Theoretical investigation into coordination and selectivity of uranyl-unilateral benzotriazole salophens (X = O/S) for R/S-triadimefons

The design of new uranyl-ligands (uranyl-Ls) is of great significance for the separation and utilization of uranium. In this paper, the triazole group was introduced into uranyl-salophen (uranyl-S) to form new asymmetric uranyl-unilateral benzotriazole salophen (uranyl-UBS); we further replaced two oxygen atoms of uranyl-UBS with two sulfur atoms to generate uranyl-unilateral benzotriazole thio-salophen (uranyl-UBTS) as a new receptor. Then, we comprehensively explored coordination models of uranyl-UBS and uranyl-UBTS with R/S-triadimefons (R/S-TDFs) enantiomers as the guests using density functional theory calculations at the B3LYP//RECP/6-311G** level; we then investigated enantioselectivity recognition of the new receptors to the guests R/S-TDFs. The results indicated that the uranium atoms of the receptors uranyl-S, uranyl-UBS and uranyl-UBTS could coordinate with the carbonyl oxygens in guests R/S-TDFs to form complexes of guest-receptors R/S-TDFs-uranyl-Ls that exhibited two stable V-shaped structures with quite different properties. It was found that the coordination ability to the guests R/S-TDFs is uranyl-UBTS > uranyl-UBS > uranyl-S, while the enantioselectivity for the guests is uranyl-UBTS > uranyl-S > uranyl-UBS and, when the receptor is the same, R-TDF has stronger coordination ability than S-TDF. These results provide information and theoretical supports for the experiments of asymmetric uranyl-UBS with R/S-TDFs, and produce a reference for further exploring the coordination characteristics of asymmetric uranyl-salophen with the triazole derivatives.     

Unbridged bidentate aluminum complexes supported by diaroylhydrazone ligands: Synthesis,structure and catalysis in polymerization of ε-caprolactone and lactides

A series of novel diaroylhydrazone aluminum complexes have been synthesized and well-defined structurally, and their catalytic performance in the polymerization of ε-caprolactone and lactides have also been evaluated. Complexes [(L^1–4)₂AlMe] ( 1 – 4 ) {[L¹ = (3,5-^tBu₂–2-OMe-C₆H₂)CH=NNCOC₆H₅], [L² = (3,5-^tBu₂–2-OMe-C₆H₂)CH=NNCO(C₆H₄–4-OCH₃)], [L³ = (3,5-^tBu₂–2-OMe-C₆H₂)CH=NNCO(C₆H₄–4-Br)] and [L⁴ = (2-OMe-C₆H₄)CH=NNCO(C₆H₄–4-^tBu)]} were prepared through treatment of AlMe₃ with the corresponding proligands L^1–4H in molar ratios of 1: 1 or 1: 2. Chemical structures of all the complexes were well-defined by elemental analysis, NMR spectra as well as single-crystal X-ray study. Complexes [(L^1–4)₂AlMe] ( 1 – 4 ) in this work represent the first examples of aluminum complexes of aroylhydrazone ligands with crystallographic characterization. Specifically, they are all in monomeric form with a penta-coordinated aluminum center, including two approximately co-planar five-membered metallacycles with aluminum. Introduced bulky tert-butyl substituents in aroylhydrazone ligands could affect the geometry around the central metal which is a distorted square-based pyramid in complexes 1 – 3 while being a trigonal bipyramidal in complex 4 , thus affecting their catalytic behaviors. The complexes can successfully catalyze the ring-opening polymerization of ε-caprolactone and _L-lactide under mild conditions without any activator. In addition, complexes 1 – 4 could also polymerize rac-lactide, affording atactic polylactides with high conversions and good controllability in relatively short reaction time.     

Sustained and Controlled Release of Volatile Precursors for Chemical Vapor Deposition of Graphene at Atmospheric Pressure

Precursors and catalysts play vital roles in chemical reactions. Considerable efforts have been devoted to the investigation of catalysts for graphene growth by chemical vapor deposition in recent years. However, there has been little research on precursors because of a lack of innovation in term of creating a controllable feeding method. Herein, we present a novel sustained and controlled release approach, and develop a convenient, safe, and potentially scalable feeding system with the assistance of matrix materials and a simple portable feeder. As a result, a highly volatile liquid precursor can be fed accurately to grow large-area, uniform graphene films with optimal properties. This feeding approach will further benefit the synthesis of other two-dimensional materials from various precursors.     

Stereoselective Synthesis of the O-antigen of A. baumannii ATCC 17961 Using Long-Range Levulinoyl Group Participation

Herein, we described the first synthesis of the pentasaccharide and decasaccharide of the A. baumannii ATCC 17961 O-antigen for developing a synthetic carbohydrate-based vaccine against A. baumannii infection. The efficient synthesis of the rare sugar 2,3-diacetamido-glucuronate was achieved using our recently introduced organocatalytic glycosylation method. We found, for the first time, that long-range levulinoyl group participation via a hydrogen bond can result in a significantly improved β-selectivity in glycosylations. This solves the stereoselectivity problem of highly branched galactose acceptors. The proposed mechanism was supported by control experiments and DFT computations. Benefiting from the long-range levulinoyl group participation strategy, the pentasaccharide donor and acceptor were obtained via an efficient [2+1+2] one-pot glycosylation method and were used for the target decasaccharide synthesis.     

