V4S9Br4: a novel high-spin vanadium cluster thiobromide with square-planar metal core

The novel vanadium thiobromide, V4S9Br4, with a square-planar metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic properties and the heat capacity, and DFT calculations of the electronic structure. At the room temperature, the compound displays paramagnetic properties with an independent spin on each V atom and with a weak exchange constant (J approximately 10 cm(-1)). The paramagnetic state is transformed into a low-spin state (AF-type ordering) at low temperatures. This change is accompanied by a heat-capacity anomaly. The observed magnetic and heat-capacity anomalies can be explained by the thermal excitation of electrons on the closely spaced molecular energy levels in the presence of the Jahn-Teller effect.     

Complexes of nickel(ii) and copper(ii) chlorides with a nitroxide radical derivative of 4-tetrazolyl-3-imidazolme-3-oxide

NiCl₂ and CuCl₂ complexes with a new stable nitroxyl radical, 2,2,5,5-tetramethyl-4-(tetrazol-5-yl)-3-imidazoline-3-oxide-1-oxyl (L), NiLCl₂· H₂O and CuLCl₂, have been synthesized. The _eff values attest to a weak exchange interaction between the paramagnetic centers in the temperature interval of 78–300 K.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 932–934, May, 1994.The authors are grateful to E. G. Boguslavskii for the registration and interpretation of the ESR spectrum, to V. A. Shipachev for the measurement of SDR, and to V. I. Lisoivan for the X-ray analysis.     

A Study of Antiferromagnetic Ordering in β-FeF3·3H2O by the Use of the NMR Method

The present work cites the investigation results of local magnetic fields on ¹H and ¹⁹F nuclei and spin ordering in β-FeF₃·3H₂O. In the structure of this compound (space group P4₂/n, a=7.846 Å, c=7.754 Å, z=4^1,2) Fe atoms are bonded via bridged F atoms (1) in infinite chains along the /001/ axis. With such positioning, in which two paramagnetic atoms are separated by a diamagnetic atom (F, O, C1 and others) there is a possibility for indirect (superexchange) interaction. Linear chains … Fe - F - Fe - F - Fe - F … are separated from each other by F(2) atoms and water molecules H₂O (1) and H₂O (2), so that exchange between neighboring Fe atoms from various chains is ostensibly much encumbered.     

Quantifying uncertainty in the measurement of arsenic in suspended particulate matter by Atomic Absorption Spectrometry with hydride generator

Arsenic is the toxic element, which creates several problems in human being specially when inhaled through air. So the accurate and precise measurement of arsenic in suspended particulate matter (SPM) is of prime importance as it gives information about the level of toxicity in the environment, and preventive measures could be taken in the effective areas. Quality assurance is equally important in the measurement of arsenic in SPM samples before making any decision. The quality and reliability of the data of such volatile elements depends upon the measurement of uncertainty of each step involved from sampling to analysis. The analytical results quantifying uncertainty gives a measure of the confidence level of the concerned laboratory. So the main objective of this study was to determine arsenic content in SPM samples with uncertainty budget and to find out various potential sources of uncertainty, which affects the results. Keeping these facts, we have selected seven diverse sites of Delhi (National Capital of India) for quantification of arsenic content in SPM samples with uncertainty budget following sampling by HVS to analysis by Atomic Absorption Spectrometer-Hydride Generator (AAS-HG). In the measurement of arsenic in SPM samples so many steps are involved from sampling to final result and we have considered various potential sources of uncertainties. The calculation of uncertainty is based on ISO/IEC17025: 2005 document and EURACHEM guideline. It has been found that the final results mostly depend on the uncertainty in measurement mainly due to repeatability, final volume prepared for analysis, weighing balance and sampling by HVS. After the analysis of data of seven diverse sites of Delhi, it has been concluded that during the period from 31^st Jan. 2008 to 7^th Feb. 2008 the arsenic concentration varies from 1.44 ± 0.25 to 5.58 ± 0.55 ng/m³ with 95% confidence level (k = 2).     

Structural characteristics of different types of nanoparticles synthesised in mesomorphic metal alkanoates

The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC₈) and of the cobalt octanoate (CoC₈). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained.     

Exchange parameters of five-spin clusters of Cu(II) coordination compounds with imidazoline nitroxide radicals

The exchange Heisenberg interaction parameters have been determined from theoretical analysis of the temperature dependence of magnetic susceptibility of coordination cluster compounds [Cu(hfacac)₂]₃(Li⁽ⁱ⁾)₂ (hfacac is hexafluoroacetylacetonate, L⁽ⁱ⁾ are 3-imidazoline nitroxides). Upon coordination of both N O oxygens and heterocycle N(3) atoms by Cu²⁺ ions, the interactions are ferromagnetic in nature and have the same order of magnitude. The minor intercluster interactions are antiferromagnetic.Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences. International Tomography Center. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 3, pp. 70–74, May–June 1993.Translated by L. Smolina