The anomalous paramagnetism of iron(III) NN-dialkyldithiocarbamates

1964 ◽  
Vol 17 (3) ◽  
pp. 294 ◽  
Author(s):  
AH White ◽  
R Roper ◽  
E Kokot ◽  
H Waterman ◽  
RL Martin
Keyword(s):  
Molecular Weight ◽  
Thermal Equilibrium ◽  
Room Temperature ◽  
Chemical Nature ◽  
Magnetic Moments ◽  
Chloroform Solution ◽  
Exchange Interactions ◽  
Magnetic Behaviour ◽  
Antiferromagnetic Exchange ◽  
Molecular Type

The magnetic moments of a series of 19 NN-disubstituted dithiocarbamates of iron(III), [Fe(S2C.NR?R")3], are anomalous in that their behaviour is neither "high-" nor "low-spin". Values of μeff. at room temperature lie between 2.62 and 5.83 B.M., the datum for each compound depending on the chemical nature of the substituents R' and R". This anomalous situation persists in benzene or chloroform solution. Cryoscopic and ebullioscopic molecular weight determinations establish that all the compounds are monomeric, which excludes the possibility that the magnetic behaviour arises from the presence of antiferromagnetic exchange interactions of either the inter- or intra-molecular type. These observations strongly support the early and generally overlooked work of Cambi who in 1932 proposed a thermal equilibrium between "magnetic isomers" of spins S = � and S = 5/2 to account for the origin of the magnetic anomaly.

Magnetism, electronic spectra, and structure of transition metal alkoxides. II. The preparation and magnetism of iron(III) alkoxides

1966 ◽  
Vol 19 (3) ◽  
pp. 363 ◽  
Author(s):  
RW Adams ◽  
RL Martin ◽  
G Winter
Keyword(s):  
Room Temperature ◽  
Benzene Solution ◽  
Magnetic Moments ◽  
Exchange Interactions ◽  
Metal Alkoxides ◽  
Antiferromagnetic Exchange ◽  
Crystal Data ◽  
Magnetic Susceptibilities ◽  
X Ray ◽  
The Core

The iron(III) alkoxides, Fe(OMe)3, Fe(OEt)3, and Fe(Obun)a have been prepared by a procedure alternative to those previously described in the literature. The trimeric nature of the three compounds in benzene is confirmed by cryoscopy, and preliminary X-ray single crystal data for the ethoxide are consistent with trimeric entities in the solid. The temperature variation of the magnetic susceptibilities for the three compounds follows the Curie-Weiss law between 90 and 300�K but with large values of θ=- 200�K. The unusually low magnetic moments vary markedly with temperature, and at room temperature remain depressed in benzene solution at peer μeff 4.4 B.M. This anomalous behaviour is ascribed to the presence of weak antiferromagnetic exchange interactions within the cluster of iron atoms which forms the core of the trimeric species Fe3(0R)9. The compounds are sensitive both to hydrolysis and to heating. Hydrolysis decreases and pyrolysis increases the magnetic susceptibility. This provides a convenient method for following the progress of both types of reaction.

Magnetic behaviour of synthetic Co2SiO4

2009 ◽  
Vol 65 (6) ◽  
pp. 664-675 ◽  
Author(s):  
Andrew Sazonov ◽  
Martin Meven ◽  
Vladimir Hutanu ◽  
Gernot Heger ◽  
Thomas Hansen ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Structure ◽  
Magnetic Moment ◽  
Mirror Symmetry ◽  
Magnetic Moments ◽  
Exchange Interactions ◽  
Magnetic Behaviour ◽  
Relative Strength ◽  
Antiferromagnetic Ordering ◽  
Polarized Neutron

Synthetic Co2SiO4 crystallizes in the olivine structure (space group Pnma) with two crystallographically non-equivalent Co positions and shows antiferromagnetic ordering below 50 K. We have investigated the temperature variation of the Co2SiO4 magnetic structure by means of non-polarized and polarized neutron diffraction for single crystals. Measurements with non-polarized neutrons were made at 2.5 K (below T N), whereas polarized neutron diffraction experiments were carried out at 70 and 150 K (above T N) in an external magnetic field of 7 T parallel to the b axis. Additional accurate non-polarized powder diffraction studies were performed in a broad temperature range from 5 to 500 K with small temperature increments. Detailed symmetry analysis of the Co2SiO4 magnetic structure shows that it corresponds to the magnetic (Shubnikov) group Pnma, which allows the antiferromagnetic configuration (Gx , Cy , Az ) for the 4a site with inversion symmetry \bar{1} (Co1 position) and (0,Cy ,0) for the 4c site with mirror symmetry m (Co2 position). The temperature dependence of the Co1 and Co2 magnetic moments obtained from neutron diffraction experiments was fitted in a modified molecular-field model. The polarized neutron study of the magnetization induced by an applied field shows a non-negligible amount of magnetic moment on the oxygen positions, indicating a delocalization of the magnetic moment from Co towards neighbouring O owing to superexchange coupling. The relative strength of the exchange interactions is discussed based on the non-polarized and polarized neutron data.

