Search

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 3 (L = 4'-(4-methoxyphenyl)-2,2':6',2″-terpyridine) with MC, H 2 , 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 2 , and RS-PEO, respectively. After dissociation in NaOH aqueous solution, the LRuCl 3 compound can form a stable complex LRh (OH) 3 as the initial catalytically active species. Their rate-determining steps are related to the cleavage of the -C α O-H bond in both RS-Self-and RS-PEO, whereas it is associated with the heterolysis of the H-H bond in RS-H 2 . From NaOH aqueous solution, the OH - ligand of LRh(OH) 3 promotes the cleavage of the -C α O-H bond with MC and PEO as H-sources, whereas it advances the heterolysis of the H-H bond with H 2 as the H-source, owing to its strong Bro̷nsted basicity. Furthermore, the Rh center of LRh(OH) 3 mediates the cleavage of the -C α -H bond, because of its Lewis acidity. The reaction activity lowers as RS-Self > RS-PEO ≫ RS-H 2 , which is positively dependent on the protonation degree of the departing H atom. Compounds containing both -C α O-H and -C α -H groups can act as effective donors for H-sources. In the meantime, the stronger the electron-withdrawing groups they contain, the more pronounced the protonation of the -C α O-H group and the higher the reaction activity in providing H-sources. The present results provide insights into utilizing lignin's own functional groups as a hydrogen source for high-value conversion.

Aim: To evaluate the clinical effect of a new surgery technique (covering corneal stromal lenticule, CSL) for macular hole (MH) in pathological myopia., Methods: This was a prospective non-randomized series case study. Fourteen eyes of 14 patients whose axial length were more than 29 mm and suffered from MH and macular hole retinal detachment (MHRD) were included in this study. All cases were treated with 25-gauge pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling, covering CSL and C 3 F 8 gas tamponade. These cases were followed for 6mo, and the best-corrected visual acuity (BCVA), healing status of MH, the reattached rate of retinal detachment (RD), and reoperation rate were analyzed., Results: All cases were successfully performed the surgery and the postoperative follow-up was completed. After surgery, MHs were healed in all 14 eyes (100%, 14/14) after assessed by optical coherence tomography. The reattachment of retina was achieved in all 6 eyes (100%, 6/6) with MHRD. BCVA was improved in 12 eyes (85.71%, 12/14), and had no significant change in 2 eyes (14.29%, 2/14). The overall mean BCVA was improved from 1.80±0.77 to 0.82±0.46 logMAR ( F =10.46, P <0.01). No serious complications occurred in all cases., Conclusion: The new surgery technique (covering CSL) has high reattached rate of RD and high healing rate of MH in pathological myopia in the preliminary study. And it can effectively improve the visual function of patients. This new technique offers meaningful new ideas for treating refractory MH in pathological myopia., Competing Interests: Conflicts of Interest: Tang ZY, None; Qiao G, None; Zhang XJ, None; Xie LJ, None; Zou QX, None; He CM, None; Zhao L, None; Yang HQ, None; Quan Y, None; Cao K, None; Jiang H, None; He YK, None., (International Journal of Ophthalmology Press.)

Al-containing catalysts, e.g., Al(OTf) 3 , show good catalytic performance toward the conversion of cellulose to fructose in methanol solution. Here, we report the catalytic isomerization and alcoholysis mechanisms for the conversion of cellobiose to fructose at the PBE0/6-311++G(d,p), aug-cc-pVTZ theoretical level, combining the relevant experimental verifications of electrospray ionization mass spectrometry (ESI-MS), high-performance liquid chromatography (HPLC), and the attenuated total reflection-infrared (ATR-IR) spectra. From the alcoholysis of Al(OTf) 3 in methanol solution, the catalytically active species involves both the [CH 3 OH 2 ] + Brønsted acid and the [Al(CH 3 O)(OTf)(CH 3 OH) 4 ] + Lewis acid. There are two reaction pathways, i.e., one through glucose (glycosidic bond cleavage followed by isomerization, w-G ) and another through cellobiulose (isomerization followed by glycosidic bond cleavage, w-L ). The Lewis acid ([Al(CH 3 O)(OTf)(CH 3 OH) 4 ] + ) is responsible for the aldose-ketose tautomerization, while the Brønsted acid ([CH 3 OH 2 ] + ) is in charge of ring-opening, ring-closure, and glycosidic bond cleavage. For both w-G and w-L , the rate-determining steps are related to the intramolecular [1,2]-H shift between C1-C2 for the aldose-ketose tautomerization catalyzed by the [Al(CH 3 O)(OTf)(CH 3 OH) 4 ] + species. The Lewis acid ([Al(CH 3 O)(OTf)(CH 3 OH) 4 ] + ) exhibits higher catalytic activity toward the aldose-ketose tautomerization of glycosyl-chain-glucose to glycosyl-chain-fructose than that of chain-glucose to chain-fructose. Besides, the Brønsted acid ([CH 3 OH 2 ] + ) shows higher catalytic activity toward the glycosidic bond cleavage of cellobiulose than that of cellobiose. Kinetically, the w-L pathway is predominant, whereas the w-G pathway is minor. The theoretically proposed mechanism has been experimentally testified. These insights may advance on the novel design of the catalytic system toward the conversion of cellulose to fructose.

