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Magnetic Susceptibility (magnetic + susceptibility)
Terms modified by Magnetic Susceptibility Selected AbstractsVariations in Chemical Composition of Clay Minerals and Magnetic Susceptibility of Hydrothermally Altered Rocks in the Hishikari Epithermal Gold Deposit, SW Kyushu, JapanRESOURCE GEOLOGY, Issue 1 2008Hiroyasu Murakami Abstract Hydrothermal alteration, involving chiefly chlorite and illite, is extensively distributed within host rocks of the Pleistocene Hishikari Lower Andesites (HLA) and the Cretaceous Shimanto Supergroup (SSG) in the underground mining area of the Hishikari epithermal gold deposit, Kagoshima, Japan. Approximately 60% of the mineable auriferous quartz-adularia veins in the Honko vein system occur in sedimentary rocks of the SSG, whereas all the veins of the Yamada vein system occur in volcanic rocks of the HLA. Variations in the abundance and chemical composition of hydrothermal minerals and magnetic susceptibility of the hydrothermally altered rocks of the HLA and SSG were analyzed. In volcanic rocks of the HLA, hydrothermal minerals such as quartz, chlorite, adularia, illite, and pyrite replaced primary minerals. The amount of hydrothermal minerals in the volcanic rocks including chlorite, adularia, illite, and pyrite as well as the altered and/or replaced pyroxenes and plagioclase phenocrysts increases toward the veins in the Honko vein system. The vein-centered variation in mineral assemblage is pronounced within up to 25 m from the veins in the peripheral area of the Honko vein system, whereas it is not as apparent in the Yamada vein system. The hydrothermal minerals in sandstone of the SSG occur mainly as seams less than a few millimeters thick and are sporadically observed in halos along the veins and/or the seams. The alteration halos in sandstone of the SSG are restricted to within 1 m of the veins. In the peripheral area of the Honko vein system, chlorite in volcanic rocks is characterized by increasing in Al in its tetrahedral layer and the Fe/Fe + Mg ratio toward the veins, while illite in volcanic rocks has relatively low K and a restricted range of Fe/Fe + Mg ratios. Temperature estimates derived from chlorite geothermometry rise toward the veins within the volcanic rocks. The magnetic susceptibility of tuff breccia of the HLA varies from 21 to less than 0.01 × 10,3 SI within a span of 40 m from the veins and has significant variation relative to that of andesite (27,0.06 × 10,3 SI). The variation peripheral to the Honko vein system correlates with an increase in the abundance of hematite pseudomorphs after magnetite, the percentage of adularia and chlorite with high Fe/Fe + Mg ratios, and the degree of plagioclase alteration with decreasing distance to the veins. In contrast, sedimentary rocks of the SSG maintain a consistent magnetic susceptibility across the alteration zone, within a narrow range from 0.3 to 0.2 × 10,3 SI. Magnetic susceptibility of volcanic rocks of the HLA, especially tuff breccia, could serve as an effective exploration tool for identifying altered volcanic rocks. [source] Granitoids and Their Magnetic Susceptibility in South KoreaRESOURCE GEOLOGY, Issue 3 2001Myung, Shik JIN Abstract: Magnetic susceptibility (MS) measurements were carried out for 1,120 samples in the Middle Proterozoic to Early Tertiary granitoids so far recognized in South Korea, and the lateral and spatial variation of their magnetic susceptibility, i.e., content of magnetite, is studied. The Middle Proterozoic two mica granitoids related to cassiterite (Sn) deposits in northeastern part of the Sobaegsan Massif show very low MS (less than 0.3 A- 10 -3 SI unit), and the Permo-Triassic tonalitic to granodioritic and monzonitic rocks which are barren in mineralization, distributed in the middle part of South Korea also show low MS (less than 1 A- 10 -3 SI unit). On the contrary the Late Triassic to Jurassic granitoids (= Daebo granitoids) which were evolved from tonalite through granodiorite to granite, and are most widely distributed in South Korea, show a wide variation on MS. Particularly in the Andong, Igsan, Gimcheon and Geochang areas, the granitoids which are barren in mineralization, are characterized by high MS (more than 10 A- 10 -3 SI unit). The Chuncheon, Jecheon, Namyang and Geumsan plutons related to molybdenite (Mo) and/or wolframite or scheelite (W), and fluorite (F) mineralizations show a little high MS (more than 3 A- 10 -3 SI unit). However, more than 60% of the Daebo granitoids show low MS (less than 3 A- 10 -3 SI unit) and the rest show a little high MS (more than 3 A- 10 -3 SI unit). Heterogeneous distribution of magnetite content in the Daebo granitoids is considered to reflect heterogeneity of redox state of the source materials for these granitoids. The Cretaceous to Early Tertiary granitoids (= Bulgugsa granitoids) in the Gyeongsang Basin had been generally evolved in the order of tonalite, diorite, granodiorite, granite and alkali-feldspar granites, which are closely related to base metal ore deposits, and mostly show higher MS (more than 3 A- 10 -3 SI unit) than other granitoids mentioned above, although some exceptions are recognized in highly evolved alkali-feldspar granites (SiO2 > 76%). In contrast, as most of the highly oxidized or evolved Cretaceous granitoids distributed in areas other than the Gyeongsang Basin show lower MS than those of the Gyeongsang Basin, and appear to be magnetite free, ilmenite-series granites, but they might be hematite bearing magnetite-series granitoids. Highly oxidized nature of the Bulgugsa granitoids may be due to high Fe2O3/FeO ratio of the source materials and also high level intrusion style of the granitic magma activities. Most of the granitic rocks of the Middle Proterozoic, Permo-Triassic and more than 60% of the Late Triassic to Jurassic (Daebo granitoids) belong to ilmenite,series, however less than 40% of the Daebo granitoids and most Cretaceous ones are magnetite,series. Thus, the granitic magma intruded in Korean Peninsula became oxidized while the intrusive ages become younger. [source] The Construction Process of the Angkor Monuments Elucidated by the Magnetic Susceptibility of Sandstone,ARCHAEOMETRY, Issue 2 2003E. Uchida The Angkor monuments in Cambodia are mainly constructed of grey to yellowish-brown sandstones. No differences in the constituent minerals and in the chemical composition of the sandstones have been confirmed among the monuments. However, we have found their magnetic susceptibility a useful parameter by which to distinguish them. The principal monuments of Angkor Wat, Ta Prohm, Preah Khan, Banteay Kdei and Bayon, constructed from the Angkor Wat period to the Bayon period (from the beginning of the 12th century to the beginning of the 13th century ad), were investigated in detail using a portable magnetic susceptibility meter. We