Thio derivatives of β-diketones and their metal chelates. X. The anomalous paramagnetism of some iron(III) chelates of monothio-β-diketones

1968 ◽  
Vol 21 (8) ◽  
pp. 1987 ◽  
Author(s):  
RKY Ho ◽  
SE Livingstone
Keyword(s):  
Iron Atom ◽  
Thermal Equilibrium ◽  
Room Temperature ◽  
Magnetic Behaviour ◽  
The Other ◽  
Ligand Field ◽  
Pairing Energy ◽  
Temperature Dependent ◽  
Magnetic Susceptibilities ◽  
Derivatives Of

The magnetic susceptibilities of the iron(111) chelates Fe(R1CS=CHCOR2)3 (R1 = Ph, p-MeC6H4, p-MeOC6H4, p-BrC6H4, 2-thienyl, 2-furyl, R2 = CF3; R1 = Ph, R2 = Ph, OEt) have been investigated over a temperature range. The iron(111) complex of ethyl thiobenzoylacetate (R1 = Ph, R2 = OEt) is of the high-spin type and obeys the Curie-Weiss law with θ =-8�k. The moments of the other complexes vary between 2.31 and 6.61 B.M. at room temperature and are temperature-dependent, ranging from 1.86 to 4.07 B.M. at 80�k, depending on the nature of R1 and R2 This behaviour is postulated to be due to a thermal equilibrium between the nearly equi-energetic spin-paired (t5/2g) and spin-free (t3/2ge2/g) configurations of the iron atom, resulting from the approximately equal magnitudes of the ligand field (Δ) and the pairing energy (π) in these complexes. The ligand field and consequently the magnetic behaviour are sensitive to the nature of R1 and R2: electron-withdrawing groups appear to be the most effective in increasing the population of the spin-paired configuration.

Neutron Laue diffraction study of the complex low-temperature magnetic behaviour of brownmillerite-type Ca2Fe2O5

2015 ◽  
Vol 48 (1) ◽  
pp. 273-279 ◽  
Author(s):  
Josie E. Auckett ◽  
Garry J. McIntyre ◽  
Maxim Avdeev ◽  
Hank De Bruyn ◽  
Thiam Teck Tan ◽  
...  
Keyword(s):  
Magnetic Structure ◽  
Short Range ◽  
Room Temperature ◽  
Easy Axis ◽  
Magnetic Moments ◽  
Magnetic Behaviour ◽  
Zero Field ◽  
Previous Suggestion ◽  
Laue Diffraction ◽  
Low Magnetic Field

The atomic and magnetic structure of brownmillerite Ca2Fe2O5has been refined against single-crystal neutron Laue diffraction data collected at 300, 100 and 10 K under zero-field and low-magnetic field (35 Oe = 35 × 103/4π A m−1) conditions. Ca2Fe2O5is a canted G-type antiferromagnet withPcm′n′ symmetry, the magnetic moments on Fe being directed approximately along the crystallographiccaxis at room temperature. The refinement results show clearly that this magnetic structure persists down toT= 10 K, despite a previous suggestion that an anomalous magnetic susceptibility enhancement observed in Ca2Fe2O5single crystals between 40 and 140 K might signify a reorientation of the antiferromagnetic easy axis fromctoabelow 40 K. Alternative explanations for this susceptibility anomaly are considered in terms of the evidence for partial or short-range loss of order in the anomalous regime, possibly due to the presence of multiple competing sublattice interactions.

scholarly journals New complexes of Co(II), Ni(II), Cu(II) with Schiff base N,N’-bis-(3-methoxy-saliciliden)-3,3’-dimethylbenzidine

