Theoretical Mechanism of Rh-Containing Species Catalyzing the Hydrogenolysis of Lignin Model Compounds Using -CO-H and -C-H Groups as Superior H-Sources.

The hydrogenolysis of lignin model compounds (MCs) into high-value chemicals has received increasing attention, but their catalytic reaction mechanisms are not yet very clear. Here, we report the reaction mechanisms of the hydrogenolysis of MC into 4-acetylanisole (AAL) and guaiacol (GAL) catalyzed by LRuCl (L = 4'-(4-methoxyphenyl)-2,2':6',2″-terpyridine) with MC, H, and 1-phenylethan-1-ol (PEO) as the H-sources in aqueous solution with the Bro̷nsted base (NaOH), at the M06/def2-TZVP, 6-311++G (d,p) theoretical level, namely, RS-Self, RS-H, and RS-PEO, respectively. After dissociation in NaOH aqueous solution, the LRuCl compound can form a stable complex LRh (OH) as the initial catalytically active species.

Theoretical Insight into the Mechanism for the Cellobiose-to-Sorbitol Hydrogenation Over Diatomic Ru/NC Catalyst.

Ru/NC shows a good catalytic performance in cellobiose-to-sorbitol hydrogenation. However, the molecular origins of the selective orientation of the reaction pathway remain unclear. Here, we rationally designed the Ru/NC catalyst, for which Ru2@N8 V4 is preferred as the model.

Theoretical comparison of fructose with methylglucoside for the production of formate and levulinate catalyzed by Brønsted acids in a methanol solution.

For the conversion of fructose/methylglucoside (MG) into both methyl formate (MF) and methyl levulinate (MLev), the C-source of formate [HCOO] remains unclear at the molecular level. Herein, reaction mechanisms catalyzed by [CHOH] in a methanol solution were theoretically investigated at the PBE0/6-311++G(d,p) level. For the conversion of fructose into MF and MLev, the formate [HCOO] comes from the C1-atom of fructose, in which the rate-determining step lies in the reaction of 5-hydroxymethylfurfural (HMF) with CHOH to yield MF and MLev.

Mechanism of CO in promoting the hydrogenation of levulinic acid to γ-valerolactone catalyzed by RuCl in aqueous solution.

A Ru-containing complex shows good catalytic performance toward the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) with the assistance of organic base ligands (OBLs) and CO. Herein, we report the competitive mechanisms for the hydrogenation of LA to GVL, 4-oxopentanal (OT), and 2-methyltetrahydro-2,5-furandiol (MFD) with HCOOH or H as the H source catalyzed by RuCl in aqueous solution at the M06/def2-TZVP, 6-311++G(d,p) theoretical level. Kinetically, the hydrodehydration of LA to GVL is predominant, with OT and MFD as side products.

Cooperative Catalysis Mechanism of Brønsted and Lewis Acids from Al(OTf) with Methanol for β-Cellobiose-to-Fructose Conversion: An Experimental and Theoretical Study.

Al-containing catalysts, e.g., Al(OTf), show good catalytic performance toward the conversion of cellulose to fructose in methanol solution.

Coordination of sorbitol to Ga(OTf) in the liquid phase: an experimental and theoretical study.

In a solution of sorbitol (SBT) and Ga(OTf) compounds, the coordination of sorbitol (SBT) to [Ga(OTf)] ( = 0-3) has been investigated, using both ESI-MS spectra and density functional theory (DFT) calculations at the M06/6-311++g(d,p), aug-cc-pvtz level using a polarized continuum model (PCM-SMD). In sorbitol solution, the most stable conformer of sorbitol includes three intramolecular H-bonds, , O2H⋯O4, O4H⋯O6, and O5H⋯O3. Through ESI-MS spectra, in a tetrahydrofuran solution of both SBT and Ga(OTf) compounds, five main species are observed, , [Ga(SBT)], [Ga(OTf)], [Ga(SBT)], [Ga(OTf)(SBT)], and [Ga(OTf)(SBT)].

[NRD assisted Ilizarov technique in the treatment of infected bone and soft tissue defect of tibia].

Objective: To investigate the clinical effect of NRD assisted Ilizarov technique in the treatment of infected bone and soft tissue defect of tibia.

Methods: All 48 patients with infected bone and soft tissue defect of tibia were randomly divided into study group and control group from March 2013 to December 2020. There were 34 males and 14 females, aged from 24 to 55 years old with an average of (40.

Umbilical cord blood: A promising source for allogeneic CAR-T cells.

Chimeric antigen receptor T (CAR-T) cell therapy is an effective treatment for relapsed and refractory acute lymphoblastic leukemia (R/R ALL). However, autologous CAR-T cells derived from patients with B-ALL often show poor amplification ability, exhaustion, and anergy. To overcome these limitations, allogeneic CAR-T cells may be used as effective substitutes; however, which source would be the best substitute is unclear.