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. We performed SO removal combined with AM covering on macular area and C 3 F 8 tamponade, and phacoemulsification combined with intraocular lens implantation simultaneously cataract eyes. We followed up these patients for one year., Results: In all 17 eyes, SO was removed successfully, MHs were healed and RDs were reattached. One eye (5.89%, 1/17) had AM shifted half a month after surgery and underwent a second surgery to adjust the position of the AM and supplement C 3 F 8 . After surgery, the visual acuity (VA) improved in 15 eyes (88.24%, 15/17), no change in two eyes (11.76%, 2/17). No serious complications occurred in all eyes., Conclusion: AM covering is helpful to rescue the previous failure surgery of high myopic MH., (International Journal of Ophthalmology Press.)

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 2 + with counterpart anion in N , N -dimethylacetamide (DMA) solution have been theoretically investigated. In DMA solution, the stable VO 2 + -containing complex is the four-coordinated [V(O) 2 (DMA) 2 ] + species. For the gross reaction of 2HMF + O 2 → 2DFF + 2H 2 O, there are three main reaction stages, i.e. , the oxidation of the first HMF to DFF with the reduction of [V(O) 2 (DMA) 2 ] + to [V(OH) 2 (DMA)] + , the aerobic oxidation of [V(OH) 2 (DMA)] + to the peroxide [V(O) 3 (DMA)] + , and the oxidation of the second HMF to DFF with the reduction of [V(O) 3 (DMA)] + to [V(O) 2 (DMA) 2 ] + . The rate-determining reaction step is associated with the C-H bond cleavage of -CH 2 group of the first HMF molecule. The peroxide [V(O) 3 (DMA)] + species exhibits better oxidative activity than the initial [V(O) 2 (DMA) 2 ] + species, which originates from its narrower HOMO-LUMO gap. The counteranion Cl - exerts promotive effect on the aerobic oxidation of HMF to DFF catalyzed by [V(O) 2 (DMA) 2 ] + species., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Little is known about the detailed structural information at the interface of Pt n cluster and γ-Al 2 O 3 (001) surface, which plays an important role in the dehydrogenation and cracking of hydrocarbons. Here, the nucleation and growth of Pt n ( n = 1-8, 13) clusters on a γ-Al 2 O 3 (001) surface have been examined using density functional theory. For the most stable configuration Pt n /γ-Al 2 O 3 (001) ( n = 1-8, 13), Pt n clusters bond to the γ-Al 2 O 3 (001) surface through Pt-O and Pt-Al bonds at the expense of electron density of the Pt n cluster. With the increase in the Pt n cluster size, both the metal-support interaction and the nucleation energies exhibit an odd-even oscillation pattern, which are lower for an even Pt n cluster size than those for its adjacent odd ones. Both the metal-surface and metal-metal interactions are competitive, which control the nanoparticle morphology transition from two-dimension (2D) to three-dimension (3D). On the γ-Al 2 O 3 (001) surface, when the metal-support interaction governs, smaller clusters such as Pt 1 , Pt 2 , Pt 3 , and Pt 4 prefer a planar 2D nature. Alternatively, when the metal-metal interaction dominates, larger clusters such as Pt 5 , Pt 6 , Pt 7 , Pt 8 , and Pt 13 exhibit a two-layer structure with one or more Pt atoms on the top layer not interacting directly with the support. Herein, the Pt 4 cluster is the most stable 2D structure; Pt 5 and Pt 6 clusters are the transition from the 2D to the 3D structure; and the Pt 7 cluster is the smallest 3D structure., Competing Interests: The authors declare no competing financial interest.