‘Sacrificial’ supramolecular assembly and pressure-induced polymerization: toward sequence-defined functionalized nanothreads

Limited supramolecular strategies have been utilized to synthesize sequence-defined polymers, despite the prominence of noncovalent interactions in materials design. Herein, we illustrate the utility of ‘sacrificial’ aryl-perfluoroaryl supramolecular synthons to synthesize sp³-hybridized nanothreads from sp²-enriched reactants. Our strategy features A–B reactant pairs in the form of a phenol:pentafluorophenol co-crystal that is preorganized for an electronically-biased and sequence-defined polymerization. The polymerization, initiated at 12 GPa, affords an alternating copolymer featuring exogenous –OH functionalities. The external substitution is confirmed through IR spectroscopy. Importantly, the inclusion of the functional unit provides the first experimental glimpse at reaction mechanism: keto–enol tautomerization that can only occur during cycloaddition is observed through IR spectroscopy. Our approach realizes the first example of a functionalized nanothread and attains sequence definition through sacrificial supramolecular preorganization and presents a further approach for de novo design of complex nanothreads.

Supramolecular synthons are exploited to synthesize –OH functionalized sp³-rich sequence-defined nanothreads using pressure-induced polymerization of a phenol:pentafluorophenol co-crystal.      

Synthesis of gramicidin S and its analogues via an on-resin macrolactamization assisted by a predisposed conformation of the linear precursors

A simple and efficient preparation of gramicidin S and its analogues is described. It involves solid-phase peptide synthesis and on-resin macrolactamization without side chain protection, affording cyclic products in high yield and high purity. The high specificity of the cyclization reaction was shown to originate in the formation of a pre-organized conformation of the linear biosynthetic precursor of gramicidin S. This facile method will provide convenient access to the analogues of the natural product for functional optimization to counter microbial resistance.     

Transfer hydrogenation using recyclable polyurea-encapsulated palladium: efficient and chemoselective reduction of aryl ketones

A robust and recyclable palladium catalyst [Pd0EnCat] has been prepared by ligand exchange of polyurea-encapsulated palladium(II) acetate with formic acid, resulting in deposition of Pd(0) in the support material; Pd0EnCat is shown to be a highly efficient transfer hydrogenation catalyst for chemoselective reduction of a wide range of aryl ketones to benzyl alcohols.     

On-surface isostructural transformation from a hydrogen-bonded network to a coordination network for tuning the pore size and guest recognition

Rational manipulation of supramolecular structures on surfaces is of great importance and challenging. We show that imidazole-based hydrogen-bonded networks on a metal surface can transform into an isostructural coordination network for facile tuning of the pore size and guest recognition behaviours. Deposition of triangular-shaped benzotrisimidazole (H₃btim) molecules on Au(111)/Ag(111) surfaces gives honeycomb networks linked by double N–H⋯N hydrogen bonds. While the H₃btim hydrogen-bonded networks on Au(111) evaporate above 453 K, those on Ag(111) transform into isostructural [Ag₃(btim)] coordination networks based on double N–Ag–N bonds at 423 K, by virtue of the unconventional metal–acid replacement reaction (Ag reduces H⁺). The transformation expands the pore diameter of the honeycomb networks from 3.8 Å to 6.9 Å, giving remarkably different host–guest recognition behaviours for fullerene and ferrocene molecules based on the size compatibility mechanism.

A hydrogen-bonded network on a Ag(111) surface can transform into an isostructural Ag(i) coordination network, giving drastically different host–guest recognition behaviours.     

IMPROVED PROPERTIES OF METALLOCENE-CATALYZED LINEAR LOW-DENSITY POLYETHYLENE/POLYPROPYLENE BLENDS DURING ULTRASONIC EXTRUSION

Metallocene-catalyzed linear low-density polyethylene/polypropylene （mLLDPE/PP） blends were prepared by ultrasonic extrusion in this work. Their extrusion processing behaviors were estimated by online measured data, such as the die pressure and flow rate. Crystallization and mechanical properties of the blends were also investigated. The results show that the addition of PP improves the processing behaviors of mLLDPE, but has little effect on its mechanical properties. On the other hand, the addition of mLLDPE improves the impact strength of PP, but has little effect on its processing behavior. The processing behaviors and mechanical properties of mLLDPE/PP blends get further improved due to the presence of ultrasonic oscillation during extrusion. Compared with PP-rich blends, the apparent viscosity drop of mLLDPE-rich blends is more sensitive to ultrasonic oscillation. The ultrasonic oscillation affects the crystal nucleation, while barely the other crystalline behaviors of the blends.     