succeeded in dividing the periods of construction into stages. This elucidated the enlargement process of the monuments and correlated their construction stages. [source] Magnetic susceptibility: Further insights into macroscopic and microscopic fields and the sphere of LorentzCONCEPTS IN MAGNETIC RESONANCE, Issue 1 2003C.J. Durrant Abstract To make certain quantitative interpretations of spectra from NMR experiments carried out on heterogeneous samples, such as cells and tissues, we must be able to estimate the magnetic and electric fields experienced by the resonant nuclei of atoms in the sample. Here, we analyze the relationships between these fields and the fields obtained by solving the Maxwell equations that describe the bulk properties of the materials present. This analysis separates the contribution to these fields of the molecule in which the atom in question is bonded, the "host" fields, from the contribution of all the other molecules in the system, the "external" fields. We discuss the circumstances under which the latter can be found by determining the macroscopic fields in the sample and then removing the averaged contribution of the host molecule. We demonstrate that the results produced by the, so-called, "sphere of Lorentz" construction are of general validity in both static and time-varying cases. This analytic construct, however, is not "mystical" and its justification rests not on any sphericity in the system but on the local uniformity and isotropy, i.e., spherical symmetry, of the medium when averaged over random microscopic configurations. This local averaging is precisely that which defines the equations that describe the macroscopic fields. Hence, the external microscopic fields, in a suitably averaged sense, can be estimated from the macroscopic fields. We then discuss the calculation of the external fields and that of the resonant nucleus in NMR experiments. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson Part A 18A: 72,95, 2003 [source] Crystal growth and magnetic properties of the copper coordination polymer [Cu(µ -C2O4)(4-aminopyridine)2(H2O)]nCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2007A. V. Prokofiev Abstract In this paper, we consider various ways of crystal growth of the polymer [Cu(µ -C2O4)(4-aminopyridine)2(H2O)]n. Single crystals of the size of 1.5×1.5×0.2 mm3 have been grown by a slow diffusion technique from solutions of the monoammine copper complex and of the mixture of potassium oxalate and aminopyridine with the stoichiometric ratio. Magnetic susceptibility and ESR measurements have been performed on single crystals large enough for investigating anisotropic properties. The susceptibility can be well described within the model of a Heisenberg antiferromagnetic spin chain. The magnetic measurements reveal a small concentration of paramagnetic moments reflecting the high quality of the single crystals. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Textural and compositional controls on modern beach and dune sands, New ZealandEARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2007J. J. Kasper-Zubillaga Abstract Textural, compositional, physical and geophysical determinations were carried out on 111 beach and dune sand samples from two areas in New Zealand: the Kapiti,Foxton coast sourced by terranes of andesite and greywackes and the Farewell Spit,Wharariki coast sourced by a wide variety of Paleozoic terranes. Our aim is to understand how long-shore drift, beach width and source rock control the sedimentological and petrographic characteristics of beach and dune sands. Furthermore, this study shows the usefulness of specific minerals (quartz, plagioclase with magnetite inclusions, monomineralic opaque grains) to interpret the physical processes (fluvial discharges, long-shore currents, winds) that distribute beach and dune sands in narrow and wide coastal plains. This was done by means of direct (grain size and modal analyses) and indirect (specific gravity, magnetic/non-magnetic separations M/NM, magnetic susceptibility measurements, hysteresis loops) methods. Results are compared with beach sands from Hawaii, Oregon, the Spanish Mediterranean, Elba Island and Southern California. Compositionally, the Kapiti,Foxton sands are similar to first-order immature sands, which retain their fluvial signature. This results from the high discharge of rivers and the narrow beaches that control the composition of the Kapiti,Foxton sands. The abundance of feldspar with magnetite inclusions controls the specific gravity of the Kapiti,Foxton sands due to their low content of opaque minerals and coarse grain size. Magnetic susceptibility of the sands is related mainly to the abundance of feldspars with Fe oxides, volcanic lithics and free-opaque minerals. The Farewell Spit,Wharariki sands are slightly more mature than the Kapiti,Foxton sands. The composition of the Farewell Spit,Wharariki sands does not reflect accurately their provenance due to the prevalence of long-shore drift, waves, little river input and a wide beach. Low abundance of feldspar with magnetite inclusions and free opaque grains produces poor correlations between specific gravity (Sg) and Fe oxide bearing minerals. The small correlation between opaque grains and M/NM may be related to grain size. The magnetic susceptibility of Farewell Spit,Wharariki sands is low due to the low content of grains with magnetite inclusions. Hysteresis and isothermal remnant magnetization (IRM) agree with the magnetic susceptibility values. Copyright © 2006 John Wiley & Sons, Ltd. [source] A New Trinuclear Linear Copper(II) Complex: Unusual Crystal Structure with Semi-Coordinated Thiophene Moieties and Weak Antiferromagnetic Coupling Through the Bridging Imidazolate RingsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2004Yufei F. Song Abstract A trinuclear copper(II) complex, [Cu3(imthio)2(NO3)4(MeOH)2] [where Himthio is 1,1-bis(imidazol-2-yl)-3-(thiophen-2-yl)-2-azapropane], has been synthesized by the reaction of Himthio with Cu(NO3)2·3H2O in MeOH. The structure of the copper complex is centrosymmetric and contains a linear trinuclear array of copper atoms. The central copper(II) ion, Cu1, which lies on an inversion centre, is equatorially coordinated by four nitrogen atoms from two anionic imthio ligands and axially by two semicoordinated thiophene sulfur atoms to give an octahedral environment (Cu1,S1 3.136 Å). The Himthio ligand bridges Cu1 and the terminal copper(II) ions through imidazole nitrogen atoms. The coordination around the external ions is completed by the oxygen atoms from two nitrate groups and by a methanol molecule in a distorted square-pyramidal geometry. The two terminal copper(II) complexes can be considered to be chelating ligands for the central CuII ion. The EPR spectrum of the complex in MeOH at 77 K shows two mononuclear species, as is fully confirmed by