Metal pyrazolate polymers. Part 3. Synthesis and study of Cu(I) and Cu(II) complexes of 4-Xdmpz (where X = H, Cl, Br, I, and CH3 for Cu(I) and X = H, Cl, Br, and CH3 for Cu(II); dmpz = 3,5-dimethylpyrazolate)

1992 ◽  
Vol 70 (4) ◽  
pp. 1121-1128 ◽  
Author(s):  
Martin K. Ehlert ◽  
Alan Storr ◽  
Robert C. Thompson
Keyword(s):  
Magnetic Susceptibility ◽  
Spectroscopic Studies ◽  
Magnetic Data ◽  
Antiferromagnetic Coupling ◽  
Polymeric Chain ◽  
Differential Scanning Calorimetric ◽  
Scanning Electron Micrographs ◽  
Coupling Constant ◽  
Abrupt Decrease ◽  
Calorimetric Studies

The copper(I) complexes [Cu(4-Xdmpz)]3 (where X = H, Cl, Br, I and CH3; dmpz = 3,5-dimethylpyrazolate) and the copper(II) complexes [Cu(4-Xdmpz)2]x have been synthesized and characterized. Qualitative solubility, infrared spectroscopic, and differential scanning calorimetric studies are reported for all complexes. Mass spectra support trimeric formulations for the copper(I) complexes. Scanning electron micrographs and powder X-ray diffractograms have been recorded for the copper(II) compounds. Electronic and EPR spectroscopic studies as well as magnetic susceptibility studies from 2 to 300 K are also reported for the copper(II) compounds, which are proposed to have polymeric chain structures. The magnetic data reveal strong antiferromagnetic interactions in all four of the copper(II) compounds. The data have been analysed employing an isotropic Heisenberg model for antiferromagnetic coupling in extended chain polymers. Values of the exchange coupling constant, J, are determined as −58, −61, −66, and −66 cm−1 for the X = H, CH3, Cl, and Br complexes respectively. The X = Cl compound exhibits an abrupt decrease in magnetic susceptibility below 40 K and possible causes of this anomalous behaviour are discussed.

Structure and magnetic exchange in poly-bis(pyrazine)bis(methanesulfonato-O)-copper(II). One-dimensional exchange in a two-dimensional polymer

1987 ◽  
Vol 65 (2) ◽  
pp. 420-426 ◽  
Author(s):  
John S. Haynes ◽  
Steven J. Rettig ◽  
John R. Sams ◽  
Robert C. Thompson ◽  
James Trotter
Keyword(s):  
Magnetic Susceptibility ◽  
Heavy Atom ◽  
Linear Chain ◽  
Differential Scanning Calorimetric ◽  
Magnetic Exchange ◽  
Magnetic Susceptibility Data ◽  
Susceptibility Data ◽  
Pyridine Complex ◽  
Calorimetric Studies ◽  
Square Array

Crystals of poly-bis(pyrazine)bis(methanesulfonato-O)copper(II) are orthorhombic, a = 8.199(1), b = 13.130(1), c = 6.913(1) Å, Z = 2, space group Pnnm. The structure was solved by conventional heavy atom methods and was refined by full-matrix least-squares procedures to R = 0.025 and Rw = 0.033 for 1226 reflections with I ≥ 3σ(I). The complex contains parallel sheets, each sheet consisting of a square array of copper(II) ions bridged by two types of bidentate pyrazine ligands. The CuN4O2 chromophore is tetragonally elongated; the equatorial plane contains two pyrazine nitrogen atoms (Cu—N(1) = 2.058(2) Å) and two oxygen atoms from monodentate methanesulfonate ligands (Cu—O(1) = 1.956(1) Å); the axial sites are occupied by bridging pyrazine groups with significantly longer Cu—N bond lengths (Cu—N(2) = 2.692(2) Å) Magnetic susceptibility studies (82 to 4.2 K) reveal antiferromagnetic behaviour with a susceptibility maximum at about 6.2 K. Exchange coupling in the complex is considered to take place primarily via the more strongly bound, equatorially coordinated pyrazine ligands. Analysis of the magnetic susceptibility data according to a Heisenberg linear chain of interacting S = 1/2 spins yields best fit values of J = −3.82 cm−1 and g = 2.13. Vibrational and electronic spectroscopic and differential scanning calorimetric studies on the title compound and, for comparison, on the related mononuclear pyridine complex, bis(methanesulfonato)-tetrakis(pyridine)copper(II), are also reported.

