Chelating Metal Ions in a Metal-Organic Framework for Constructing a Biomimetic Catalyst Through Post-modification

Crystal engineering, as a burgeoning technology, has been widely used to construct metalloporphyrins biomimetic catalysts. Herein, a bimetallic metal-organic framework (MOF) was constructed by 4-(4-carboxyphenyl)-1,2,4-triazole ligand, Co²⁺ and Zr⁴⁺ metal ions by solvothermal reaction(named PFC-88). A N,N-chelation site was found between the two adjacent ligands in PFC-88, consequently a porphyrin-like structure was obtained through chelating Fe³⁺ in this site by post-modification, named PFC-88-Fe. The result of a single crystal X-ray technology verified that Fe ions were successfully metalated in the N,N-chelation site of PFC-88, which is assisted by the X-ray absorption near-edge structure(XANES) spectra. An o-phenylenediamine oxidation reaction was applied to assessing the catalytic activity of PFC-88-Fe, in which the absorbance increases of phenazine-2,3-diamine at λ=418 nm were recorded by absorption spectroscopy in kinetic mode, exhibiting the application potential as a biomimetic catalyst.     

气相输运沉积制备c轴择优取向的碘化铋薄膜

铋基卤化物材料因其无毒和优良的光电性能而显示出巨大的应用潜力。BiI₃作为一种层状重金属半导体,已被用于X射线检测、γ射线检测和压力传感器等领域,最近其作为一种薄膜太阳能电池吸收材料备受关注。本文采用简单的气相输运沉积(VTD)法,以BiI₃晶体粉末作为蒸发源,在玻璃基底上得到高质量c轴择优取向的BiI₃薄膜。并通过研究蒸发源温度和沉积距离对薄膜物相和形貌的影响,分析了BiI₃薄膜择优生长的机理。结果表明VTD法制备的BiI₃薄膜属于三斜晶系,其光学带隙为~1.8 eV。沉积温度对薄膜的择优取向有较大影响,在沉积温度低于270 ℃时,沉积的薄膜具有沿c轴择优取向生长的特点,超过此温度,c轴择优取向生长消失。在衬底温度为250 ℃、沉积距离为15 cm时制备的薄膜结晶性能最好,晶体形貌为片状八面体。     

A Novel Niobium Cluster Aqua Ion with Capping μ4‐Se Ligand

The aqueous solution chemistry of niobium is underexplored, and well characterized aqua complexes are scarce. In this contribution, a new niobium aqua complex was obtained by treatment of Zn‐reduced ethanolic solution of NbCl₅ with HCl in the presence of a selenide source (ZnSe). This is the first example of selenium containing aqua complex of niobium. The yellow‐green aqua complex was isolated by cation‐exchange chromatography and transformed into corresponding isothiocyanate complex by ligand exchange, which was crystallized as (PyH)_4.5[H_1.5Nb₄SeO₅(NCS)₁₀] · 0.5H₂O. X‐ray structural analysis revealed a metal‐metal bonded tetranuclear {Nb₄(μ₄‐Se)(μ₂‐O)₅}⁴⁺ core with a capping μ₄‐Se ligand.     

A Polypyridyl‐Based Layered Complex as Dual‐Functional Co‐catalyst for Photo‐Driven Organic Dyes Degradation and Water Splitting

With the ever‐increasing concerns on environmental pollution and energy crisis, it is of great urgency to develop high‐performance photocatalyst to eliminate organic pollutants from wastewater and produce hydrogen via water splitting. Herein, a polypyridyl‐based mixed covalent Cu^I/II complex with triangular {Cu₃} and rhombic {Cu₂Cl₄} subunits alternately extended by mixed SCN^– and Cl^– heterobridges [Cu₄(DNP)(SCN)Cl₄]_n ( 1 ) [DNP = 2,6‐bis(1,8‐naphthyridine‐2‐yl)pyridine] was solvothermally synthesized and employed as a dual‐functional co‐photocatalyst. Resulting from a narrowed band‐gap of 1.07 eV with suitable redox potential and unsaturated Cu^I/II sites, the complex together with H₂O₂ can effectively degrade Rhodamine B and methyl orange up to 87.4 and 88.2 %, respectively. Meanwhile, the complex mixed with H₂PtCl₆ can also accelerate the photocatalytic water splitting in the absence of a photosensitizer with the hydrogen production rate of 27.5 μmol · g^–1 · h^–1. These interesting findings may provide informative hints for the design of the multiple responsive photocatalysts.     