EPR simulation. Magnetic susceptibility of the complex shows weak antiferromagnetic behaviour (J = ,71.37 cm,1) caused by the overlapping of the magnetic orbitals of the copper atoms and the bridging imidazolate rings. (© Wiley-VCH Verlag GmbH & Co.. KGaA, 69451 Weinheim, Germany, 2004) [source] Sensitivity of multi-coil frequency domain electromagnetic induction sensors to map soil magnetic susceptibilityEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2010D. Simpson Magnetic susceptibility is an important indicator of anthropogenic disturbance in the natural soil. This property is often mapped with magnetic gradiometers in archaeological prospection studies. It is also detected with frequency domain electromagnetic induction (FDEM) sensors, which have the advantage that they can simultaneously measure the electrical conductivity. The detection level of FDEM sensors for magnetic structures is very dependent on the coil configuration. Apart from theoretical modelling studies, a thorough investigation with field models has not been conducted until now. Therefore, the goal of this study was to test multiple coil configurations on a test field with naturally enhanced magnetic susceptibility in the topsoil and with different types of structures mimicking real archaeological features. Two FDEM sensors were used with coil separations between 0.5 and 2 m and with three coil orientations. First, a vertical sounding was conducted over the undisturbed soil to test the validity of a theoretical layered model, which can be used to infer the depth sensitivity of the coil configurations. The modelled sounding values corresponded well with the measured data, which means that the theoretical models are applicable to layered soils. Second, magnetic structures were buried in the site and the resulting anomalies measured to a very high resolution. The results showed remarkable differences in amplitude and complexity between the responses of the coil configurations. The 2-m horizontal coplanar and 1.1-m perpendicular coil configurations produced the clearest anomalies and resembled best a gradiometer measurement. [source] Integration of magnetism and heavy metal chemistry of soils to quantify the environmental pollution in Kathmandu, NepalISLAND ARC, Issue 4 2005Pitambar Gautam Abstract Soil profiles of the Kathmandu urban area exhibit significant variations in magnetic susceptibility (,) and saturation isothermal remanence (SIRM), which can be used to discriminate environmental pollution. Magnetic susceptibility can be used to delineate soil intervals by depth into normal (< 10,7 m3/kg), moderately enhanced (10,7,< 10,6 m3/kg) and highly enhanced (, 10,6 m3/kg). Soils far from roads and industrial sites commonly fall into the ,normal' category. Close to a road corridor, soils at depths of several centimeters have the highest ,, which remains high within the upper 20 cm interval, and decreases with depth through ,moderately magnetic' to ,normal' at approximately 30,40 cm. Soils in the upper parts of profiles in urban recreational parks have moderate ,. Soil SIRM has three components of distinct median acquisition fields (B1/2): soft (30,50 mT, magnetite-like phase), intermediate (120,180 mT, probably maghemite or soft coercivity hematite) and hard (550,600 mT, hematite). Close to the daylight surface, SIRM is dominated by a soft component, implying that urban pollution results in enrichment by a magnetite-like phase. Atomic absorption spectrometry of soils from several profiles for heavy metals reveals remarkable variability (ratio of maximum to minimum contents) of Cu (16.3), Zn (14.8) and Pb (9.3). At Rani Pokhari, several metals are well correlated with ,, as shown by a linear relationship between the logarithmic values. At Ratna Park, however, both , and SIRM show significant positive correlation with Zn, Pb and Cu, but poor and even negative correlation with Fe (Mn), Cr, Ni and Co. Such differences result from a variety of geogenic, pedogenic, biogenic and man-made factors, which vary in time and space. Nevertheless, for soil profiles affected by pollution (basically traffic-related), , exhibits a significant linear relationship with a pollution index based on the contents of some urban elements (Cu, Pb, Zn), and therefore it serves as an effective parameter for quantifying the urban pollution. [source] Yellow-brown earth on Quaternary red clay in Langxi County, Anhui Province in subtropical China: Evidence for paleoclimatic change in late Quaternary period,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2008Xue-Feng Hu Abstract In order to investigate the paleoclimatic changes in S China during the late Quaternary and their influence on pedogenesis and soil classification, a yellow-brown earth (YBE),red clay (RC) profile in Langxi County, Anhui Province was studied. The grain-size distribution and the major- and trace-element compositions of the profile indicate that the YBE of the profile shares the same origin with the YBE in Jiujiang and Xuancheng and the Xiashu loess in Zhenjiang, and the underlying RC also has aeolian characteristics and shares the same origin with the Xiashu loess. Grain-size characteristics, molecular ratios of SiO2/Al2O3, SiO2/(Al2O3+Fe2O3), and BA ([CaO+MgO+K2O+Na2O]/Al2O3) and other weathering indices (CaO/TiO2, MgO/TiO2, K2O/TiO2, Na2O/TiO2, and Rb/Sr) of the profile indicate that the RC is more strongly weathered than the YBE. Magnetic susceptibility (,lf) of the uniform red clay (URC) of the profile is significantly enhanced. However, that of the underlying reticulate red clay (RRC) is significantly decreased because of the paleogroundwater movement and cannot indicate its strong weathering properties. The YBE-RC profile in Langxi County recorded a great climatic change during late Quaternary: At that time, the pedogenic development of the RC was terminated and widespread dust deposition occurred. The parent material of the RC may be aeolian deposits which were accumulated before the last interglacial and were strongly weathered and rubified under the subsequent interglacial climate. It is observed that red soils, derived from the RC, and yellow-brown soils, derived from the YBE, coexist in the study area, which is contradictive to the theory of the zonal distribution of soils. Therefore, it is necessary to take into account the history of Quaternary climatic changes when studying pedogenesis. [source] Variations in Chemical Composition of Clay Minerals and Magnetic Susceptibility of Hydrothermally Altered Rocks in the Hishikari Epithermal Gold Deposit, SW Kyushu, JapanRESOURCE GEOLOGY, Issue 1 2008Hiroyasu Murakami Abstract Hydrothermal alteration, involving chiefly chlorite and illite, is extensively distributed within host rocks of the Pleistocene Hishikari Lower Andesites (HLA) and the Cretaceous Shimanto Supergroup (SSG) in the underground mining area of the Hishikari