Antiferromagnetic exchange in manganese(II) monophenylphosphinate and the effects of cadmium doping

1989 ◽  
Vol 67 (7) ◽  
pp. 1239-1243 ◽  
Author(s):  
Jlng-Long Du ◽  
Robert C. Thompson
Keyword(s):  
Magnetic Susceptibility ◽  
Theoretical Models ◽  
Magnetic Data ◽  
Coupling Constant ◽  
Scanning Calorimetry ◽  
Manganese Compound ◽  
Linear Chains ◽  
Magnetic Chain ◽  
Metal Materials ◽  
Polymeric Structures

Mn[H(C6H5)PO2]2, its cadmium analogue, and mixed metal materials of composition Mn1−xCdx[H(C6H5)PO2]2 (x = 0.005, 0.01, 0.09, 0.27, and 0.47) have been synthesized and characterized by X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry and low-temperature (4.2 to 80 K) magnetic susceptibility studies. The materials are shown to be isomorphous and are considered to have polymeric structures in which chains of metal atoms are linked by bridging phosphinate groups. The pure manganese compound is antiferromagnetic (maximum in xm at ~35 K) and the magnetic data for the compound have been analyzed according to two theoretical models for linear chains of antiferromagnetically coupled manganese(II) (d5, spin-free) ions. The Wagner and Friedberg model gives J = −3.00 cm−1 and the Weng model gives J = −2.78 cm−1. The effects of replacing Mn2+ by Cd2+ ions in the polymer is to increase the magnetic susceptibility (per mol of Mn) at all temperatures. Analysis of the data as a function of Cd doping indicates the incorporation of a paramagnetic component to the susceptibility which increases with increasing Cd content. In addition, the absolute value of the exchange coupling constant appears to decrease as the Cd content increases. These effects are considered in terms of a random defect model in which the replacement of Mn ions in the polymer by Cd ions results in the formation of Cd ion separated finite magnetic chain fragments. Keywords: manganese(II) monophenylphosphinate, magnetic properties, coordination polymer, cadmium doped antiferromagnet.

Polynuclear pyrazolate complexes of copper. Crystal and molecular structures of [Cu(tmpz)]3, [Cu(3-CO2dmpz)(tmpzH)]2Cu, and [Cu(4-Br-3-CO2mepz)(4-Br-dmpzH)2]2 (where mepz = methylpyrazolate, dmpz = dimethylpyrazolate, and tmpz = trimethylpyrazolate) and magnetic susceptibility studies on the dinuclear complex

1992 ◽  
Vol 70 (8) ◽  
pp. 2161-2173 ◽  
Author(s):  
Martin K. Ehlert ◽  
Steven J. Rettig ◽  
Alan Storr ◽  
Robert C. Thompson ◽  
James Trotter
Keyword(s):  
Magnetic Susceptibility ◽  
Exchange Coupling ◽  
Bulk Sample ◽  
Molecular Structures ◽  
Antiferromagnetic Coupling ◽  
Coupling Constant ◽  
Copper Metal ◽  
Copper Crystal ◽  
Space Group ◽  
Crystalline Forms

