Regioselective 2′-O-debenzoylation of 2',3'-di-O-benzoyl threose nucleosides

A simple and convenient procedure for the regioselective 2′-O-debenzoylation of 2',3'-di-O-benzoyl threose nucleosides has been achieved successfully affording 3′-O-benzoyl threose nucleosides, which are useful starting material synthons for the synthesis of modified threose nucleosides for different purposes.     

Recent Developments in Alloying‐type Anode Materials for Potassium‐Ion Batteries

As an energy‐storage system, rechargeable potassium‐ion batteries (PIBs) have aroused widespread attention in recent years due to their earth abundance, low standard redox potential, and high ionic conductivity. The development of high‐performance electrode materials is key to optimize the battery performance and useful to improve the feasibility of PIB technology. In this sense, a minireview on alloying‐type anode materials for advanced PIBs is provided, covering the potassium storage properties, reaction mechanisms, theoretical analysis, electrochemical performance, and suitable binders and electrolytes.     

钾改性Mn/Ce0.65Zr0.35O2催化剂催化氧化甲苯

Volatile organic compounds (VOCs) are both harmful to human health and the environment; however, catalytic combustion offers a promising method for VOC purification because of its high efficiency without secondary pollution. Although manganese-based catalysts have been well studied for VOC catalytic oxidation, their catalytic activity at low temperature must be improved. Alkali metals as promoters have the potential to modulate the electronic and structural properties of the catalysts, improving their catalytic activity. Herein, a Ce_0.65Zr_0.35O₂ support was prepared by co-precipitation and MnO_x/Ce_0.65Zr_0.35O₂ catalysts were obtained through the incipient-wetness impregnation method. The catalytic properties of K-modified MnO_x/Ce_0.65Zr_0.35O₂ for toluene oxidation with different molar ratios of K/Mn were investigated. In addition, the catalysts were characterized by XRD, UV/visible Raman, Hydrogen temperature program reduction (H₂-TPR), Oxygen temperature programmed desorption (O₂-TPD), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance FTIR spectroscopy (DRIFTS) experiments. The results showed that alkali metal doping with K significantly improved the catalytic activity. In particular, when the molar ratio of K/Mn was 0.2, the monolith catalyst Mn/Ce_0.65Zr_0.35O₂-K-0.2 exhibited the best performance with the lowest complete conversion temperature T₉₀ of 242 ℃ at a GHSV of 12000 h⁻¹. The XRD results suggested that MnO_x was uniformly distributed on the surface of the catalyst and that Mn⁴⁺ partially reduced to Mn³⁺ on the addition of K. The Raman spectrum demonstrated that with increasing K content, both the β- and α-MnO₂ phases coexisted on the Mn/Ce_0.65Zr_0.35O₂-K-0.2 catalyst, increasing the number of surface defect sites. The H₂-TPR experiment results confirmed that Mn/Ce_0.65Zr_0.35O₂-K-0.2 exhibited the lowest reduction temperature and good reducibility. From the O₂-TPD experiments, it was clear that Mn/Ce_0.65Zr_0.35O₂-K-0.2 contained the most surface adsorbed oxygen species and excellent lattice oxygen mobility, which benefitted the toluene oxidation activity. In addition, the XPS results suggested that the content of surface adsorbed oxygen species of the Mn/Ce_0.65Zr_0.35O₂-K-0.2 catalyst was the highest among all the tested samples. In addition, toluene-TPSR in N₂ as measured by in situ DRIFTs analysis demonstrated that available lattice oxygen was present in the Mn/Ce_0.65Zr_0.35O₂-K-0.2 catalyst. Therefore, the Mn/Ce_0.65Zr_0.35O₂-K-0.2 catalyst exhibited the best redox properties and oxygen mobility of the prepared samples and showed excellent activity toward toluene oxidation. Therefore, it was concluded that the addition of an appropriate amount of K improved the redox performance of the catalyst and increased the number of surface defect sites and mobility of the lattice oxygen of the catalyst as well as the concentration of the surface active oxygen species, thereby significantly improving catalytic ability.     

Synthesis,Structure, and Stability of Lithium Arylphosphanidyl-diarylphosphane Oxide

The reaction of LiP(H)Tipp ( 2a ) and KP(H)Tipp ( 2b , Tipp = C₆H₂-2,4,6-iPr₃), which are accessible via metalation of Tipp-PH₂ ( 1 ), with bis(4-tert-butylphenyl)phosphinic chloride yields Tipp-P=P(OM)Ar₂ [M = Li ( 3a ) and K ( 3b )]. These complexes show characteristic chemical ³¹P shifts and large ¹J_PP coupling constants. These compounds degrade with elimination of the phosphinidene Tipp-P: and the alkali metal diarylphosphinites M–O–PAr₂ [M = Li ( 4a ) and K ( 4b )]. The phosphinidene forms secondary degradation products (like the meso and R,R/S,S-isomers of diphosphane Tipp-P(H)–P(H)Tipp ( 5 ) via insertion into a P–H bond of newly formed Tipp-PH₂), whereas the crystallization of [Tipp-P=P(OLi)Ar₂ · LiOPAr₂ · LiCl · 2Et₂O]₂ (i.e. [ 3a·4a· LiCl · 2Et₂O]₂) succeeds from diethyl ether. The metathesis reactions of LiP(SiiPr₃)Tipp and LiP(SiiPr₃)Mes (Mes = C₆H₂-2,4,6-Me₃) with Ar₂P(O)Cl yield Ar*-P=P(OSiiPr₃)Ar₂ (Ar* = Mes, Tipp) which degrade to Ar₂POSiiPr₃ and other secondary products.     

