Torque magnetometry study of magnetically ordered state and spin reorientation in the quasi-one-dimensional S=1/2S=1/2 Heisenberg antiferromagnet CuSb2_2O6_6

We present an experimental study of macroscopic and microscopic magnetic anisotropy of a spin tetramer system \cso using torque magnetometry and ESR spectroscopy. Large rotation of macroscopic magnetic axes with temperature observed from torque magnetometry agrees reasonably well with the rotation of the $\mathbf{g}$ tensor above $T \gtrsim 50$~K. Below 50~K, the $\mathbf{g}$ tensor is temperature independent, while macroscopic magnetic axes continue to rotate. Additionally, the susceptibility anisotropy has a temperature dependence which cannot be reconciled with the isotropic Heisenberg model of interactions between spins. ESR linewidth analysis shows that anisotropic exchange interaction must be present in \csos. These findings strongly support the presence of anisotropic exchange interactions in the Hamiltonian of the studied system. Below $T_N=8$~K, the system enters a long - range antiferromagnetically ordered state with easy axis along the $^*$ direction. Small but significant rotation of magnetic axes is also observed in the antiferromagnetically ordered state suggesting strong spin-lattice coupling in this system.Comment: 10 pages, 10 figure

A Folded Conformation of 1,4,8,11-Tetrathiacyclotetradecane in its Mercury Compound: l,4,8,11-Tetrathiacyclotetradecanedipicratomercury( II) Heminitromethane, [Hg(C10H20S4)· (C6H2N307)2] · 1/2CH3N02

The crystals of 1,4,8,11-tetrathiacyclotetradecanedipicratomercury( II) heminitromethane, [Hg(C10H20S4) · (CsH2Ns01h] · 1/2CHsN02, are triclinic, spcrce group Pl with a = 1.2794(6), b = 1.3108(5), c = = 1.0090(3) nm, a= 92.85(3) 0 , fJ = 107.67(3)0 , y = 94.54(4) 0 , V = 1.60236 nm3, and Z = 2. The structure was solved by the heavy atom method and refined by the least-squares method to R = 0.030 for the 7321 unique reflections. It consists of discrete, well separated molecules. Coordination of the mercury atom is a distorted octahedron with four sulfur atoms (Hg-S distances are 245.8(1), 251.9(1), 262 .. 9(2), and 305.0(2) pm) from the macrocycle and two oxygen moms (Hg-0 distances are 253.1(3) and 255.8(3) pm) from the two picrates. The macrocycle is folded so that three sulfur atoms with short Hg-S bonds are in an equatorial and the fourth in an apical position. The conformation of the coordinated macrocycle is compared to the conformation of cyclotetradecane at 116 K and to the conformation of the free crysta-lline macrocycle

Mechanochemical Synthesis of Alkaline Earth Mg – Ba Saccharinates. Connectivity in the Crystal Structures of Mg(sac)2∙7H2O, Ca(sac)2∙7H2O and Ba(sac)2∙4.5H2O (sac = saccharinate)

Alkaline earth saccharinates Mg – Ba were synthesized by the known solution-based methods and also by mechanochemical synthesis. The compounds were characterized by TG/DSC, X-ray powder diffraction, and Mg, Ca and Ba saccharinates by single-crystal X-ray analysis. The structure of Mg(sac)2∙7H2O (sac = saccharinate), is known but the diffraction data were collected at 170 K in this study for comparison with other structures. Crystals of hydrates of Ca – Ba saccharinates are very thin needle-like. A 4 μm crystal of Ca(sac)2∙7H2O gave a low intensity diffraction pattern of sufficient quality to locate non-hydrogen atoms (triclinic crystal system, space group P-1, Z = 4). Crystals of strontium saccharinate were too thin for data collection, however the formula Sr(sac)2∙4H2O, proposed in a previous publication was confirmed by thermogravimetric analysis. Diffraction from a 12 μm thick crystal of Ba(sac)2∙4.5H2O resulted in a complete data set (monoclinic crystal system, space group P2/c, Z = 8). In the corresponding structures, the Mg ion is six-coordinated forming an octahedron, both Ca ions are irregularly eight-coordinated with the polyhedra bridged by saccharinate ions into chains, whereas both Ba ions are irregularly nine-coordinated with the polyhedra sharing edges and corners through bridging water molecules and bridging saccharinate ions into double chains. All water molecules are included into hydrogen bonding into layers with only van der Waals and weak C–H∙∙∙O bonds between the chains

Effect of Hydrogen Bonding on the Pyramidalization of the Amino Group: Structure of 3,4-diaminobenzamidinium Chloride

3,4-diaminobenzamidinium was synthesized and spectroscopically and structurally characterized, both at room temperature and at 150 K. The crystal structure consists of two 3,4- diaminobenzamidinium cations and two chloride anions. The planar amidinium group is inclined by 35.35(5)° and 28.96(7)° in respect to the diaminobenzene moiety in the two crystallographically independent cations. The ions are interconnected by a large network of hydrogen bonds into a threedimensional structure. Pyramidalization of the amino group in relation to the hydrogen bond length in which the amino group is an acceptor is analized. Two amino groups are acceptors of N–H···N hydrogen bonds of 2.9565(14) Å and 2.9654(15) Å resulting in pyramidalization of 340(1)° and 337(1)°, respectively (the sum of the amino group bond angles is given as a measure of pyramidalization). A very weak hydrogen bond to one amino group results in a very flat pyramid (351(1)°), while one amino group is not acceptor of a hydrogen bonds and it is planar. The resonance effect has influence on the planar amino groups resulting in a shorter C–N(amino group) bond length than in the pyramidalized ones. (doi: 10.5562/cca2224

Mobility of Trace Elements in Pore Solutions of Portland Cement Pastes Exposed to Leaching

Two Portland cement pastes, CEM I 42.5R and CEM III/A 52.5N were exposed to leaching by soft water throughout a one–year hydration period. Mobility of trace elements was investigated by determination of their pore solution concentration in the course of time. Eleven trace elements were included in this research: antimony, arsenic, cadmium, chromium, cobalt, copper, mercury, nickel, lead, vanadium and zinc. The possible usage of the pore solution trace elements concentration in monitoring of deleterious leaching reactions and prediction of environmental risk was investigated. This work is licensed under a Creative Commons Attribution 4.0 International License

Structure of the T6 Human Nickel Insulin Derivative at 1.35 Å Resolution

This paper presents results of the structural investigation on the human insulin hexamer derivative stabilised by nickel coordination. Single crystals of the Ni-insulin derivative were prepared by the hanging drop vapour diffusion crystallisation method using metal-free insulin and nickel(II) acetate tetrahydrate. The low-temperature crystal structure was determined by the single crystal X-ray crystallographic method with data extending to 1.35 Å spacing. The investigated insulin derivative exhibits the T6 form of insulin and crystallizes in the trigonal system in space group R3, with the unit cell parameters a = b = 81.41 Å and c = 33.75 Å. There are two nickel atoms per insulin hexamer and both are octahedrally coordinated by three Nε2 atoms of three symmetry-related HisB10/HisD10 and three oxygen atoms of three symmetry-related water molecules