Synthesis, spectroscopic and magnetic properties of some pyrazine-bridged iron(II) sulfonate complexes

1988 ◽  
Vol 66 (8) ◽  
pp. 2079-2087 ◽  
Author(s):  
John S. Haynes ◽  
John R. Sams ◽  
Robert C. Thompson
Keyword(s):  
Heisenberg Model ◽  
Hyperfine Splitting ◽  
Variable Temperature ◽  
Magnetic Data ◽  
Antiferromagnetic Coupling ◽  
Antiferromagnetic Exchange ◽  
Two Dimensional ◽  
Scanning Calorimetry ◽  
Best Fit ◽  
Magnetic Hyperfine Splitting

Six new pyrazine-bridged complexes of iron(II) have been prepared and studied using magnetic susceptibility, differential scanning calorimetry, and vibrational, electronic, and Mössbauer spectroscopic methods. Fe(pyz)(CF3SO3)2 exhibits a susceptibility maximum at 4.4 K and analysis of the magnetic data according to a two-dimensional S = 2 system in the (isotropic) Heisenberg limit yields best-fit values of J = −0.26 cm−1 and g = 2.20. Variable temperature Mössbauer spectra between 4.2 and 1.6 K are also reported for this compound and show the onset of magnetic hyperfine splitting below ~3.8 K. Analysis of magnetic data for Fe(pyz)2(CH3SO3)2 and Fe(pyz)2(CF3SO3)2•CH3OH according to the two-dimensional Heisenberg model also indicates the presence of weak antiferromagnetic exchange in these complexes (J = −0.18 and −0.20 cm−1, respectively). No clear evidence for magnetic concentration was obtained from our studies on Fe(pyz)2(CIO4)2, Fe(pyz)(p-CH3C6H4SO3)2, and Fe(pyz)(p-CH3C6H4SO3)2•2CH3OH; any antiferromagnetic coupling in these complexes must be considerably weaker than in the other complexes studied.

Magnetic concentration and polymorphism in di-n-octyl-, di-n-decyl-, and di-n-dodecylphosphinates of copper(II)

1985 ◽  
Vol 63 (5) ◽  
pp. 1111-1117 ◽  
Author(s):  
John S. Haynes ◽  
Katherine W. Oliver ◽  
Robert C. Thompson
Keyword(s):  
Differential Scanning Calorimetry ◽  
Magnetic Susceptibility ◽  
Heisenberg Model ◽  
Variable Temperature ◽  
Electronic Spectroscopy ◽  
Chain Structure ◽  
Magnetic Data ◽  
Scanning Calorimetry ◽  
Extended Chain ◽  
Linear Chains

Phosphinates of copper(II) of the type Cu(R2PO2)2 where R is n-octyl, n-decyl, and n-dodecyl have been synthesized and characterized by differential scanning calorimetry, vibrational and electronic spectroscopy, and variable temperature (300 to 4.2 K) magnetic susceptibility studies. Each of these compounds was obtained in distinct α and β structural forms. All materials appear to have the double phosphinate bridged extended chain structure and the magnetic data have been successfully analyzed according to the isotropic Heisenberg model for linear chains. The α forms exhibit antiferromagnetic behaviour with J values of −25, −29, and −29 cm−1 for the octyl, decyl, and dodecyl derivatives respectively. The β forms are ferromagnetic and have corresponding J values of 1.8, 2.1, and 2.3 cm−1 respectively. Magneto-structural correlations in these extended chain coordination polymers are discussed.

Oligometallic cobalt 3,5-dimethylpyrazolate complexes: synthesis, structural and magnetic studies

1993 ◽  
Vol 71 (9) ◽  
pp. 1425-1436 ◽  
Author(s):  
Martin K. Ehlert ◽  
Steven J. Rettig ◽  
Alan Storr ◽  
Robert C. Thompson ◽  
James Trotter
Keyword(s):  
Magnetic Data ◽  
Antiferromagnetic Coupling ◽  
Antiferromagnetic Exchange ◽  
Nearest Neighbour ◽  
X Ray Diffraction ◽  
Magnetic Studies ◽  
Dimer Model ◽  
Space Group ◽  
X Ray ◽  
Susceptibility Data