epithermal gold deposit, Kagoshima, Japan. Approximately 60% of the mineable auriferous quartz-adularia veins in the Honko vein system occur in sedimentary rocks of the SSG, whereas all the veins of the Yamada vein system occur in volcanic rocks of the HLA. Variations in the abundance and chemical composition of hydrothermal minerals and magnetic susceptibility of the hydrothermally altered rocks of the HLA and SSG were analyzed. In volcanic rocks of the HLA, hydrothermal minerals such as quartz, chlorite, adularia, illite, and pyrite replaced primary minerals. The amount of hydrothermal minerals in the volcanic rocks including chlorite, adularia, illite, and pyrite as well as the altered and/or replaced pyroxenes and plagioclase phenocrysts increases toward the veins in the Honko vein system. The vein-centered variation in mineral assemblage is pronounced within up to 25 m from the veins in the peripheral area of the Honko vein system, whereas it is not as apparent in the Yamada vein system. The hydrothermal minerals in sandstone of the SSG occur mainly as seams less than a few millimeters thick and are sporadically observed in halos along the veins and/or the seams. The alteration halos in sandstone of the SSG are restricted to within 1 m of the veins. In the peripheral area of the Honko vein system, chlorite in volcanic rocks is characterized by increasing in Al in its tetrahedral layer and the Fe/Fe + Mg ratio toward the veins, while illite in volcanic rocks has relatively low K and a restricted range of Fe/Fe + Mg ratios. Temperature estimates derived from chlorite geothermometry rise toward the veins within the volcanic rocks. The magnetic susceptibility of tuff breccia of the HLA varies from 21 to less than 0.01 × 10,3 SI within a span of 40 m from the veins and has significant variation relative to that of andesite (27,0.06 × 10,3 SI). The variation peripheral to the Honko vein system correlates with an increase in the abundance of hematite pseudomorphs after magnetite, the percentage of adularia and chlorite with high Fe/Fe + Mg ratios, and the degree of plagioclase alteration with decreasing distance to the veins. In contrast, sedimentary rocks of the SSG maintain a consistent magnetic susceptibility across the alteration zone, within a narrow range from 0.3 to 0.2 × 10,3 SI. Magnetic susceptibility of volcanic rocks of the HLA, especially tuff breccia, could serve as an effective exploration tool for identifying altered volcanic rocks. [source] Granitoids and Their Magnetic Susceptibility in South KoreaRESOURCE GEOLOGY, Issue 3 2001Myung, Shik JIN Abstract: Magnetic susceptibility (MS) measurements were carried out for 1,120 samples in the Middle Proterozoic to Early Tertiary granitoids so far recognized in South Korea, and the lateral and spatial variation of their magnetic susceptibility, i.e., content of magnetite, is studied. The Middle Proterozoic two mica granitoids related to cassiterite (Sn) deposits in northeastern part of the Sobaegsan Massif show very low MS (less than 0.3 A- 10 -3 SI unit), and the Permo-Triassic tonalitic to granodioritic and monzonitic rocks which are barren in mineralization, distributed in the middle part of South Korea also show low MS (less than 1 A- 10 -3 SI unit). On the contrary the Late Triassic to Jurassic granitoids (= Daebo granitoids) which were evolved from tonalite through granodiorite to granite, and are most widely distributed in South Korea, show a wide variation on MS. Particularly in the Andong, Igsan, Gimcheon and Geochang areas, the granitoids which are barren in mineralization, are characterized by high MS (more than 10 A- 10 -3 SI unit). The Chuncheon, Jecheon, Namyang and Geumsan plutons related to molybdenite (Mo) and/or wolframite or scheelite (W), and fluorite (F) mineralizations show a little high MS (more than 3 A- 10 -3 SI unit). However, more than 60% of the Daebo granitoids show low MS (less than 3 A- 10 -3 SI unit) and the rest show a little high MS (more than 3 A- 10 -3 SI unit). Heterogeneous distribution of magnetite content in the Daebo granitoids is considered to reflect heterogeneity of redox state of the source materials for these granitoids. The Cretaceous to Early Tertiary granitoids (= Bulgugsa granitoids) in the Gyeongsang Basin had been generally evolved in the order of tonalite, diorite, granodiorite, granite and alkali-feldspar granites, which are closely related to base metal ore deposits, and mostly show higher MS (more than 3 A- 10 -3 SI unit) than other granitoids mentioned above, although some exceptions are recognized in highly evolved alkali-feldspar granites (SiO2 > 76%). In contrast, as most of the highly oxidized or evolved Cretaceous granitoids distributed in areas other than the Gyeongsang Basin show lower MS than those of the Gyeongsang Basin, and appear to be magnetite free, ilmenite-series granites, but they might be hematite bearing magnetite-series granitoids. Highly oxidized nature of the Bulgugsa granitoids may be due to high Fe2O3/FeO ratio of the source materials and also high level intrusion style of the granitic magma activities. Most of the granitic rocks of the Middle Proterozoic, Permo-Triassic and more than 60% of the Late Triassic to Jurassic (Daebo granitoids) belong to ilmenite,series, however less than 40% of the Daebo granitoids and most Cretaceous ones are magnetite,series. Thus, the granitic magma intruded in Korean Peninsula became oxidized while the intrusive ages become younger. [source] ,-Ca3N2, a Metastable Nitride in the System Ca,NCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2009Peter Höhn Dr. Abstract A new page in the phase book: The metastable nitride ,-Ca3N2, the synthesis, crystal structure (see picture), and physical properties of which are reported, is an isotype of corundum (,-Al2O3). Vacancies in the crystal structure of ,-Ca3N2 are discussed by using full-potential local orbital methods and taking into account both the physical properties and the density of states. The structural chemistry of calcium nitrides is represented by just two different intermediate phases: cubic Ca3N2 (referred to as ,-Ca3N2, Mn2O3 type structure) and Ca2N (CdCl2 type structure). Other binary phases (",-Ca3N2", "Ca11N8") have been proven to represent cyanamide nitrides, Ca4N2[CN2] and Ca11N6[CN2]2, respectively. The metastable nitride ,-Ca3N2 is prepared either by reaction of freshly distilled calcium metal with nitrogen at 700,K, or by reaction of Ca2N with N2 at 500,K. ,-Ca3N2 transforms monotropically (Ttrans,810,K) to cubic ,-Ca3N2. The crystal structure of ,-Ca3N2 (rhombohedral Rc, no. 167, a=619.884(3),pm, c=1662.958(10),pm) is an isotype of the corundum structure (,-Al2O3) and comprises a network of NCa6/4 octahedra that share common faces and edges. Magnetic susceptibility and electrical resistivity measurements confirm that ,-Ca3N2 is a diamagnetic semiconductor. Die