Self‐Assembled Heteroleptic Zn(II) Dithiocarbamate‐Based 2D‐Interwoven Supramolecular Giant Macrocycles and Their Redox Properties

This article presents a new heteroleptic Zn(II) dithiocarbamate ( 1 ) having molecules linked together via H···H and π···π interactions to form a giant hexanuclear macrocycle. These macrocycles are connected together through S···H interactions to offer a unique two‐dimensional cloth‐like interwoven architecture in the solid state. The redox behavior of the complex deposited on the surface of a glassy carbon electrode was investigated in different pH media. The analyte was found to oxidize and reduce in a pH‐dependent irreversible manner. On the basis of the electrochemical findings, redox mechanistic pathways were proposed.     

CHOLESTERYL PHOSPHITE AND RELATED COMPOUNDS

Abstract

The preparation of cholesteryl phosphorodichloridite (2) is described; this compound with aniline (2 mol. equiv.) gave the N-phenylphosphoramidochloridite (5) and the latter by condensation with water afforded the N-phenyl-amidophosphite (6).

Similarly the N-phenylphosphoramidochloridite (5) with morpholine gave the morpholidite (7); phenylhydrazine gave the hydrazinophosphite (8) and ethanol the amidoethyl phosphite (9). Cholesteryl phosphorodichloridite (2) by reaction with aniline (4 mol. equiv.) gave the N,N ¹?diphenylphosphorodiamidite (10).

The reaction of cholesteryl phosphorodichloridite (2) with methanol and ethanol are discussed in relation to the analogous reactions with cholesteryl phosphorodichloridate. Boiling ethanol gave cholesterol as the only isolatable product but at room temperature a low yield of the diethylphosphite (11; R=Et) was obtained. The yield of the phosphite was greatly increased in the presence of base. Similarly the dichloridite 2 with boiling water gave cholesterol (1), but at room temperature cholesteryl phosphite 3 was isolated: the mechanistic basis for these different results is briefly discussed.

trans-4-t-Butylcyclohexanol with phosphorus trichloride gave the phosphorodichloridite, which was characterised by conversion to the corresponding N,N ¹?diphenylphosphorodiamidite.     

Radon concentration in drinking water sources of the region adjacent to a tectonically active Karak Thrust,southern Kohat Plateau,Khyber Pakhtunkhwa,Pakistan

A total of 84 drinking water samples from tube wells, natural springs, hand pumps and open wells in the region adjacent to a tectonically active Karak Thrust, Pakistan, were analyzed for radon content determination. These samples have a mean, maximum and minimum radon values of 9.4 ± 0.4, 25.1 ± 0.9, and 1.1 ± 0.2 Bq l^?1, respectively. This study indicates that 24 % of samples from tube wells, 44 % from springs, and 50 % from hand pumps have radon levels in excess of the EPA recommended maximum contaminant level of 11.1 Bq l^?1. The mean annual effective doses of all the samples are lower than the reference level of 0.1 mSv a^?1. Drinking water from majority of the sources within the region is generally safe as far as radon related health hazards are concerned with exception of few isolated cases.     

Decay of cystalline order and equilibration during the solid-to-plasma transition induced by 20-fs microfocused 92-eV free-electron-laser pulses

We have studied a solid-to-plasma transition by irradiating Al foils with the FLASH free electron laser at intensities up to 10(16) W/cm(2). Intense XUV self-emission shows spectral features that are consistent with emission from regions of high density, which go beyond single inner-shell photoionization of solids. Characteristic features of intrashell transitions allowed us to identify Auger heating of the electrons in the conduction band occurring immediately after the absorption of the XUV laser energy as the dominant mechanism. A simple model of a multicharge state inverse Auger effect is proposed to explain the target emission when the conduction band at solid density becomes more atomiclike as energy is transferred from the electrons to the ions. This allows one to determine, independent of plasma simulations, the electron temperature and density just after the decay of crystalline order and to characterize the early time evolution.     

The crystal structure and low temperature magnetic susceptibility of square-planar bis(1,5-diazacyclooctane)nickel(II) perchlorate dihydrate

Summary We have carried out low temperature magnetic susceptibility measurements and a redetermination of the crystal and molecular structure of bis(1,5-diazacyclooctane)nickel(II) perchlorate dihydrate from three-dimensional intensity data collected on a CAD4 diffractometer. The structure was refined by full-matrix least-squares to the R value of 6.3% for 1501 observed reflections. The positions of the hydrogen atoms were obtained from the diffraction data. Contrary to our earlier conclusions drawn by inspection of molecular models of bis(diazacyclooctane) complexes, the axial sites in the actual crystal structure are open for ligation. The Ni-N bonds are, however, sterically protected by the coplanar N-H bonds, allowing maximum ligand-field stabilization for the squareplanar geometry around the nickel atom. The observed magnetic transition from a diamagnetic state at room temperature to a paramagnetic state at 78 K is explained on the basis of long-range exchange interactions along sterically unshieldedz axis. The crystal structure is compared with other similar structures.     

Bounds on the maximum numbers of clear two-factor interactions for 2~((n1+n2)-(k1+k2)) fractional factorial split-plot designs

Fractional factorial split-plot (FFSP) designs have an important value of investigation for their special structures. There are two types of factors in an FFSP design: the whole-plot (WP) factors and sub-plot (SP) factors, which can form three types of two-factor interactions: WP2fi, WS2fi and SP2fi. This paper considers FFSP designs with resolutionⅢorⅣunder the clear effects criterion. It derives the upper and lower bounds on the maximum numbers of clear WP2fis and WS2fis for FFSP designs, and gives some methods for constructing the desired FFSP designs. It further examines the performance of the construction methods.     

形变超晶格Si/Ge的能带结构

用经验的紧束缚方法对短周期的(Si)_n/(Ge)_m形变超晶格的电子态进行了计算。结果表明,由于布里渊区折迭的要求,只有当n+m=10时超晶格才可能产生直接能隙。对周期为n+m=10的超晶格,Γ,N,△处的导带谷间的相对位置对直接能隙的形成具有决定作用,而n的大小与衬底的组分对此有极大影响。(Si)₆/(Ge)₄和(Si)₈/(Ge)₂超晶格在Si_1-xG 关键词：     

部分还原氧化石墨烯-Fe_3O_4对水中Mn(Ⅱ)的快速去除

采用改进的Hummers法制备了氧化石墨烯(GO),继而用一步共沉淀法制备了部分还原氧化石墨烯-四氧化三铁复合物(PRGO-Fe_3O_4).采用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、X射线能量色散光谱(EDX)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED)及傅里叶变换红外光谱(FTIR)等技术对其进行了分析表征;考察了p H值、接触时间、吸附材料用量、共存物质、GO的还原、循环使用次数等因素对Mn(Ⅱ)吸附行为的影响.结果表明,PRGO-Fe_3O_4中Fe_3O_4颗粒分布均匀,大小为15~20 nm,剩磁和矫顽力均很小.因Fe_3O_4颗粒的锚定作用,石墨烯片层很薄,使PRGO-Fe_3O_4对Mn(Ⅱ)表现出高效的吸附性能和良好的循环使用性能:当p H=7、PRGO-Fe_3O_4用量为500 mg/g时,对201.3211 mg/L的Mn(Ⅱ)溶液仅3 min即达吸附平衡,吸附率和吸附量分别为99.35%和404.49 mg/g,磁分离仅需10 s,经5次循环吸附后,容量保持率为首次的78%.机理与热力学研究结果表明,吸附为吸热、自发的单层化学吸附.