Spin Crossover in Iron(II) Complexes of 1-Methyl-2-(Pyridin-2-Yl)imidazole and 1-Methyl-2-(Pyridin-2-Yl)benzimidazole

1987 ◽  
Vol 40 (5) ◽  
pp. 775 ◽  
Author(s):  
KH Sugiyarto ◽  
HA Goodwin
Keyword(s):  
Solid State ◽  
Field Strength ◽  
Electronic Spectra ◽  
Spin Crossover ◽  
Elevated Temperatures ◽  
Electronic States ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Forbidden Transition ◽  
Imidazole System

Tris (ligand)iron(II) complexes of 1-methyl-2-(pyridin-2-y1) imidazole and 1-methyl-2-(pyridin-2- y1) benzimidazole are diamagnetic and intensely coloured in solution. Magnetic and electronic and Mossbauer spectral data for the complexes in the solid state show an anomalous temperature-dependence, slight for the imidazole system but strong for the benzimidazole system, which indicates population at elevated temperatures of quintet electronic states. The spin crossover in these systems is displayed to higher temperatures compared to that in the complexes of the unsubstituted ligands. Data from the electronic spectra of the nickel(II) complexes provide a basis for comparison of the behaviour of both the substituted and unsubstituted ligands. These spectra reveal a strong contribution from the 3A2g → lAg spin-forbidden transition which is expected for ligands which exert a field strength close to the iron(II) crossover value.

Steric Effects of the Spin State of Iron(II) in Complexes of Substituted Bipyridine Derivatives

1991 ◽  
Vol 44 (11) ◽  
pp. 1539 ◽  
Author(s):  
D Onggo ◽  
HA Goodwin
Keyword(s):  
Field Strength ◽  
Spectral Data ◽  
Thermal Equilibrium ◽  
Steric Effects ◽  
Spin States ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Thermally Induced ◽  
Infrared Spectral ◽  
Derivatives Of

Iron(II) and nickel(II) complexes of dimethyl 2,2′-bipyridine-3,3′-dicarboxylate (dmbc), 1,1′-biisoquinoline (biq), 6,6′-dimethyl-2,2′-bipyridine (dmbpy) and 4,4′6,6′-tetramethyl-2,2′- bipyridine (tmbpy) have been prepared. [FeN6]2+ derivatives of dmbc and biq were isolated as solid salts. These show anomalous temperature dependence of their magnetism and Mossbauer spectra which has been interpreted in terms of a thermally induced singlet (1A1) ↔ quintet (5T2) transition. The transition is also observed for [Fe(biq)3][BF4]2 in solution and has been analysed in terms of a thermal equilibrium involving the two spin states. Electronic spectral data for the [NiN6]2+ derivatives indicate values for the field strength of these ligands which are consistent with the appearance of the transition in the iron(II) species. Both dmbpy and tmbpy yield only bis(ligand) complexes with either iron(II) or nickel(II). Infrared spectral data suggest that in these complexes the associated perchlorate or fluoroborate anions are coordinated, which leads to distorted six-coordinate structures. A similar iron(II) complex was isolated with 2,9-dimethyl-1,10-phenanthroline.

scholarly journals Anomalous Temperature Dependence of the 127I-Quadrupole Coupling in (C6H5)4PIO4, (C6H5)4AsIO4 and (C6H5)4SbIO4

1985 ◽  
Vol 40 (3) ◽  
pp. 274-278
Author(s):  
Paul K. Burkert ◽  
Dagmar G. Klobasa
Keyword(s):  
Charge Transfer ◽  
Solid State ◽  
Electric Field Gradient ◽  
Negative Pressure ◽  
Solid State Nmr ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Pressure Coefficients ◽  
Temperature Coefficients ◽  
Quadrupole Coupling

On measuring second order quadrupole effects in 127I solid state NMR, new anomalous temperature coefficients of the quadrupole interaction were observed in tetraphenylphosphonium-, tetraphenylarsonium- and tetraphenylstibonium metaperiodate. The relevance of possible mechanisms like breakdown of dπ - pπ backbonding, negative pressure coefficients, charge transfer, orientational change of the electric field gradient tensors, and influence of reorientational motions is discussed for these compounds.

Electric-Field Effects on Reactions Between Oxides

1997 ◽  
Vol 481 ◽  
Author(s):  
Matthew T. Johnson ◽  
Shelley R. Gilliss ◽  
C. Barry Carter
Keyword(s):  
Solid State ◽  
Electric Field ◽  
Elevated Temperatures ◽  
Ionic Current ◽  
Reaction Rates ◽  
Solid State Reactions ◽  
Interfacial Stability ◽  
Electric Field Effects ◽  
Thin Film Diffusion ◽  
Microscopy Techniques

ABSTRACTThin films of In2O3 and Fe2O3 have been deposited on (001) MgO using pulsed-laser deposition (PLD). These thin-film diffusion couples were then reacted in an applied electric field at elevated temperatures. In this type of solid-state reaction, both the reaction rate and the interfacial stability are affected by the transport properties of the reacting ions. The electric field provides a very large external driving force that influences the diffusion of the cations in the constitutive layers. This induced ionic current causes changes in the reaction rates, interfacial stability and distribution of the phases. Through the use of electron microscopy techniques the reaction kinetics and interface morphology have been investigated in these spinel-forming systems, to gain a better understanding of the influence of an electric field on solid-state reactions.

Anomalous Temperature Dependence in Metal–Black Phosphorus Contact

Nano Letters ◽  
2017 ◽  
Vol 18 (1) ◽  
pp. 26-31 ◽  
Author(s):  
Xuefei Li ◽  
Roberto Grassi ◽  
Sichao Li ◽  
Tiaoyang Li ◽  
Xiong Xiong ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Black Phosphorus ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature

INELASTIC NEUTRON SCATTERING IN THE ANHARMONIC MODEL OF HIGH-Tc SUPERCONDUCTORS

1990 ◽  
Vol 04 (05) ◽  
pp. 341-346 ◽  
Author(s):  
N. M. PLAKIDA ◽  
V. I. AKSENOV ◽  
S. L. DRECHSLER ◽  
T. GALBAATAR ◽  
S. STAMENKOVIC
Keyword(s):  
Neutron Scattering ◽  
Cross Sections ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Spin Model ◽  
Anomalous Temperature Dependence ◽  
High Tc Superconductors ◽  
Anomalous Temperature ◽  
High Tc ◽  
Oxygen Ions

The inelastic neutron scattering on highly anharmonic vibrations of oxygen ions in high-T c superconductors is studied in the framework of a pseudo-spin model. By evaluating the coherent and incoherent cross-sections, it is found that the scattering intensity exhibits an anomalous temperature dependence.

Anomalous temperature dependence of flow stress in a Fe3Al alloy

2000 ◽  
Vol 42 (3) ◽  
pp. 271-276 ◽  
Author(s):  
Jin-Hwa Song ◽  
Tae Kwon Ha ◽  
Young Won Chang
Keyword(s):  
Flow Stress ◽  
Temperature Dependence ◽  
Anomalous Temperature Dependence ◽  
Anomalous Temperature ◽  
Fe3al Alloy
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