Strukturchemie der Calciumnitride wird von lediglich zwei intermediären Verbindungen bestimmt: kubisches Ca3N2 (nachfolgend als , -Ca3N2 bezeichnet; Mn2O3 -Strukturtyp) und das im CdCl2 -Strukturtyp kristallisierende Ca2N. Die binären Phasen ,, -Ca3N2" und ,Ca11N8" konnten inzwischen als die Cyanamid-Nitride Ca4N2[CN2] und Ca11N6[CN2]2 identifiziert werden. Metastabiles , -Ca3N2 kann entweder durch Reaktion von frisch destilliertem Calcium-Metall mit Stickstoff bei 700,K oder durch Umsetzung von Ca2N mit N2 bei 500,K erhalten werden. , -Ca3N2 transformiert monotrop (Ttrans,810,K) zur kubischen Phase , -Ca3N2. Die Kristallstruktur von , -Ca3N2 (rhomboedrisch Rc, No. 167, a=619.884(3),pm, c=1662.958(3),pm) ist isotyp zur Korundstruktur (, -Al2O3) und besteht aus einem Netzwerk von NCa6/4 -Oktaedern, die über gemeinsame Flächen und Kanten verknüpft sind. Messungen der magnetischen Suszeptibilität und des elektrischen Widerstands zeigen, daß , -Ca3N2 ein diamagnetischer Halbleiter ist. [source] Syntheses, Structures and Magnetic Properties of Trinuclear CuIIMIICuII (M = Cu, Ni, Co and Fe) and Tetranuclear [2×1+1×2] CuIIMnII,2CuII Complexes Derived from a Compartmental Ligand: The Schiff Base 3-Methoxysalicylaldehyde Diamine Can also Stabilize a CocrystalEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2010Arpita Biswas Abstract The present investigation describes syntheses, characterization and studies of the mononuclear compound [CuIIL,(H2O)] (1), the triangular, trinuclear monophenoxido-bridged compounds [{CuIIL}2MII(H2O)2](ClO4)2·nH2O [2 (M = Cu, n = 0), 3 (M = Ni, n = 3), 4 (M = Co, n = 0), 5 (M = Fe, n = 0)] and the tetrametallic self-assembled complex [{CuIILMnII(H2O)3}{CuIIL}2](ClO4)2·H2O (6) derived from compartmental Schiff base ligand, H2L, which is the [2+1] condensation product of 3-methoxysalicylaldehyde and trans -1,2-diaminocyclohexane. Single-crystal X-ray structures of 2, 5 and 6 were determined. Two pairs of terminal···central metal ions in the trinuclear cores in 2 and 5 are monophenoxido-bridged. Interestingly, the CuO6 and FeO6 environments have tetragonally compressed octahedral geometries. On the other hand, the structure of 6 reveals that it is a [2×1+1×2] cocrystal of one diphenoxido-bridged dinuclear [CuIILMnII(H2O)3]2+ dication and two mononuclear [CuIIL] moieties. Cocrystallization in 6 takes place as a result of water encapsulation. The variable-temperature (2,300 K) magnetic susceptibilities of compounds 2,6 have been measured. The exchange integrals obtained are: the CuII3 compound 2, J = ,78.9 cm,1; the CuIINiIICuII compound 3, J = ,22.8 cm,1; the CuIICoIICuII compound 4, J = ,7.8 cm,1; the CuIIFeIICuII compound 5, J = ,3.0 cm,1; the CuII3MnII compound 6, J = ,15.1 cm,1. The monophenoxido-bridging core in 3 and 4 has been proposed after comparison of the structures and magnetic properties of these two compounds with those of 2, 5 and related other compounds. This paper presents rare examples of monophenoxido-bridged CuIIMIICuII (M = Cu, Ni, Co and Fe) compounds, provides an understanding of the structures from magnetic exchange integrals, and, most importantly, reports on the first example of a cocrystal derived from a 3-methoxysalicylaldehyde diamine compartmental ligand. [source] Magnetic and Electrochemical Properties of a Heterobridged ,-Phenoxido,,1,1 -Azide Dinickel(II) Compound: A Unique Example Demonstrating the Bridge Distance Dependency of Exchange IntegralEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2009Rajesh Koner Abstract The synthesis, structure, magnetic and electrochemical properties of the heterobridged ,-phenoxido,,1,1 -azide dinickel(II) compound [NiII2(HL1)3(,1,1 -N3)]·3H2O (1) derived from the tetradentate Schiff base ligand N -(2-hydroxyethyl)-3-methoxysalicylaldimine (H2L1) are described. The title compound crystallizes in the triclinic system (space group P). Electrochemical analyses reveal that compound 1 exhibits two-step quasireversible couples in the reduction window with E1/2 values of ,1412 and ,1762 mV. The variable-temperature (2,300 K) magnetic susceptibilities at 1 T of the title compound were measured. The interaction between the metal centres is weak ferromagnetic (J = 5.0 cm,1, g = 2.23, D1 = 29.2 cm,1 and D2 = 10.7 cm,1). Comparison of the exchange integral of 1 with that of the only reported ,-phenoxido,,1,1 -azide dinickel(II) compound results in the emergence of a unique example of the dependence of strength of magnetic exchange interaction on the metal,ligand bridge distance. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] One-Dimensional Coordination Polymers of MnII, CuII, and ZnII Supported by Carboxylate-Appended (2-Pyridyl)alkylamine Ligands , Structure and MagnetismEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2009Himanshu Arora Abstract Four new complexes [MnII(L1OO)(H2O)][ClO4]·2H2O (1), [ZnII(L1OO)][ClO4]·2H2O (2), [CuII(L3OO)][CF3SO3]·H2O (3), and [ZnII(L3OO)][ClO4] (4) (L1OO, = 3-[(2-(pyridine-2-yl)ethyl){2-(pyridine-2-yl)methyl}amino]propionate; L3OO, = 3-[(2-(pyridine-2-yl)ethyl){(dimethylamino)ethyl}amino]propionate) have been synthesized and characterized by elemental analysis, IR, and UV/Vis spectroscopy. Structural analysis revealed that 1, 3, and 4 are one-dimensional chain-like coordination polymers. In 1 distorted octahedral MnN3O3 and in 3 square-pyramidal CuN3O2 coordination is satisfied by three nitrogen atoms and an appended carboxylate oxygen atom of the ligand, and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 4 trigonal bipyramidal ZnN3O2 coordination environment is provided by two nitrogen atoms and an appended carboxylate oxygen atom of the ligand in the equatorial plane, and the two axial positions are satisfied by a tertiary amine nitrogen and an oxygen atom belonging to the carboxylate group of an adjacent molecule. In 1 the MnII center is coordinated by an additional water molecule. In these complexes each monomeric unit is sequentially connected by syn - anti carboxylate bridges. Temperature-dependent magnetic susceptibilities for 1 and 3 are measured, revealing antiferromagnetic interactions through syn - anti carboxylate bridges between the MII centers. Analysis of the crystal packing diagram reveals that in 1 extensive ,,, stacking involving alternate pyridine rings of adjacent 1D chain exists, which eventually lead to the formation of a 2D network structure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] UV-vis-Induced Vitrification of a Molecular Crystal,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2007T. Naito Abstract A charge-transfer complex of 2,5-dimethyl- N,N,-dicyanoquinonediimine (DM) with silver (crystalline Ag(DM)2, defined as ,) is irreversibly transformed by UV-vis illumination. Depending on the illumination conditions, three new types of solids (defined as ,, ,, and ,) with different structural and physical properties are obtained and