2013 ◽  
Vol 78 (7) ◽  
pp. 947-957 ◽  
Author(s):  
Ionela Alan ◽  
Angela Kriza ◽  
Olguta Dracea ◽  
Nicolae Stanica
Keyword(s):  
Schiff Base ◽  
Thermogravimetric Analysis ◽  
Spectral Data ◽  
Elemental Analysis ◽  
Room Temperature ◽  
Magnetic Moments ◽  
Magnetic Behaviour ◽  
Molar Ratio ◽  
Square Planar ◽  
Perchlorate Complex

The new N,N?-bis-(3-methoxy-saliciliden)-3,3?-dimetilbenzidine (H2L) Schiff base and complexes with Co(II), Ni(II) and Cu(II) of type [M(HL)Cl(H2O)] (M=Co(II), Cu(II)) [M2L(H2O)4]X2 (M=Co(II), X=ClO4 and M=Cu(II), X=NO3) and [M2L(CH3COO)2] (M=Co(II), Ni(II), Cu(II)) were synthesised. The ligand and complexes were characterized by elemental analysis, conductibility measurements, magnetic moments at room temperature, IR, NMR, UV-VIS-NIR, EPR spectra and thermogravimetric analysis. A molar ratio of 1:1 or 1:2 between ligand and metal was determined from the elemental analysis. Except for perchlorate complex that behave as electrolyte, the rest of complexes are non-electrolytes. The spectral data suggest a tetrahedral, pseudo-tetrahedral or square-planar stereochemistry respectively, data confirmed by magnetic behaviour of complexes. The antimicrobial tests indicate a fungicide effect both for ligand and complexes.

Room temperature synthesis, crystal structure and selected properties of the new compound [Mn2(bipy)4SbS4](ClO4)

2016 ◽  
Vol 71 (5) ◽  
pp. 395-401 ◽  
Author(s):  
Carolin Anderer ◽  
Christian Näther ◽  
Wolfgang Bensch
Keyword(s):  
Crystal Structure ◽  
Aqueous Solutions ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Exchange Interactions ◽  
Antiferromagnetic Exchange ◽  
Synthetic Route ◽  
Pure Compound ◽  
Temperature Synthesis ◽  
Room Temperature Synthesis

AbstractThe new compound [Mn2(bipy)4SbS4](ClO4) was prepared by a new synthetic route for the preparation of thioantimonates(V) that can be used even at room temperature. Mixing aqueous solutions of [Mn(bipy)3](ClO4)2 and Na3SbS4 · 9H2O leads to immediate crystallization of the pure compound. In the structure an SbS43– anion acts as a tetradentate bridge connecting two Mn2+ cations of [Mn(bipy)3]2+ complexes (bipy = 2,2′-bipyridine). The compound features a hitherto unknown [Mn2(bipy)4SbS4]+ cation. Bipy ligands of adjacent cations are arranged parallel to each other leading to weak off-center parallel π-π interactions stabilizing the crystals. Magnetic measurements indicate weak antiferromagnetic exchange interactions between the Mn2+ centers.

Degradation in a Methyl-phenyl Co-Polymeric Polysilane for LED Applications

2003 ◽  
Vol 769 ◽  
Author(s):  
Asha Sharma ◽  
Deepak ◽  
Monica Katiyar ◽  
Satyendra Kumar ◽  
V. Chandrasekhar ◽  
...  
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Light Source ◽  
Room Temperature ◽  
Light Exposure ◽  
Room Temperature Photoluminescence ◽  
Pl Spectrum ◽  
Pl Intensity ◽  
Methyl Phenyl

AbstractThe optical degradation of polysilane copolymer has been studied in spin cast thin films and solutions using light source of 325 nm wavelength. The room temperature photoluminescence (PL) spectrum of these films show a sharp emission at 368 nm when excited with a source of 325 nm. However, the PL intensity deteriorates with time upon light exposure. Further the causes of this degradation have been examined by characterizing the material for its transmission behaviour and changes occurring in molecular weight as analysed by GPC data.

scholarly journals 3D Metal–Organic Frameworks Based on Co(II) and Bithiophendicarboxylate: Synthesis, Crystal Structures, Gas Adsorption, and Magnetic Properties

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1269
Author(s):  
Vadim A. Dubskikh ◽  
Anna A. Lysova ◽  
Denis G. Samsonenko ◽  
Alexander N. Lavrov ◽  
Konstantin A. Kovalenko ◽  
...  
Keyword(s):  
Room Temperature ◽  
Gas Adsorption ◽  
Magnetic Moments ◽  
Bet Surface Area ◽  
Separation Performance ◽  
Bridging Ligands ◽  
Magnetization Data ◽  
Metal Organic ◽  
Ch4 Adsorption ◽  
Gas Separation Performance