Cover Picture: Axis-Unfixed Biphenylphosphine-Oxazoline Ligands: Design and Applications in Asymmetric Catalytic Reactions (Chem. Rec. 10/2023)

The design and synthesis of chiral ligands plays an important role in asymmetric catalytic reactions. Over the past decades, various types of chiral phosphine-oxazolines (PHOX ligands) have been developed and have greatly advanced the field of asymmetric catalysis. Novel chiral PHOX ligand with an axis-unfixed biphenyl backbone, developed by our group, have shown interesting coordination behavior and excellent chiral inducing ability in various transition-metal-catalyzed asymmetric reactions. This personal account focuses on our developed axis-unfixed biphenylphosphine-oxazoline ligand (BiphPHOX), including an overview of its design and applications, which will provide inspiration for the exploration of novel ligands and related reactions.     

Determination of carbonate content in barite ore by headspace gas chromatography

This paper reports a method for determining the carbonate content in barite ore using headspace gas chromatography. Based on the acidification reaction, the carbonate in the barite ore was converted to CO₂ in a closed headspace vial. When the carbonate content was significant, the pressure caused changes in the CO₂ and O₂ signals and affected the measurement accuracy. It was found that carbonate content is proportional to the intensity ratio of the CO₂ to O₂ signals. Thus, the carbonate content in barite ore can be measured indirectly using a theoretical model. The results showed that the carbonate in 3 g of barite ore sample with a particle size of 74 μm could react completely with a hydrochloric acid solution (2 mol/L) at 65°C for 5 min. The method described herein had good precision (relative standard deviation < 4.14%) and accuracy (relative differences < 6.12%). Further, the limit of quantification was 0.07 mol/L. Owing to its simplicity and speed, this method can be used for the batch determination of carbonate content in barite ore.     

An Injectable Integration of Autologous Bioactive Concentrated Growth Factor and Gelatin Methacrylate Hydrogel with Efficient Growth Factor Release and 3D Spatial Structure for Accelerated Wound Healing

Growth factors are essential for wound healing owing to their multiple reparative effects. Concentrated growth factor (CGF) is a third-generation platelet extract containing various endogenous growth factors. Herein, a CGF extract solution is combined with gelatin methacrylate (GM) by physical blending to produce GM@CGF hydrogels for wound repair. The GM@CGF hydrogels show no immune rejection during autologous transplantation. Compared to CGF, GM@CGF hydrogels not only exhibit excellent plasticity and adhesivity but also prevent rapid release and degradation of growth factors. The GM@CGF hydrogels display good injectability, self-healing, swelling, and degradability along with outstanding cytocompatibility, angiogenic functions, chemotactic functions, and cell migration-promoting capabilities in vitro. The GM@CGF hydrogel can release various effective molecules to rapidly initiate wound repair, stimulate the expressions of type I collagen, transform growth factor β1, epidermal growth factor, and vascular endothelial growth factor, promote the production of granulation tissues, vascular regeneration and reconstruction, collagen deposition, and epidermal cell migration, as well as prevent excessive scar formation. In conclusion, the injectable GM@CGF hydrogel can release various growth factors and provide a 3D spatial structure to accelerate wound repair, thereby providing a foundation for the clinical application and translation of CGF.     

Bis-triarylamine with a cyclometalated diosmium bridge: A multi-stage redox-active system

A tetra(pyrid-2-yl)-pyrazine-bridged cyclometalated diosmium complex 1(PF6)2with two distal redoxactive organic amine substituents has been synthesized and characterized. This complex displays four consecutive and separated anodic redox waves at +0.24, +0.38, +0.64, and +0.71 V vs. Ag/Ag Cl. Upon stepwise oxidation, four-step absorption spectral changes in the visible to near-infrared region have been observed. The different redox states of 1(12+through 16+) can be distinguished by the significantly different absorption spectra in the visible and near-infrared region. DFT calculations of 13+show that the spin is delocalized on both osmium–amine components.     

Thermo-sensitive poly(DEGMMA-co-MEA) microgels: Synthesis,characterization and interfacial interaction with adsorbed protein layer

The novel microgels, poly[di(ethylene glycol) methyl ether methacrylate-co-2-methoxyethyl acrylate] poly(DEGMMA-co-MEA) microgels, were synthesized. The poly(DEGMMA-co-MEA) microgels were thermo-sensitive and exhibited a volume phase transitive temperature(VPTT) of 14–22 ?C. The incorporation of hydrophobic comonomer MEA shifted the VPTT of poly(DEGMMA-co-MEA) microgels to lower temperatures. The interfacial interaction of poly(DEGMMA-co-MEA) microgels and three model proteins, namely fibrinogen, bovine serum albumin and lysozyme, was investigated by quartz crystal microbalance(QCM). An injection sequence of "microgel-after-protein" was then established for the real-time study of the interaction of proteins and the microgels at their swollen and collapsed states by using QCM technique. The results indicated that the interfacial interaction of poly(DEGMMA-co-MEA) microgels and adsorbed protein layers was mainly determined by the electrostatic interaction. Because poly(DEGMMA-co-MEA) microgels were negatively charged in Tris-HCl buffer solution(p H = 7.4), the microgels did not adsorb on negatively charged fibrinogen and bovine serum albumin layers but strongly adsorbed on positively charged lysozyme layer. Stronger interaction between lysozyme and the microgels at collapsed state(i.e. at 37 ?C) was observed. Furthermore, the incorporation of MEA might weaken the interaction between poly(DEGMMA-co-MEA) microgels and proteins.