Amniotic membrane for covering high myopic macular hole associated with retinal detachment following failed primary surgery.

Aim: To evaluate the therapeutic effect of amniotic membrane (AM) for covering high myopic macular hole associated with retinal detachment following failed primary surgery.

Methods: Seventeen eyes of 17 patients whose axial length was more than 29 mm suffered from macular hole (MH) or MH associated with retinal detachment (RD), and had previously surgery of pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling and silicone oil (SO) tamponade. Half a year after the surgery, optical coherence tomography (OCT) showed that MH did not heal in all 17 eyes and RD was still maintained in 13 eyes of these 17 eyes.

Theoretical study on molecular mechanism of aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformyfuran catalyzed by VO with counterpart anion in ,-dimethylacetamide solution.

Vanadium-containing catalysts exhibit good catalytic activity toward the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformyfuran (DFF). The aerobic oxidation mechanism of HMF to DFF catalyzed by VO with counterpart anion in ,-dimethylacetamide (DMA) solution have been theoretically investigated. In DMA solution, the stable VO -containing complex is the four-coordinated [V(O)(DMA)] species.

Mechanism of Preferential Hydrogenation of Hydroxymethyl Group to Aldehyde Group in 5-Hydroxymethylfurfural over W C-Based Catalyst.

A W C cluster was used to model a W C catalyst with the armchair model of activated carbon support, noted as W C /AC. Over W C /AC, the mechanism for the hydrogenation of both -H OH and -CHO groups in 5-hydroxymethylfurfural (HMF) was theoretically studied in tetrahydrofuran at GGA-PBE/DNP level. 5-Methylfurfural was the major product from only hydrodehydration of the -CH OH group, whereas 2,5-dihydroxymethylfuran was the minor product from the hydrogenation of both -CH OH and -CHO groups.

Mechanistic study of cellobiose conversion to 5-hydroxymethylfurfural catalyzed by a Brønsted acid with counteranions in an aqueous solution.

The fundamental understanding of the cooperativity of a Brønsted acid together with its anion for cellulose conversion in an aqueous solution is limited at present, in which cellobiose has usually been regarded as a bridge that connects monosaccharides and cellulose. The mechanism of β-cellobiose conversion to 5-hydroxymethylfurfural (HMF) catalyzed by a Brønsted acid (HO) accompanied by counteranions in an aqueous solution has been studied using quantum chemical calculations at the M06-2X/6-311++G(d,p) level under a polarized continuum model (PCM-SMD). For the formation of the first HMF from cellobiose, there are three reaction pathways, i.

Molecular mechanism comparison of decarbonylation with deoxygenation and hydrogenation of 5-hydroxymethylfurfural catalyzed by palladium acetate.

The selective removal of oxygen from 5-hydroxymethylfurfural (HMF) is challenging for the effective utilization of biomass. The catalytic mechanisms of palladium acetate toward the conversion of HMF to furfuryl alcohol (FFA), 5-methylfurfural (5-MF) and 2,5-dihydroxymethyl furan (DHMF) have been theoretically investigated. The decarbonylation of HMF to FFA includes (i) migratory extrusion, (ii) metal-acetate-co-assisted deprotonation, (iii) decarbonylation, (iv) metal-assisted deprotonation, and (v) migratory extrusion and catalyst regeneration.

Regular patterns of the effects of hydrogen-containing additives on the formation of CdSe monomer.

It is unclear at the molecular level why HY (HY = RSH, or ROH, or RNH2) with HPPh2 additives kinetically affects the reaction pathway to the formation of different monomers (Ph2P-SeCd-Y or Ph2P-SeCdSe-Y) in the systhesis of semiconductor nanocrystals. In the present work, it was found that in a [Cd(OA)2 + Se[double bond, length as m-dash]P(C8H17)3 + HPPh2 + HY] mixture, HY behaves as a mediator for the formation of the initial kind of monomer, besides as a hydrogen/proton donor in the release of oleic acid and as an accelerant in the Se-P bond cleavage, which follows the mechanism of hydrogen-shift/nucleophilic-attack. The capability of the HY additive to provide a H-source decreases in the order SePPh2H > RSH > HPPh2 > ROH > RNH2, while the performance of HY to accelerate Se-P bond cleavage decreases in the order HPPh2 > RSH > RNH2 > ROH.

Density Functional Theory Study on the Nucleation and Growth of Pt Clusters on γ-AlO(001) Surface.

Little is known about the detailed structural information at the interface of Pt cluster and γ-AlO(001) surface, which plays an important role in the dehydrogenation and cracking of hydrocarbons. Here, the nucleation and growth of Pt ( = 1-8, 13) clusters on a γ-AlO(001) surface have been examined using density functional theory. For the most stable configuration Pt /γ-AlO(001) ( = 1-8, 13), Pt clusters bond to the γ-AlO(001) surface through Pt-O and Pt-Al bonds at the expense of electron density of the Pt cluster.