The reaction of molten trimethylpyrazole (tmpzH) with copper metal shot in air yields a mixture of the trinuclear copper(I) complex [Cu(tmpz)]3, 1, and the trinuclear copper(I/II) complex [Cu(3-CO2dmpz)(tmpzH)]2Cu, 2 (where dmpz is dimethylpyrazolate). Crystals of 1 are monoclinic, a = 8.403(3), b = 22.453(2), c = 11.362(2) Å, (3 = 95.83(2)°, Z = 4, space group P21/c. Crystals of 2 are triclinic, a = 10.988(3), b = 11.009(2), c = 6.457(1) Å, α = 103.13(2)°, β = 103.02(2)°, γ = 108.70(2)°, Z = 1, space group [Formula: see text]. The reaction of molten 4-bromodimethylpyrazole (4-BrdmpzH) with copper metal shot in air gave the binuclear copper(II) complex [Cu(4-Br-3-CO)2mepz)(4-BrdmpzH)2]2, 3 (where mepz is methylpyrazolate). There are two crystalline forms of 3:3a, triclinic, a = 10.152(3), b = 13.068(3), c = 10.033(3) Å, a = 112.38(2)°, (3 = 116.46(2)°, γ = 70.29(2)°, Z = 1, space group [Formula: see text]; and 3b, monoclinic, a = 13.470(1), b = 16.005(2), c = 20.174(1) Å, β = 98.142(6)°, Z = 4, space group C2/c. Magnetic susceptibility studies on a bulk sample of 3 (2.0–300 K) revealed antiferromagnetic coupling between the double pyrazolate bridged copper centres and analysis of the data according to a Heisenberg model for coupled pairs of S = 1/2 metal ions gave −75.4 cm−1 for the value of the exchange coupling constant, J. The crystal structures of 1, 2, 3a, and 3b were solved by the Patterson method and were refined by full-matrix least-squares procedures to final R values of 0.036, 0.056, 0.042, and 0.042 for 2265, 1764, 2011, and 2575 reflections with I ≥ 3σ(I), respectively.

Transition metal azolates from metallocenes. Part 3: Polymeric manganese(II) and nickel(II) pyrazolates; synthesis, characterization, and magnetochemistry

1998 ◽  
Vol 76 (8) ◽  
pp. 1130-1137 ◽  
Author(s):  
Alan Storr ◽  
David A Summers ◽  
Robert C Thompson
Keyword(s):  
Metal Ions ◽  
Exchange Coupling ◽  
Variable Temperature ◽  
Indirect Evidence ◽  
Inert Atmosphere ◽  
Magnetic Data ◽  
Antiferromagnetic Coupling ◽  
Coupling Constant ◽  
Direct Reactions ◽  
Nickel Manganese

Direct reactions of nickelocene and manganocene with molten pyrazoles in an inert atmosphere or under vacuum have led to the isolation of the following metal pyrazolate compounds: [Ni(4-Xpz)2]x (where X = H, Cl and pz = pyrazolate); [M(4-Xdmpz)2]x (where X = H, CH3, Cl, Br and M = Ni, Mn anddmpz = 3,5-dimethylpyazolate); and [Mn(4-Xpz)2(4-XpzH)]x (where X = Cl, Br and pzH = pyrazole). On the basis of indirect evidence all compounds are considered to have extended chain structures with metal ions linked in chains by double bridging pyrazolates. The two [Ni(4-Xpz)2]x compounds are diamagnetic while all others are paramagnetic. Variable temperature magnetic susceptibility studies on the paramagnetic compounds reveal antiferromagnetic coupling between neighbouring metal ions. Analysis of the magnetic data (Hamiltonian of the form H = -2J sum Si·Sj) yields values of the exchange coupling constant J of -14 to -17 cm -1for the [Ni(4-Xdmpz)2]x compounds, -1.2 to -2.1 cm-1 for the [Mn(4-Xdmpz)2]x compounds, and -0.41 cm-1 for the [Mn(4-Xpz)2(4-XpzH)]x compounds.Key words: nickel, manganese, manganocene, nickelocene, pyrazolates, antiferromagnetic exchange.

An Augmented Iteratively Re-weighted and Refined Least Squares Method for lp Minimization Problem in Inverse Modeling of Potential Field Magnetic Data

2020 ◽  
Vol 1 (3) ◽  
Author(s):  
Maysam Abedi
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Least Squares ◽  
Minimization Problem ◽  
Potential Field ◽  
Field Data ◽  
Least Squares Method ◽  
Porphyry Copper ◽  
Magnetic Data ◽  
Magnetic Field Data