The Pyridazine Scaffold as a Building Block for Energetic Materials: Synthesis,Characterization, and Properties

In the present studies, the synthesis of new energetic materials based on the pyridazine scaffold and their characterization is the main subject. For this purpose, desired 3,5‐dimethoxy‐4,6‐dinitropyridazine‐1‐oxide ( 7 ) was synthesized in the first instance. The persubstituted pyridazine precursor laid the groundwork for further preparative modification. The targeted functionalization through the regioselective introduction of various smaller amine nucleophiles such as methylamine or 2‐aminoethanol gave several new energetic materials. Among them are 3,5‐bis(methylamino)‐4,6‐dinitropyridazine‐1‐oxide ( 8 ), 3,5‐bis(methylnitramino)‐4,6‐dinitropyridazine‐1‐oxide ( 9 ), 3,5‐bis(dimethylamino)‐4,6‐dinitropyridazine‐1‐oxide ( 10 ), and 3,5‐bis((2‐hydroxyethyl)amino)‐4,6‐dinitropyridazine‐1‐oxide ( 11 ). With the aim of increasing the detonation performance, compound 8 was additionally nitrated and 3,5‐bis(methylnitramino)‐4,6‐dinitropyridazine‐1‐oxide ( 9 ) was obtained. These new energetic materials were characterized and identified by multinuclear NMR (¹H, ¹³C, ¹⁴N, ¹⁵N) and IR spectroscopy, elemental analysis and mass spectrometry. In addition, their sensitivities toward impact, friction and electrostatic discharge were thoroughly examined. Furthermore, obtained single‐crystals of the substances were characterized by low‐temperature single‐crystal X‐ray diffraction.     

Structural Investigation of New Lithium Amidinates and Guanidinates

A series of potentially useful lithium amidinates and guanidinates were prepared and fully characterized. Treatment of N,N′‐diisopropylcarbodiimide with phenyllithium in diethyl ether afforded the lithium amidinate [PhC(NiPr)₂Li(OEt₂)]₂ ( 1 ). Similar treatment of N,N′‐diorganocarbodiimides R′–N=C=N–R′ [R′ = iPr, cyclohexyl (Cy)] with secondary lithium amides LiNR₂ [R₂ = Et₂, iPr₂, (CH₂)₄] followed by crystallization from THF or 1,4‐dioxane gave the lithium guanidinates [R₂NC(NR′)₂Li(S)]₂ [ 2 : R = Et, R′ = iPr, S = THF; 3 : R₂ = (CH₂)₄, R′ = iPr, S = THF; 4 : R = R′ = iPr, S = ½ 1,4‐dioxane; 5 : R₂ = (CH₂)₄, R′ = Cy, S = 1,4‐dioxane] as crystalline solids. Reaction of N‐lithioaziridine with the corresponding carbodiimides afforded solvent‐deficient [{C₂H₄NC(NiPr₂)₂}₂Li₂(THF)]₂ ( 6 ), and [C₂H₄NC(NEt)(NtBu)Li(THF)]₂ ( 7 ). Crystal structure determination revealed the presence of common ladder‐type dimeric structures for 1 – 5 . Compound 6 exists as a dimer of two ladder‐type dimers in the crystal, and 7 exhibits an unusual dimeric structure comprising an eight‐membered C₂N₄Li₂ ring.     