examined by a variety of analytical techniques, including solid-state, high-resolution, cross-polarization magic angle spinning (CP-MAS) 13C,NMR, elemental analysis (EA), mass spectrometry (MS), X-ray absorption fine structure (XAFS), and powder X-ray diffraction (XRD). The CP-MAS, EA, MS, and XAFS results indicate that compound , is a glass state of Ag(DM)2. The transformation from crystalline (,) to amorphous (,) solid Ag(DM)2 is an irreversible exothermic glass transition (glass-transition temperature 155.2,°C; ,H,=,,126.8,kJ,mol,1), which implies that the glass form is thermodynamically more stable than the crystalline form. Compound , (Ag(DM)1.5) consists of silver nanoparticles (diameter (7,±,2),nm ) dispersed in a glassy matrix of neutral DM molecules. The N,CN,Ag coordination bonds of the , form are not maintained in the , form. Decomposition of , by intense illumination results in a white solid (,), identified as being composed of silver nanoparticles (diameter (60,±,10),nm). Physical and spectroscopic (XAFS) measurements, together with XRD analysis, indicate that the silver nanoparticles in both , and , are crystalline with lattice parameters similar to bulk silver; however, the magnetic susceptibilities differ from bulk silver. [source] Thermal, catalytic, antimicrobial, and chelating aspects of phenolic resin and its polychelates with f-block elementsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008M. M. Patel Abstract The polymeric ligand (resin) was synthesized by condensation of 2-hydroxy-4-ethoxybenzophenone with ethane diol in the presence of polyphosphoric acid as a catalyst at 145°C for 10 h. The synthesized resin was used to study its ion exchange efficiency and to synthesize its polychelates with 4f-block elements. The resin and its polychelates were characterized on the basis of elemental analyses, electronic spectra, magnetic susceptibilities, IR, NMR, and thermogravimetric analyses. The molecular weight was determined using number,average molecular weight (Mn) by a vapor pressure osmometry (VPO) method. Ion-exchange studies at various concentrations of different electrolytes, pH, and rate have been carried out for f-block elements. Antimicrobial activity of all polychelates and catalytic activity of selected polychelates in organic synthesis have been studied. It is observed that resin can be used as an ion-exchanger and polychelates are found to be an efficient catalysts and antimicrobial agents. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] The influence of waterlogging and variations in pedology and ignition upon resultant susceptibilities: a series of laboratory reconstructionsARCHAEOLOGICAL PROSPECTION, Issue 2 2004D. G. Weston Abstract Magnetic survey techniques, such as fluxgate gradiometry, depend greatly on bodies of soil developing enhanced magnetic susceptibilities. Coarse mineral soils, especially those subject to a high groundwater table, often fail to develop enhanced susceptibilities and gradiometry. An example of this is Easingwold, in the Vale of York, UK. Gradiometry detected very little, however, subsequent excavation uncovered a complex of features suggesting multiphase activity and evidence for industry. This non-detection is attributed to the coarse mineral soils and the high watertable. Several laboratory reconstructions were made to investigate the influence of specific characteristics of soil and ignition episode upon susceptibility. It was found that variations in soil texture had marked impacts on the levels of susceptibility attained, as did waterlogging. Leaching had a limited effect upon soil magnetic susceptibility, but there was variation according to texture. Copyright © 2004 John Wiley & Sons, Ltd. [source] Cyano-bridged Ln3+ -Cr3+ Binuclear Complexes [Ln(L)x(H2O)yCr(CN)6]·mL·nH2O (Ln=La,Nd, x=5, y=2, m=1 or 2, n=2 or 2.5; Ln=Sm,Dy, Er, x=4, y=3, m=0, n=1.5 or 2.0; L=2-pyrrolidinone): Structure, Magnetism and Spin Density MapCHINESE JOURNAL OF CHEMISTRY, Issue 3 2007Xian-Ru Sun Abstract In order to shed light upon the nature and mechanism of 4f-3d magnetic exchange interactions, a series of binuclear complexes of lanthanide(3+) and chromium(3+) with the general formula [Ln(L)5(H2O)2Cr(CN)6]·mL·nH2O (Ln=La (1), Ce (2), Pr (3), Nd (4); x=5, y=2, m=1 or 2, n=2 or 2.5; L=2-pyrrolidinone) and [Ln(L)4(H2O)3Cr(CN)6] ·nH2O (Ln=Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Er (10); x=4, y=3, m=0, n=1.5 or 2.0; L2-pyrrolidinone) were prepared and the X-ray crystal structures of complexes 2, 6 and 7 were determined. All the compounds consist of a Ln-CN-Cr unit, in which Ln3+ in a square antiprism environment is bridged to an octahedral coordinated Cr3+ ion through a cyano group. The magnetic properties of the complexes 3 and 6,10 show an overall antiferromagnetic behavior. The fitting to the experimental magnetic susceptibilities of 7 give g=1.98, J=0.40 cm,1, zJ,=,0.21 cm,1 on the basis of a binuclear spin system (SGd=7/2, SCr=3/2), revealing an intra-molecular Gd3+ -Cr3+ ferromagnetic interaction and an inter-molecular antiferromagnetic interaction. For 7 the calculation of quantum chemical density functional theory (DFT), combined with the broken symmetry approach, showed that the calculated spin coupling constant was 20.3 cm,1, supporting the observation of weak ferromagnetic intra-molecular interaction in 7. The spin density distributions of 7 in both the high spin ground state and the broken symmetry state were obtained, and the spin coupling mechanism between Gd3+ and Cr3+ was discussed. [source] Preparation and characterization of powders and crystals of Vn-xTixO2n-1 Magneli oxidesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005D. Calestani Abstract Vn-xTixO2n-1 Magnéli phases have been synthesized under vacuum in powder form (n = 4, 0 , x , 0.4) and crystals (n = 4 and 5, x = 0.5 and 1.4, respectively), grown by chemical vapour transport in closed ampoules. TeCl4 and NH4Cl were used as transporting agents. Needle-shaped crystals as long as 200-300 micrometers or 2-3 mm were obtained when in presence of NH4Cl or TeCl4, respectively. The powder and crystal structures were examined by X-ray diffraction and the transport and magnetic characteristics were measured.. The powders resulted to be single-phase and the relevant composition was assumed to be equal to the nominal one. The overall stoichiometry of compounds, n, was determined from single crystal X-ray diffraction data. The Ti content, x, was deduced from the elementary cell volume, by applying the Végard law. Crystals were mainly untwinned and of good quality. The elementary cell of both, powders and crystals, was triclinic (P-1) and did not change with doping. DC electrical resistivity of the crystals was measured in a four-points (van der Pauw) configuration. DC magnetic susceptibility of the powders was measured in a SQUID magnetometer. The Ti doping was found to progressively smooth and finally to suppress the magnetic transitions occurring in the V4O7. The metal-insulator transitions observed in V4O7 and V5O9, at around 235 and 125 K respectively, were not observed in the doped crystals, thus indicating some significant change of the electronic structure of the V oxides. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystal growth features and properties of layered rare earth and barium cobaltatesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005G. L. Bychkov Abstract High quality single crystals of LnBaCo2O5+, (0 < , < 1) (Ln = Pr, Eu, Gd, Tb, Dy) with rectangular shape and average dimensions 5 mm × 5 mm × 1 mm were grown for the first time from overstoichiometric flux melt. The data on the primary crystallization field of most cobaltate phases, which appear in parts of corresponding Gibbs triangles in the range 1373 , 1523 K are discussed. Bulk single crystals of new phases HoBaCo4O7 up to 300 mm3, YBaCo4O7 and TbBaCo4O7 up to 10 mm3 in volume were grown first. A solution of these compounds structure has been found in the space group P63mc. For the Ln = Pr, Gd, Sm, Tb, Dy, Ho based systems under the liquidus line there are several other new cobaltate phases of both perovskite, and hexagonal crystal structure. Stability of the double perovskite phase and temperature of the antiferromagnetic , ferromagnetic phase transition in relation to the radius of rare earth ions are compared. The data on the exact analysis of chemical composition, including EDX and iodometric titration, as well as results on magnetic susceptibility of EuBaCo1- xAlxO5+, (0 < x < 0.3) are discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 1H and 19F nuclear magnetic resonance microimaging of water and chemical distribution in soil columnsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2007Myrna J. Simpson Abstract Nuclear magnetic resonance (NMR) microimaging is a noninvasive and nondestructive technique that has great potential for the study of soil processes. Hydrogen-1 NMR microimaging techniques were used to examine the distribution of water in four different soil cores. Fluorine-19 NMR microimaging is also used to study the transport of three model contaminants (hexafluorobenzene, sodium fluoride, and trifluralin) in soil columns. The 1H water distribution studies demonstrate that NMR microimaging can provide unique detail regarding the nature and location of water in soils. Image distortion (magnetic susceptibility) was observed for soil samples low in water (20,28% by weight) and that contained an iron content of 0.73 to 0.99%. Highly resolved images were obtained for the organic-rich soil (Croatan sample) and also facilitated the analysis of bound and unbound soil water through varying spin echo times. The contaminant studies with 19F NMR demonstrated that preferential flow processes can be observed in soil cores in as little as 16 h. Studies with hexafluorobenzene produced the highest quality images whereas the definition decreased over time with both trifluralin and sodium fluoride as the compounds penetrated the soil. Nonetheless, both 1H and 19F NMR microimaging techniques demonstrate great promise for studying soil processes. [source] Assembly of Dinuclear CuII Rigid Blocks by Bridging Azido or Poly(thiocyanato)chromates: Synthesis, Structures and Magnetic Properties of Coordination Polymers and Polynuclear ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2010Sergey V. Kolotilov Abstract Reaction of a dinuclear cationic copper(II) complex of 4,4,-[2-(3-hydroxyiminobutyl)imino]biphenyl [CuII2(LH)2]2+ with N3, resulted in the formation of a dinuclear azido [CuII2(LH)2(N3)2(H2O)2] complex or a 2D coordination polymer [CuII2(LH)2(N3)2]n. Reaction of the dinuclear complex with [CrIII(NCS)6]3, or [CrIII(NCS)4(NH3)2], produced a 2D polymer {[CuII2(LH)2(CH3CN)2]3[CrIII(NCS)6]2}n or a 1D chain, constructed from tetranuclear units {[CuII2(LH)2][CrIII(NCS)4(NH3)2]2}n. Structures of the compounds were determined by X-ray crystallography and complexes were characterised by the temperature dependency of the magnetic susceptibility and by ESR spectroscopy. Magnetic properties of homometallic compounds were fit with the model of a dimer with the Hamiltonian , = ,J,1·,2. For heterometallic complexes ,MT curves were fit as the superposition of magnetism resulting from both [CuII2(LH)2]2+ and the adjacent CrIII -containing anion. J values for the complexes lie in the range from ,12.74(4) to ,17.77(8) cm,1. It was shown that the 4,4,-biphenyl bridge efficiently mediates exchange interactions. [source] Divanadium(V) and Trapped Valence Linear Tetravanadium(IV,V,V,IV) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2009Anindita Sarkar Abstract In an acetonitrile/water mixture, reactions of the N,N,-bis(diacetyl)hydrazine (H2diah), bis(acetylacetonato)oxidovanadium(IV) [VO(acac)2] and monodentate N -coordinating heterocycles (hc) in a 1:2:2 mol ratio provide yellow divanadium(V) complexes of formula [(hc)O2V(,-diah)VO2(hc)] (1, hc = imidazole; 2, hc = pyrazole; 3, hc = 3,5-dimethyl pyrazole). On the other hand, in the same solvent mixture reactions of the same reagents in a 1:4:2 mol ratio produce green linear tetravanadium(IV,V,V,IV) complexes of formula [(acac)2OV(,-O)VO(hc)(,-diah)(hc)OV(,-O)VO(acac)2] (4, hc = imidazole; 5, hc = pyrazole; 6, hc = 3,5-dimethyl pyrazole). The complexes 1,6 have been characterized by elemental analysis, magnetic susceptibility, and various spectroscopic and electrochemical measurements. The X-ray crystal structures of 1, 3 and 6 have been determined. In all three structures, the diazine ligand diah2, is in trans configuration. Metal-centred bond parameters are consistent with the localized electronic structure of the two trans -bent {OV(,-O)VO}3+ cores present in 6. The pentavalent metal centres in 1, 3 and 6 are in a distorted trigonal-bipyramidal N2O3 coordination environment, while the terminal tetravalent metal centres in 6 are in a distorted octahedral O6 coordination sphere. The eight-line EPR spectra of the tetravanadium species (4,6) in dimethyl sulfoxide at ambient temperature indicate the rare valence localized electronic structure in the fluid phase. All the complexes are redox active and display metal-centred electron transfer processes in dimethyl sulfoxide solution. A reduction within ,0.78 to ,0.94 V (vs. Ag/AgCl) is observed for the divanadium(V) species 1,3, while a reduction and an oxidation are observed in the potential ranges ,0.82 to ,0.90 V and 0.96 to 1.12 V (vs. Ag/AgCl), respectively, for the tetravanadium species 4,6. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Ferrocene-Substituted [Mn4] Dicubane Single-Molecule MagnetsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2009Katie J. Heroux Abstract Two new mixed-valent [Mn4] single-molecule magnets (SMMs) have been synthesized by using N -alkylated diethanolamine ligands and ferrocenecarboxylic acid. Both complexes exhibit weak ferromagnetic exchange and appreciable axial zero-field splitting as evidenced by DC magnetic susceptibility and field-dependent magnetization measurements. A significant frequency-dependent out-of-phase signal in the AC susceptibility is also observed for both complexes, a feature that is characteristic of SMMs. The ground-state spin of each complex was determined from the DC data and extrapolation of the low-frequency AC data, giving a value of S = 8. This result is consistent with the previously reported and structurally similar S = 8 and S = 9 [Mn4] dicubane SMMs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Unconventional Spin Crossover in Dinuclear and Trinuclear Iron(III) Complexes with Cyanido and Metallacyanido BridgesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2009alitro Abstract A nonsymmetrical triamine, 1,6-diamino-4-azahexane, was Schiff-condensed with (X-substituted) o -salicylaldehyde to yield pentadentate ligands X-L5: salpet and MeBu-salpet. These ligands form mononuclear, dinuclear, and trinuclear FeIII complexes, whose structures were determined by single-crystal X-ray analysis. Of the mononuclear complexes, [FeIII(salpet)Cl] and [FeIII(MeBu-salpet)Cl] are high spin (S = 5/2), whereas [FeIII(salpet)CN]·MeOH is low spin (S = 1/2). The dinuclear and trinuclear complexes show a kind ofthermally induced spin crossover. The dinuclear complex [L5FeIII(CN)FeIIIL5](ClO4)·2H2O (L5 = salpet) is a mixed-spin assembly: the C -coordinated FeIII center is low spin (L) and the N -coordinated FeIII center is high spin (H) at low temperature; an antiferromagnetic interaction occurs between them. This LH reference state is mixed with the LL one. Upon heating, the system shows an increasing content of the HH state. Also, the dinuclear complex [L5FeIII(CN)FeIIIL5](BPh4)·2MeCN (L5 = MeBu-salpet) exhibits a spin transition between LH and HH spin pairs. The mixed-valence trinuclear complex [L5FeIII{FeII(CN)5(NO)}FeIIIL5]·0.5MeOH·3.75H2O (L5 = salpet) shows spin crossover with a residual high-spin fraction at liquid He temperature owing to the LL + LH ground state. The metallacyanido-bridged complex [L5FeIII{Ni(CN)4}FeIIIL5]·2MeOH (L5 = MeBu-salpet) contains a high-spin pair, HH, over the whole temperature interval with a ferromagnetic exchange interaction. A theoretical model was outlined that allows simultaneous fitting of all available experimental data (magnetic susceptibility, magnetization, high-spin mole fraction obtained from the Mössbauer spectra) on a common set of parameters. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Synthesis, Structural, Thermal and Magnetic Characterization of a Pyrophosphato-Bridged Cobalt(II) ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2008Oluwatayo F. Ikotun Abstract The reaction in water of CoII sulfate heptahydrate with 1,10-phenanthroline (phen) and sodium pyrophosphate (Na4P2O7) in a 2:4:1 stoichiometric ratio resulted in the crystallization of a neutral dinuclear CoII complex, {[Co(phen)2]2(,-P2O7)}·6MeOH (1), as revealed by a single-crystal X-ray diffraction study. The bridging pyrophosphato ligand between the two [Co(phen)2]2+ units in a bis(bidentate) coordination mode places the adjacent metal centers at 4.857 Å distance, and its conformation gives rise to intramolecular ,,, stacking interaction between adjacent phen ligands. Indeed, intermolecular ,,, stacking interactions between phen ligands from adjacent dinuclear complexes create a supramolecular 2D network in 1. Magnetic susceptibility measurements on a polycrystalline sample of 1 in the temperature range 1.9,295 K are typical of an overall antiferromagnetic coupling with a maximum of the magnetic susceptibility at 3.0 K. The analysis of the magnetic data in the whole temperature range allows the determination of the value of the intramolecular magnetic coupling (J = ,1.23 cm,1). The ability of the pyrophosphato ligand to mediate magnetic interactions between different first-row transition-metal ions when adopting the bis(bidentate) bridging mode is analyzed and discussed in the light of the small number of magneto-structural reports on this type of compound, bearing in mind the number of unpaired electrons and type of magnetic orbitals on each metal center. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Syntheses, Structures and Magnetic Properties of Dinuclear Copper(II),Lanthanide(III) Complexes Bridged by 2-Hydroxymethyl-1-methylimidazoleEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2008Wei-Xiong Zhang Abstract Three discrete dinuclear copper(II),lanthanide(III) complexes, namely, [CuLn(mmi)2(NO3)3(H2O)2] [Ln = La (1), Sm (2)] and [CuGd(mmi)2(NO3)2(H2O)3][NO3] (3) (Hmmi = 2-hydroxymethyl-1-methylimidazole) were synthesized and structurally characterized by X-ray diffraction analysis. In these complexes, dinuclear cores of CuII and LnIII are consolidated by a pair of ,-1,1- O bridges from mmi at a distance of 3.36,3.46 Å. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetization indicate that 1, 2 and 3 exhibit paramagnetic, antiferromagnetic and ferromagnetic behaviours, respectively. The value of the JCu,Gd coupling constant of 3 [8.7(1) cm,1] is fairly large, which is probably related to the small dihedral angles, , (5.0°), between the two planes of O,Cu,O and O,Gd,O in the CuO2Gd core.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] A Magnetostructural and Electrochemical Study of CuII and FeIII Complexes Containing a Tetradentate Aminebis(phenolate) Ligand with a Pendent Tetrahydrofuran GroupEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007Elham Safaei Abstract Ligating properties of a tetradentate ligand 2-{bis[(3,5-di- tert -butyl-2-hydroxybenzyl)amino]methyl}tetrahydrofuran,H2L, with [O,O,N,O]-donor atoms towards CuII and FeIII are described. The ligand H2L yields both mononuclear LFeIII(acac) (1) and dinuclear [L2FeIII2(,-OCH3)-(,-OH)] (2), [L2FeIII2(,-C2O4)] (3) and [L2CuII2] (4) complexes, which were characterized by various physical techniques, including X-ray diffraction, Mössbauer, electrochemical and magnetic susceptibility (2,290 K) measurements. That the electrochemical oxidations are ligand-centered, i.e. formation of phenoxyl radicals from the coordinated phenolates, have been shown by voltammetric methods. Complexes 2,4 display antiferromagnetic exchange coupling of the neighbouring metal centers. Comparison of the evaluated weak exchange coupling constants (J) with the literature values leads to the conclusion that the angle Cu,O,Cu, is not the only determinant for the nature of the exchange coupling and the capability of the bridging ligands as mediators for spin coupling in case of FeIII follows the order phenoxide , methoxide > hydroxide. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] | ||||||||||||||||||||||||||||||||||||||||