The presented work examines application of an Augmented Iteratively Re-weighted and Refined Least Squares method (AIRRLS) to construct a 3D magnetic susceptibility property from potential field magnetic anomalies. This algorithm replaces an lp minimization problem by a sequence of weighted linear systems in which the retrieved magnetic susceptibility model is successively converged to an optimum solution, while the regularization parameter is the stopping iteration numbers. To avoid the natural tendency of causative magnetic sources to concentrate at shallow depth, a prior depth weighting function is incorporated in the original formulation of the objective function. The speed of lp minimization problem is increased by inserting a pre-conditioner conjugate gradient method (PCCG) to solve the central system of equation in cases of large scale magnetic field data. It is assumed that there is no remanent magnetization since this study focuses on inversion of a geological structure with low magnetic susceptibility property. The method is applied on a multi-source noise-corrupted synthetic magnetic field data to demonstrate its suitability for 3D inversion, and then is applied to a real data pertaining to a geologically plausible porphyry copper unit.  The real case study located in  Semnan province of  Iran  consists  of  an arc-shaped  porphyry  andesite  covered  by  sedimentary  units  which  may  have  potential  of  mineral  occurrences, especially  porphyry copper. It is demonstrated that such structure extends down at depth, and consequently exploratory drilling is highly recommended for acquiring more pieces of information about its potential for ore-bearing mineralization.

scholarly journals Differential scanning calorimetric studies on thermal behaviors of myofibrillar proteins.

1985 ◽  
Vol 51 (11) ◽  
pp. 1841-1846 ◽  
Author(s):  
Takayuki AKAHANE ◽  
Satoshi CHIHARA ◽  
Tamotsu P. NIKI ◽  
Takeshi SANO ◽  
Takahide TSUCHIYA ◽  
...  
Keyword(s):  
Differential Scanning Calorimetric ◽  
Myofibrillar Proteins ◽  
Thermal Behaviors ◽  
Calorimetric Studies

Magnetic Susceptibilities of 2T2 Ions. Part 1

1972 ◽  
Vol 50 (10) ◽  
pp. 1468-1471 ◽  
Author(s):  
Alan D. Westland
Keyword(s):  
Magnetic Susceptibility ◽  
Excited State ◽  
Reduction Factor ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Coupling Constant ◽  
Magnetic Susceptibilities

An expression for the magnetic susceptibility of octahedral d1 complexes is derived exactly in terms of an orbital reduction factor k taking into account the presence of the formal 2E excited state. Sample calculations show that the improved expression gives results for susceptibility which are lower at times by several percent from those given by previous expressions. The results given by Figgis using Kotani's method are adequately precise when the spin–orbit coupling constant is no larger than ~0.1 Dq.

Interaction of a peptide model of a hydrophobic transmembrane .alpha.-helical segment of a membrane protein with phosphatidylcholine bilayers: Differential scanning calorimetric and FTIR spectroscopic studies

Biochemistry ◽  
1992 ◽  
Vol 31 (46) ◽  
pp. 11579-11588 ◽  
Author(s):  
Yuan Peng Zhang ◽  
Ruthven N. A. H. Lewis ◽  
Robert S. Hodges ◽  
Ronald N. McElhaney
Keyword(s):  
Membrane Protein ◽  
Spectroscopic Studies ◽  
Differential Scanning Calorimetric ◽  
Helical Segment

scholarly journals Differential Scanning Calorimetric Studies on Chemically Cross-linked Sodium Carboxymethylcellulose Hydrogels

2008 ◽  
Vol 65 (7) ◽  
pp. 477-482
Author(s):  
Toru ONISHI ◽  
Hyoe HATAKEYAMA ◽  
Tatsuko HATAKEYAMA
Keyword(s):  
Differential Scanning Calorimetric ◽  
Sodium Carboxymethylcellulose ◽  
Calorimetric Studies

SEM Observations and Differential Scanning Calorimetric Studies of New and Sterilized Nickel-Titanium Rotary Endodontic Instruments

2006 ◽  
Vol 32 (7) ◽  
pp. 675-679 ◽  
Author(s):  
Georgia B. Alexandrou ◽  
Konstantinos Chrissafis ◽  
Leonidas P. Vasiliadis ◽  
Eleni Pavlidou ◽  
E.K. Polychroniadis
Keyword(s):  
Nickel Titanium ◽  
Differential Scanning Calorimetric ◽  
Calorimetric Studies
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