Evaluation of solvents’ effect on solubility,intermolecular interaction energies and habit of ascorbic acid crystals

Solubility of active pharmaceutical ingredient (API) in solvents is very important for drug development and manufacturing. Solubility data may provide further information such as thermochemical properties and intermolecular interactions that may lead to a better understanding of the formation of API crystals. In this study, solubility of ascorbic acid was determined by gravimetric method in four different commonly used polar protic solvents: water, methanol, ethanol and 2-propanol. The solubility of ascorbic acid crystal was also predicted using Conductor-like Screening Model – Realistic Solvent (COSMO-RS) approach. In this computational analysis, the generated ΔG values are based on the solubilities that were experimentally obtained to simulate the intermolecular forces. The intermolecular interaction data from COSMO-RS provide an insight into the relationship between the intermolecular interactions and its crystal habit across four different polar protic solvents. The habit of the crystals was then determined using light microscopy and scanning electron microscopy techniques, while the polymorphic form of the crystals was identified by X-ray powder diffraction and single X-ray diffraction techniques. The solubility and characterization data showed that the solvents with high polarity increased the solubility of ascorbic acid. The data also showed that different solvent polarity influenced the crystal habit, but did not change the crystal structure to form a new polymorph.     

Structure and Mechanical Stability of Epoxy Modified Polyurethane Foam Under Heat and Stress

A series of phenolic epoxy resin (PEP) modified polyurethane foams (PUF) were prepared via an in-situ polymerization, one step process. It was found that the epoxy modified PUF foam exhibited a perforated network structure with larger cell size, higher open cell porosity and enhanced ovality compared with pure PUF. With increasing content of PEP, the tensile strength, elongation at break and low temperature modulus of PUF decreased. A single T_g was observed for PEP modified PUF, indicating that the two component phases of the polyurethane-epoxy were miscible. With increasing PEP content, the T_g of PUF shifted slightly to higher temperature, tan δ_max dropped to lower values, and the retention value of the storage modulus at ?20 and ?10?°C increased. For pure PUF, the cell walls degraded and the structure became disordered after aging under heat and stress, while for PUF/20wt%PEP, the degradation degree was obviously reduced, and an orientation of the cells along the stress direction and a density increase was observed. During aging at 200?°C, the retention of the mechanical properties of PUF/20wt% PEP was much higher than that of pure PUF, and it showed superior stability under heat and stress, attributed to incorporation of the thermally resistant oxazolidone rings and benzene rings in the PU backbones, the highly cross-linked networks of the polyurethane-epoxy systems and the obvious orientation of the cells under stress.     

Crystal structures of silicon-rich lithium silicides at high pressure

Silicon (Si) is one of the most essential elements, as it is indispensable for modern electronic technology. The standard Si structure at ambient conditions is the cubic diamond structure, and it has an indirect band gap, which prevents it from being considered as a next-generation platform for semiconductor technologies. Therefore, the search for new allotropes of silicon has attracted great attention. Herein, first principles swarm-intelligence structure searches coupled with density-functional theory were performed to explore the stable high-pressure phases of silicon-rich lithium containing compounds, LiSi_x ($x=4\text{–}8$). The LiSi₄ stoichiometry was predicted to be stable, and it was found to assume one of the following space groups, P4/mnc, Cmmm, and C2/m within the pressure range of 0 to 50 GPa. By removing the Li atoms from these compounds, three silicon allotropes were obtained that were metastable at ambient pressures. Our work illustrates how novel silicon allotropes can be predicted using the CALYPSO method.     

组织忘却对组织惰性的影响研究—–环境动态性与创新导向的调节作用

组织惰性是客观存在于组织机体内的消极行为表现, 对组织的可持续发展产生阻碍作用. 如何克服组织惰性、提升组织效率是组织惰性研究的关键问题. 本文主要探讨了组织忘却对组织惰性的影响作用. 以长三角地区的260个调查样本为研究对象, 对组织忘却与组织惰性的关系进行了分析, 并探讨了环境动态性、创新导向以及环境动态性和创新导向交互在两者之间的调节作用. 结果表明 组织忘却对组织惰性具有显著的负向作用, 环境动态性和创新导向均显著正向地调节了两者之间的负向作用, 环境动态性和创新导向的交互对两者之间的关系具有调节作用, 但调节作用最强的情况出现在环境动态性或创新导向单方面较强, 而非环境动态性和创新导向两者均强时.