Three new 3D metal-organic porous frameworks based on Co(II) and 2,2′-bithiophen-5,5′-dicarboxylate (btdc2−) [Co3(btdc)3(bpy)2]·4DMF, 1; [Co3(btdc)3(pz)(dmf)2]·4DMF·1.5H2O, 2; [Co3(btdc)3(dmf)4]∙2DMF∙2H2O, 3 (bpy = 2,2′-bipyridyl, pz = pyrazine, dmf = N,N-dimethylformamide) were synthesized and structurally characterized. All compounds share the same trinuclear carboxylate building units {Co3(RCOO)6}, connected either by btdc2– ligands (1, 3) or by both btdc2– and pz bridging ligands (2). The permanent porosity of 1 was confirmed by N2, O2, CO, CO2, CH4 adsorption measurements at various temperatures (77 K, 273 K, 298 K), resulted in BET surface area 667 m2⋅g−1 and promising gas separation performance with selectivity factors up to 35.7 for CO2/N2, 45.4 for CO2/O2, 20.8 for CO2/CO, and 4.8 for CO2/CH4. The molar magnetic susceptibilities χp(T) were measured for 1 and 2 in the temperature range 1.77–330 K at magnetic fields up to 10 kOe. The room-temperature values of the effective magnetic moments for compounds 1 and 2 are μeff (300 K) ≈ 4.93 μB. The obtained results confirm the mainly paramagnetic nature of both compounds with some antiferromagnetic interactions at low-temperatures T < 20 K in 2 between the Co(II) cations separated by short pz linkers. Similar conclusions were also derived from the field-depending magnetization data of 1 and 2.

scholarly journals Metal- and Oxidant-Free Photoinduced Aromatic Trifluoromethylation Performed in Aerated Gel Media: Determining the Effects on Yield and Selectivity

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 29 ◽  
Author(s):  
Alex Abramov ◽  
Hendrik Vernickel ◽  
César Saldías ◽  
David Díaz Díaz
Keyword(s):  
Molecular Weight ◽  
Room Temperature ◽  
Homogeneous Solution ◽  
Product Distribution ◽  
Blocking Effect ◽  
Low Molecular Weight ◽  
Metal Free ◽  
Potential Benefits ◽  
Media Concentration ◽  
Reaction Media

In this work we have investigated the potential benefits of using supramolecular gel networks as reaction media to carry out air-sensitive metal-free light-induced trifluoromethylation of six-membered (hetero)arenes under aerobic conditions. This reaction was performed at room temperature (RT) using sodium triflinate (CF3SO2Na, Langlois’ reagent) as a source of radicals and diacetyl as electron donor. The effects of confinement in gel media, concentration of reactants, and type of light source on yield and product distribution were evaluated and compared to the results obtained in homogeneous solution. Four different low molecular weight (LMW) gelators were employed in this study. The results confirmed the blocking effect of the gel medium against reaction quenching by external oxygen, as well as a certain control on the kinetics and selectivity.

scholarly journals Manganese Fluorene Phosphonates: Formation of Isolated Chains

Inorganics ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 92 ◽  
Author(s):  
Clarisse Bloyet ◽  
Jean-Michel Rueff ◽  
Vincent Caignaert ◽  
Bernard Raveau ◽  
Jean-François Lohier ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Hydrogen Bonds ◽  
Phosphonic Acid ◽  
Van Der Waals ◽  
Exchange Interactions ◽  
Van Der Waals Interactions ◽  
Antiferromagnetic Exchange ◽  
Hydrothermal Conditions ◽  
Hirshfeld Surfaces ◽  
Nitrate Tetrahydrate

9,9-dimethylfluorenyl-2-phosphonic acid 1 was reacted with manganese nitrate tetrahydrate to produce under hydrothermal conditions the crystalline manganese phosphonate Mn(H2O)2[O2(OH)PC15H13]2·2H2O which crystallize in the P21/c space group. This compound is a rare example of Mn-phosphonate material featuring isolated chains. The interactions between these chains containing the 9,9-dimethylfluorenyl moieties, result from Van der Waals interactions involving the fluorene ligands and C···H–C hydrogen bonds as revealed by Hirshfeld Surfaces. This material features antiferromagnetic exchange interactions as revealed by the magnetic susceptibility as a function of the temperature.

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