The crystal structure and vibrational spectra of potassium oxathioamidate

The crystal and molecular structure determination of the title compound, K–SO₂NC₂H₂,M _r=143.21, (1) is part of a series of determinations of N-substituted oxathioamidates. The structure has been refined using single-crystal X-ray diffraction data measured at 295 K [MoK-radiation with =0.71073 Å]. The crystals are orthorhombic, space group P_n2la,Z=8, with cell dimensions:a=11.399(2) Å,b=22.131(2) Å,c=4.021(1) Å,V=1014.5(7) ų.D _calc.=1.875 mg m^–3, D_obs=1.600 mg m^–3,F(000)=576, =13.14 cm^–1. The final agreement factors for 1979 observed reflections [I>3(I)] were:R=0.062 andR _w=0.067. The vibrational spectra confirm the geometrical differences between the two thiooxamidate molecules.     

Synthesis of a new potassium titanate,KTiO2(OH) by hydrothermal oxidation of Ti

Abstract

A new titanium hydroxide KTi₂O(OH) has been synthesized by hydrothermal oxidation of titanium powder in concentrated potassium hydroxide solution. A formation diagram of products synthesized in Ti-KOH-H₂O system at the region of KOH concentration from 0 to 90mol.kg-^?1-H₂O and the temperature from 150 to 350°C has been also constructed.     

Thermoluminescence of nominally pure KTaO 3 crystals

After an exposure to ultraviolet light ( u <350 v nm) at 12 v K, weak thermoluminescence of nominally pure KTaO 3 crystals was observed within the temperature region from 13 to 65 v K for the first time. An analysis of the glow curves of integral thermoluminescence revealed five glow peaks with markedly sample-dependent intensities. Three glow peaks near 26, 31, and 58 v K at the heating rate of 0.155 v K/s correspond to thermoluminescence spectrally very similar to broad-band visible photoluminescence. The glow peaks near 26 and 31 v K were assigned to the electron release from photoinduced Ta 4+ -OH m and Ta 4+ - V O centers and the glow peak near 58 v K to the hole release from photoinduced O m centers. The glow peaks near 34 and 41 v K are connected with the structureless emission band peaking near 714 v nm at 15 v K that was observed in the emission spectra of KTaO 3 crystals for the first time.     

Mn2+doping-induced-effects on commensuration and incommensuration of potassium zinc chloride crystal

Undoped and Mn²⁺-doped with different concentrations of potassium zinc chloride (KZC) crystals were grown from aqueous solutions by slow evaporation. The dielectric constant (ε), dielectric losses (tan?δ) and ac conductivity (σ_ac) of the crystals in the ferroelectric-commensurate, incommensurate and normal phases have been measured as a function of frequency, in the range 1–100?kHz, and temperature, in the range 300–580?K. Virgin samples were subjected to measurements of the frequency dependence at selected temperatures and measurements of the temperature dependence was then followed using the same samples. The increase of ε with T could be due to a combination of conductivity, structural variations and discommensuration (DC) formation and pinning as well. The increase of tan?δ with temperature was attributed to relaxation loss in addition to conduction loss, which increases more rapidly with temperature. The ac conductivity (σ_ac) and tan?δ along the polar axis of KZC increased significantly with increasing Mn²⁺ content while ε decreased. σ_ac changed with frequency according to a power law of the form σ_ac?=?f? ^s where 0.15<s<1.27. A linear decrease of ε and tan?δ with increasing the frequency was also found. The obtained results were treated by considering the effect of Mn²⁺-doping on stripples nucleation, DC evolution/annihilation, DC-lattice formation and DCs pinning by the crystal lattice and/or structural defects for virgin and thermally treated samples.     

Role of population density and increasing neighborhood in the evolution of cooperation on diluted lattices

We investigate the evolution of cooperative behaviors with increasing neighborhood size on diluted lattices. For three typical pairwise game models which include prisoner’s dilemma, snowdrift and stag hunt games, all numerical results indicate that cooperation can persist or emerge around the optimal population density which is dictated by the percolation threshold on the square lattice. Meanwhile, the neighborhood size determines the interaction ranges of focal players and then dominates the percolation threshold, and extensive numerical simulations demonstrate that the intermediate neighborhood size is the most beneficial to the evolution of cooperation in the current lattice setup. The current findings can help to deeply understand the sustenance and emergence of collective cooperation in many natural, social and economic systems.