Three oligometallic 3,5-dimethylpyrazolate (dmpz) bridged Co(II) compounds have been synthesized and characterized spectroscopically: dimeric [Co(dmpz)2(Hdmpz)]2, the related oligometallic compound, Co(dmpz)2•0.344(Hdmpz), and the trimetallic [Co(dmpz)2Cl(Hdmpz)]2Co. The first and last of these compounds have been studied magnetically and by single crystal X-ray diffraction. Crystals of [Co(dmpz)2(Hdmpz)]2 are orthorhombic, a = 17.022(1), b = 29.224(2), c = 13.576(3) Å, Z = 8, space group Fddd; and those of [Co(dmpz)2Cl(Hdmpz)]2Co are triclinic, a = 11.742(3), b = 18.604(4), c = 8.950(2) Å, α = 99.76(2)°, β = 102.32(2)°, γ = 93.36(2)°, Z = 2, space group [Formula: see text] The structures were solved by the Patterson method and were refined by full-matrix least-squares procedures to R = 0.035 and 0.042 (Rw = 0.034, 0.047) for 938 and 3853 reflections with I ≥ 3σ(F2), respectively. Magnetic susceptibility studies on the dimeric and trimetallic complex show them to exhibit antiferromagnetic behaviour. Analysis of the magnetic data (2– 300 K) for the trimetallic complexes reveals antiferromagnetic coupling between the terminal and central Co(II) ions with J (Heisenberg) ≈ −3 cm−1. Either intramolecular next-nearest neighbour or intermolecular antiferromagnetic exchange is also present in this compound. The dimeric complex shows significant antiferromagnetic exchange between cobalt centres. Susceptibility data over the range 12–300 K are adequately modelled with the Ising S = 1/2 dimer model (J ≈ −23 cm−1).

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.

Self-Assembly of Hydrogels From Elastin-Mimetic Block Copolymers

2002 ◽  
Vol 724 ◽  
Author(s):  
Elizabeth R. Wright ◽  
R. Andrew McMillan ◽  
Alan Cooper ◽  
Robert P. Apkarian ◽  
Vincent P. Conticello
Keyword(s):  
Block Copolymers ◽  
Self Assembly ◽  
Triblock Copolymers ◽  
Variable Temperature ◽  
Inverse Temperature ◽  
Temperature Transition ◽  
Scanning Calorimetry ◽  
Design Synthesis ◽  
Inverse Temperature Transition ◽  
Functional Biomaterials

AbstractTriblock copolymers have traditionally been synthesized with conventional organic components. However, triblock copolymers could be synthesized by the incorporation of two incompatible protein-based polymers. The polypeptides would differ in their hydrophobicity and confer unique physiochemical properties to the resultant materials. One protein-based polymer, based on a sequence of native elastin, that has been utilized in the synthesis of biomaterials is poly (Valine-Proline-Glycine-ValineGlycine) or poly(VPGVG) [1]. This polypeptide has been shown to have an inverse temperature transition that can be adjusted by non-conservative amino acid substitutions in the fourth position [2]. By combining polypeptide blocks with different inverse temperature transition values due to hydrophobicity differences, we expect to produce amphiphilic polypeptides capable of self-assembly into hydrogels. Our research examines the design, synthesis and characterization of elastin-mimetic block copolymers as functional biomaterials. The methods that are used for the characterization include variable temperature 1D and 2D High-Resolution-NMR, cryo-High Resolutions Scanning Electron Microscopy and Differential Scanning Calorimetry.

scholarly journals Unraveling the fine-tuned lemon coloration of a pierid butterfly Catopsilia pomona

Microscopy ◽  
2017 ◽  
Vol 66 (6) ◽  
pp. 414-423
Author(s):  
Monalisa Mishra ◽  
Ashutosh Choudhury ◽  
P Sagar Achary ◽  
Harekrushna Sahoo
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Variable Temperature ◽  
Wing Pattern ◽  
Physical Composition ◽  
Different Types ◽  
Microscopy Techniques ◽  
Pierid Butterfly ◽  
Best Fit ◽  
Scanning Electron

Abstract Butterflies wings possess different types of scales to perform diverse functions. Each scale has many nano and microstructures, which interferes with light, resulting in unique coloration for each butterfly. Besides coloration, the arrangement of scales further helps in giving better survivability. Thus, analysis of wing pattern provides an overall idea about adaptation and activity of the animal. The current study deciphers the structure and composition of a wing of a pierid butterfly Catopsilia pomona, which remains active at 42°C at which temperature all other butterflies face a tougher task for existence. In order to know the relation between survivability and adaptation in the wing, we have investigated the structural and physical composition of the wing of C. pomona under optical spectroscopy (absorption, reflectance and transmittance) along with microscopy techniques (optical and scanning electron microscopy), which are not described in earlier studies. The current findings reveal unique structural arrangement within scales to provide the best fit to the animal in variable temperature.

Sign in / Sign up

Export Citation Format

Share Document