Insights into the Mechanistic Role of Diphenylphosphine Selenide, Diphenylphosphine, and Primary Amines in the Formation of CdSe Monomers.

The formation mechanism of CdSe monomers from the reaction of cadmium oleate (Cd(OA)2) and SePPh2H in the presence of HPPh2 and RNH2 was studied systematically at the M06//B3LYP/6-31++G(d,p),SDD level in 1-octadecene solution. Herein, SePPh2H, HPPh2, and RNH2 act as hydrogen/proton donors with a decreased capacity, leading to the release of oleic acid (RCOOH). The longer the radius of the coordinated atom is, the larger the size of the cyclic transition state is, which lowers the activation strain and the Gibbs free energy of activation for the release of RCOOH.

Theoretical Study on the Catalytic Reduction Mechanism of NO by CO on Tetrahedral Rh4 Subnanocluster.

The catalytic mechanism of 2NO + 2CO → N2 + 2CO2 on Rh4 cluster has been systematically investigated on the ground and first excited states at the B3LYP/6-311+G(2d),SDD level. For the overall reaction of 2NO + 2CO → N2 + 2CO2, the main reaction pathways take place on the facet site rather than the edge site of the Rh4 cluster. The turnover frequency (TOF) determining transition states are characteristic of the second N-O bond cleavage with rate constant k4 = 1.

Theoretical insight into the coordination of cyclic β-D-glucose to [Al(OH)(aq)](2+) and [Al(OH)2(aq)](1+) ions.

The coordination of cyclic β-D-glucose (CDG) to both [Al(OH)(aq)](2+) and [Al(OH)2(aq)](1+) ions has been theoretically investigated, using quantum chemical calculations at the PBE0/6-311++G(d,p), aug-cc-pvtz level under polarizable continuum model IEF-PCM, and molecular dynamics simulations. [Al(OH)(aq)](2+) ion prefers to form both six- and five-coordination complexes, and [Al(OH)2(aq)](+) ion to form four-coordination complex. The two kinds of oxygen atoms (on hydroxyl and ring) of CDG can coordinate to both [Al(OH)(aq)](2+) and [Al(OH)2(aq)](+) ions through single-O-ligand and double-O-ligand coordination, wherein there exists some negative charge transfer from the lone pair electron on 2p orbital of the coordinated oxygen atom to the empty 3s orbital of aluminum atom.

Activation of propane C-H and C-C bonds by gas-phase Pt atom: a theoretical study.

The reaction mechanism of the gas-phase Pt atom with C(3)H(8) has been systematically investigated on the singlet and triplet potential energy surfaces at CCSD(T)//BPW91/6-311++G(d, p), Lanl2dz level. Pt atom prefers the attack of primary over secondary C-H bonds in propane. For the Pt + C(3)H(8) reaction, the major and minor reaction channels lead to PtC(3)H(6) + H(2) and PtCH(2) + C(2)H(6), respectively, whereas the possibility to form products PtC(2)H(4) + CH(4) is so small that it can be neglected.

Hydroxylation mechanism of methane and its derivatives over designed methane monooxygenase model with peroxo dizinc core.

The peroxo dizinc Zn(2)O(2) complex Q coordinated by imidazole and carboxylate groups for each Zn center has been designed to model the hydroxylase component of methane monooxygenase (MMO) enzyme, on the basis of the experimentally available structure information of enzyme with divalent zinc ion and the MMO with Fe(2)O(2) core. The reaction mechanism for the hydroxylation of methane and its derivatives catalyzed by Q has been investigated at the B3LYP*/cc-pVTZ, Lanl2tz level in protein solution environment. These hydroxylation reactions proceed via a radical-rebound mechanism, with the rate-determining step of the C-H bond cleavage.

In vitro and in vivo effects of puerarin on promotion of osteoblast bone formation.

Objective: To assess the effect of puerarin, a natural flavonoid found in Chinese Pueraria Lobata (Wild.) Ohwi, on promotion of new bone formation.

Methods: Osteoblasts isolated from calvarial of newborn rats were cultured in vitro in the presence of puerarin at various concentrations.

Theoretical study on the gas-phase reaction mechanism between palladium monoxide and methane.

The gas-phase reaction mechanism between palladium monoxide and methane has been theoretically investigated on the singlet and triplet state potential energy surfaces (PESs) at the CCSD(T)/AVTZ//B3LYP/6-311+G(2d, 2p), SDD level. The major reaction channel leads to the products PdCH(2) + H(2)O, whereas the minor channel results in the products Pd + CH(3)OH, CH(2)OPd + H(2), and PdOH + CH(3). The minimum energy reaction pathway for the formation of main products (PdCH(2) + H(2)O), involving one spin inversion, prefers to start at the triplet state PES and afterward proceed along the singlet state PES, where both CH(3)PdOH and CH(3)Pd(O)H are the critical intermediates.