The relationship between ligand structures and their CoII and NiII complexes: Synthesis and characterization of novel dimeric CoII/CoIII complexes of bis(thiosemicarbazone)

4,6-Diacetylresorcinol serves as a starting point for the generation of multidentate S/N/O or O/N/O symmetrical chelating agents by condensation with thiosemicarbazide or semicarbazide to yield the corresponding bis(thiosemicarbazone) H₄L¹ or bis(semicarbazone) H₄L², respectively. Reaction of H₄L¹ and H₄L² with M(NO₃)₂·6H₂O (M?=?Co or Ni) afforded dimeric complexes for H₄L¹ and binuclear complexes for H₄L², revealing the tendency of S to form bridges. The dimeric cobalt complexes of H₄L¹ are very interesting in that they contain Co^II/Co^III, side/side, low-spin octahedral coordinated Co^III-ions and high-spin square-planar coordinated Co^II-ions. These complexes have the general formula [(H₂L¹)₂Co₂(H₂O) (NO₃)]·nEtOH. Arguments supporting these anomalous Co^II/Co^III structures are based on a pronounced decrease in their magnetic moments, elemental and thermal analyses, visible and IR spectra, as well as their unreactivity towards organic bases such as 1,10-phenanthroline (phen), 2,2′-bipyridine (Bpy), N,N,N′,N′-tetramethylethylenediamine (Tmen) and 8-hydroxyquinoline (oxine, Ox). The dimeric octahedral Ni^II complex [(H₂L¹)₂Ni₂(H₂O)₄]·3H₂O showed higher reactivity towards phen and Bpy and formed adducts; [(HL¹)Ni₂(B)(H₂O)₅] NO₃ (B?=?phen or Bpy). In the presence of oxine, the dimeric brown paramagnetic octahedral complex [(H₂L¹)₂Ni₂(H₂O)₄]·3H₂O was transformed to the dimeric brick-red diamagnetic square-planar complex [(H₃L¹)₂Ni₂](NO₃)₂. The latter showed dramatic behavior in its ¹H NMR spectrum in DMSO-d ₆, which was explained on the basis of H⁺-transfer. By contrast, the binuclear Ni^II–H₄L² complex (11) showed higher reactivity towards phen, Bpy and oxine. These reactions afforded mixed dimeric complexes having the molar ratio 2?:?2?:?1 (Ni^II?:?H₄L²?:?base). The binuclear Co^II–H₄L² complex afforded an adduct with phen and trinuclear complexes with Bpy and oxine. All complexes were found to be unreactive towards Tmen. Structural characterization was achieved by elemental and thermal analyses, spectral data (electronic, IR, mass and ¹H NMR spectra) and conductivity and magnetic susceptibility measurements.     

Peak shape analysis of Ag 3d core‐level X‐ray photoelectron spectra of Au@Ag core‐shell nanoparticles using an asymmetric Gaussian–Lorentzian mixed function

This article reports on the peak shape analysis of X‐ray photoelectron spectra of gold‐silver core‐shell (Au@Ag) nanoparticles (NPs) using an asymmetric Gaussian–Lorentzian mixed function. Unlike Ag NPs, Au@Ag NPs have no oxide peak and show asymmetric line shape with a high energy tail in Ag 3d core‐level spectra. A monotonic increase in the Ag 3d binding energy and a decrease in the degree of asymmetry with increasing the Ag shell thickness were observed supporting the occurrence of charge transfer from Au core to Ag shell. Copyright © 2012 John Wiley & Sons, Ltd.     

十四烷基三甲基氯化铵/十二烷基苯磺酸钠混合表面活性剂双水相体系的萃取性能

研究了十四烷基三甲基氯化铵(TTAC)与十二烷基苯磺酸钠(SDBS)混合表面活性剂水溶液双水相体系的分相情况、萃取性能及两相的微观结构.结果表明,TTAC/SDBS混合表面活性剂水溶液在30℃下能够形成稳定的双水相体系;该双水相体系对亚甲基蓝、靛红都具有一定的萃取分离作用.其上、下两相的微观结构明显不同,这是其能够形成稳定双水相体系且具有萃取作用的重要原因.     

