H and 13C isotopic labeling experiments. While replacement of an aryl-imine substituent with an N-alkyl group decreases the stability of the formally iron(0) dinitrogen and butadiene complexes, two diamagnetic metallacycles were identified as catalyst resting states. Deuterium labeling and NOESY/EXSY NMR experiments support 1,4-hexadiene arising from catalytic hydrovinylation involving reversible oxidative cyclization leading to accessible cis-metallacycle. Cyclobutane formation proceeds by irreversible C(sp3)–C(sp3) bond-forming reductive elimination from a trans-metallacycle. These studies provide key mechanistic understanding into the high selectivity of bis(arylated) pyridine(diimine) iron catalysts for [2+2]-cycloaddition, unique, thus far, to this class of iron catalysts

Fast and Efficient Water Absorption Material Inspired by Cactus Root

Analogous to the morphological and functional features of cactus root, a novel cactus root-inspired material (CRIM) was fabricated by integrating cellulose fibers, microparticles, and agarose-based cryogels. Without undergoing sophisticated chemical synthesis or surface modification, the CRIM exhibited efficient water absorption and retention ability with high structural stability. 82% of the total water absorption capacity was recovered within 1 min, with a swelling rate nearly 930-fold faster than the evaporation rate, while only about 17% of the length extension occurred. Given that efficient water absorption and storage without physical change is crucial to the design and fabrication of water management devices, the CRIM is a promising material for various applications, including cosmetics or healthcare products, functional fabrics, and drug delivery devices

<i>C</i>_S‑Symmetric Pyridine(diimine) Iron Methyl Complexes for Catalytic [2+2] Cycloaddition and Hydrovinylation: Metallacycle Geometry Determines Selectivity

A series of CS-symmetric (aryl,alkyl)-substituted pyridine(dimine) iron methyl (CyARPDI)FeCH3 complexes have been prepared, characterized, and evaluated as precatalysts for the [2+2]-cycloaddition of butadiene and ethylene. Mixtures of vinylcyclobutane and (Z)-hexa-1,4-diene were observed in each case. By comparison, C2v-symmetric, arylated (PDI) iron catalysts are exclusively selective for reversible [2+2]-cycloaddition to yield vinylcyclobutane. The alteration in the chemoselectivity of the catalytic reaction was investigated through a combination of precatalyst stability studies, identification of catalytic resting state(s), and 2H and 13C isotopic labeling experiments. While replacement of an aryl-imine substituent with an N-alkyl group decreases the stability of the formally iron(0) dinitrogen and butadiene complexes, two diamagnetic metallacycles were identified as catalyst resting states. Deuterium labeling and NOESY/EXSY NMR experiments support 1,4-hexadiene arising from catalytic hydrovinylation involving reversible oxidative cyclization leading to accessible cis-metallacycle. Cyclobutane formation proceeds by irreversible C(sp3)–C(sp3) bond-forming reductive elimination from a trans-metallacycle. These studies provide key mechanistic understanding into the high selectivity of bis(arylated) pyridine(diimine) iron catalysts for [2+2]-cycloaddition, unique, thus far, to this class of iron catalysts

Isolation of High-Purity Extracellular Vesicles by Extracting Proteins Using Aqueous Two-Phase System

<div><p>We present a simple and rapid method to isolate extracellular vesicles (EVs) by using a polyethylene glycol/dextran aqueous two-phase system (ATPS). This system isolated more than ~75% of melanoma-derived EVs from a mixture of EVs and serum proteins. To increase the purity of EVs, a batch procedure was combined as additional steps to remove protein contaminants, and removed more than ~95% of the protein contaminants. We also performed RT-PCR and western blotting to verify the diagnostic applicability of the isolated EVs, and detected mRNA derived from melanoma cells and CD81 in isolated EVs.</p></div

Ambidextrous Polymeric Binder for Silicon Anodes in Lithium-Ion Batteries

A new type of polyamide imidazole (PAID) polymer with two functional groups for tight binding with silicon (Si) particles and carbon black is investigated as a binder for the Si anode in lithium-ion batteries (LIBs). PAID is synthesized via three reaction phases. The first phase is polyamide polymerization (p-PAID), the second phase is formation of imide and imidazole rings (i-PAID), and the last phase is ring cyclization for the PAID structure. Among these stages, i-PAID shows ambidextrous binding characteristics for LIBs. The planar π-conjugated backbone in the i-PAID provides a strong π–π stacking interaction with carbon black, thus sustaining the electrical conduction pathway in the Si electrode during cycling. The amine and carboxylic acid functional group in the i-PAID have a strong interaction with Si particles, which efficiently suppresses the volume expansion of the Si electrode, confirmed by in situ electrochemical dilatometry and ex situ SEM observation. The Si anode with the bifunctional i-PAID binder shows not only a higher reversible capacity but also a greatly enhanced cycle performance over 200 cycles in comparison to the Si anode with a simple polyimide binder. This ambidextrous polymer binder offers a new opportunity to positively impact the development of a mechanically robust Si anode for lithium-ion batteries

TEM, western blot and RT-PCR for comparison of ATPS, ATPS-Batch and ultra-centrifugation.

<p>(a) TEM image of EVs from ATPS and ultra-centrifugation method. The image did not show morphological difference between both methods. (b) The pellet after ultra-centrifugation was resuspended in 70 μl of PBS which was the same as the volume of the bottom phase of ATPS used to isolate EVs. Using the prepared samples, CD81 western blot was performed for the same sample volume (5 μl). Protein samples (5 μl) from standard mixture, ultra-centrifugation (25 μl for Ultra*5), ATPS method, and ATPS combined with Batch number 2 and 4 (ATPS-Batch #2 and #4) were used to confirm recovery efficiency. The band was brighter than that of the ultra-centrifugation method. (c) Purity of EVs was analyzed by western blot using CD81 antibody with the same protein amount (0.4 μg) from standard mixture, ultra-centrifugation, ATPS method, and ATPS-Batch #2 and #4. (d) RT-PCR was performed with 4.5 μl of isolated RNA from ultra-centrifugation, ATPS and ATPS combined with batch procedure. Bands of the house-keeping gene GAPDH and melanoma tumor marker Melan A were stronger after ATPS and ATPS-Batch than after ultra-centrifugation.</p

Recovery efficiency of EVs and proteins in batch procedure.

<p>After batch procedure, the recovery efficiency of EVs was almost unchanged while the recovery efficiency of proteins decreased.</p

Comparison of ATPS, ATPS-Batch #4 and ultra-centrifugation method.

<p>(a) Recovery efficiency. (b) Enrichment ratio.</p

Scheme and phase diagram for PEG/DEX ATPS.

<p>(a) Scheme of ATPS separation. EVs prefer DEX-phase to PEG-phase after phase separation using centrifugation (~1000ⅹg). (b) Phase diagram of PEG/DEX ATPS. The two-phase forms when system concentration is above the binodal curve.</p