Palladium‐Catalyzed Three‐Component Coupling Reaction of Allyl Carboxylates,Norbornenes and Diboronates Involving Sequential Olefins Insertion and Borylation Reaction

An efficient Pd‐catalyzed three‐component coupling reaction of allyl carboxylates, norbornenes and diboronates is described, which allows efficient assembly of C(sp³)—C(sp³) and C(sp³)—B bonds in a single process. Moreover, this approach shows advantages of good chemo‐ and regioselectivity, as well as good substrates suitability.     

笼形聚偕胺肟树脂的研究HX／ACAO树脂吸附贵金属

氢卤酸、硝酸、硫酸、磷酸和硼酸处理的笼形聚偕胺肟树脂（ＨＸ／Ａ－ＣＡＯ）对Ａｇ＋和等贵金属离子的吸附能力按如下顺序：ＰｄＣｌ４２－：Ｈ３ＢＯ３／ＡＣＡＯ＞ＢＣＡＯ＞Ｈ３ＰＯ４／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ＞ＨＣｌ／ＡＣＡＯ＞ＨＮＯ３／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ．ＩｒＣｌ６２－：ＢＣＡＯ＞Ｈ３ＰＯ４／ＡＣＡＯ＞Ｈ３ＢＯ３／ＡＣＡＯ＞ＨＣｌ／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ≥ＨＮＯ３／ＡＣＡＯ．ＰｔＣｌ６２：ＢＣＡＯ＞Ｈ３ＢＯ３／ＡＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ＞ＨＮＯ３／ＡＣＡＯ＞ＨＣｌ／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ＞Ｈ３ＰＯ４／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ．Ａｇ＋：ＢＣＡＯ＞Ｈ３ＢＯ３／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ＞ＨＣｌ／ＡＣＡＯ＞Ｈ３ＰＯ４／ＡＣＡＯ＞ＨＮＯ３／ＡＣＡＯ．ＡｕＣｌ４－：ＢＣＡＯ＞Ｈ３ＢＯ３＞Ｈ３ＰＯ４／ＡＣＡＯ＞ＨＦ／ＡＣＡＯ＞ＨＣｌ／Ａ－ＣＡＯ＞Ｈ２ＳＯ４／ＡＣＡＯ＞ＨＩ／ＡＣＡＯ＞ＨＮＯ３／Ａ－ＣＡＯ．研究了Ｈ３ＢＯ３／ＡＣＡＯ树脂对Ａｇ＋和离子的吸附动力学，讨论了吸附机理．     

Ab initio structure determination of new compound Ba3(BO3)(PO4)

The crystal structure of new compound Ba₃BPO₇ was determined by ab initio method from high-resolution conventional X-ray powder diffraction data. The Rietveld refinement converged to R_p=5.92%, R_wp=8.87%, R_exp=5.00% with the following details: Hexagonal, space group P6₃mc, a=5.4898 (1) Å, c=14.7551(1) Å, Z=2. The basic unit of the structure is the [BaO₁₀]-[BO₃]-[PO₄] polar polyhedra-chain composed of Ba1-B-P-O cluster. These chains, running along c-axis, stack in a HCP mode to build the whole structure with triangular prism channels. The channels are parallel to c-axis too, in which Ba2 and Ba3 are located.     

Synthesis, band structure, and optical properties of Ba2ZnV2O8

A novel compound Ba₂ZnV₂O₈ has been synthesized in high temperature solution reaction and its crystal structure has been characterized by means of single crystal X-ray diffraction analysis. It crystallizes in monoclinic system and belongs to space group P2₁/c with a=7.9050(16), b=16.149(3), , β=90.49(3). It builds up from 1-D branchy chains of [ZnV₂O₈⁴⁻]_∞, and the Ba²⁺ cations are located in the space among these chains. The IR spectrum, ultraviolet-visible diffuse reflection integral spectrum and fluorescent spectra of this compound have been investigated. The calculated results of energy band structure by the density functional theory method show that the solid-state compound of Ba₂ZnV₂O₈ is an insulator with direct band gap of 3.48 eV. The calculated total and partial density of states indicate that the top valence bands are contributions from the mixings of O-2p, V-3d, and Zn-3d states and low conduction bands mostly originate from unoccupied antibonding states between the V-3d and O-2p states. The V-O bonds are mostly covalence characters and Zn-O bonds are mostly ionic interactions, and the ionic interaction strength is stronger between the Ba-O than between the Zn-O. The refractive index of n_x, n_y, and n_z is estimated to be 1.7453, 1.7469, and 1.7126, respectively, at wavelength of 1060 nm for Ba₂ZnV₂O₈ crystal.     

依波西隆蓝与蛋白质作用的共振光散射光谱及其分析应用

微量蛋白质对依波西隆蓝的共振光散射产生增强作用，且增强程度与蛋白质浓度有良好的线性关系，由此建立了测定蛋白质的灵敏共振光散射分析方法。利用该方法测定合成样品和血清样品中的蛋白质，均获得了可靠的分析结果。