有氧气氛中碱金属改性CuAl复合氧化物催化分解N2O的活性

合成了Cu/Al原子比分别为2.0、3.1、4.1的CuAl类水滑石样品,焙烧得到CuAl复合氧化物。在Cu/Al原子比为3.1的CuAl氧化物表面浸渍碱金属盐溶液,制备改性CuAl复合氧化物,用AES、XRD、FT-IR、BET、H₂-TPR、XPS等技术对催化剂进行了结构表征,考察了CuAl复合氧化物组成、碱金属助剂类型和K的前驱物对改性催化剂在有氧气氛中催化分解N₂O活性的影响。结果表明,Na、K、Cs改性CuAl复合氧化物均提高了催化剂活性,但K助剂的增强效应最显著;钾的不同前驱物改性CuAl复合氧化物的催化活性有显著差异,加入碳酸钾、草酸钾提高了催化剂的活性,而加入醋酸钾、硝酸钾反而降低了催化剂活性。优化出的K改性CuAl复合氧化物催化剂在含氧含水气氛的N₂O分解反应中表现出了较高的活性。     

镁铝混合氧化物负载镍催化剂上液化石油气的预重整

采用共沉淀-浸渍法并在较低温度(400～700℃)下焙烧制备了镁铝混合氧化物(MgmAl)负载的Ni催化剂.X射线衍射和程序升温还原结果表明,Ni物种高度分散于催化剂表面,没有形成尖晶石NiAl2O4.在650℃可被还原成金属Ni纳米晶粒,在400℃和较低水/碳摩尔比(S/C=2)条件下表现出较好的催化液化石油气(LP...     

拟线性抛物型积分微分方程的一个新最低阶混合元格式

对一类拟线性抛物型积分微分方程构造了一个新的最低阶三角形协调混合元格式,并直接利用单元插值的性质,给出了相应的收敛性分析和H~1-模及L~2-模意义下的最优误差估计.     

基于城乡物流一体化的连锁经营配送网络优化研究

基于城乡物流一体化的目标设定和相应基础设施平台的支持,提出连锁经营配送网络的建设模式,依据对当前连锁经营网络发展的重点工作的分析,建立了关于配送中心和农产品收购中心选择的网络优化模型.并引入算例说明模型的可行性和适用性.     

聚集数据下回归系数混合估计的相对效率

讨论在聚集数据情形下,具有附加信息的线性回归模型的参数估计,提出了回归系数的聚集混合估计,研究了该估计相对于Peter—Karsten估计和相对于最小二乘估计的相对效率,得到了相对效率的上、下界.     

基于旅客选择的高速铁路客运收益管理研究

本文旨在探讨收益管理在高速铁路客运中的应用,给出了存在多级票价时,考虑旅客选择行为的铁路客运收益管理模型,优化结果能够同时给出发车指令和座位出售限制.利用模拟数据对模型进行了数值试验,表明在不同路段长度下,考虑旅客选择行为的总收益较需求独立模型均有所提高,且随着票价等级增多而增长.     

多周期多种设备公用工程系统优化模型的改进及应用

本文提出了多周期多种设备公用工程系统改进的混合整数双线性优化模型,它含有两种优化变量和系统运行过程的离散动态约束,期望系统总设备投资(含设备折旧)与全周期运行操作费用之和最小。针对改进优化模型求解上的困难,给出将改进优化模型分解成有限多个关于连续变量的线性规划。论述了改进优化模型与分解模型的等价性以及两种模型的主要数学性质,并在此基础上提出了求解策略。最后将改进优化模型应用于某石化企业的蒸汽动力系统最优设计与运行优化集成实例。