Metal-Complexes of 1,10-Phenanthroline Derivatives. XV. Complexes of 2-(3,5-Dimethylpyrazol-1-yl)-1,10-phenanthroline

1988 ◽  
Vol 41 (6) ◽  
pp. 873 ◽  
Author(s):  
AS Abushamleh ◽  
HA Goodwin
Keyword(s):  
Magnetic Properties ◽  
Solid State ◽  
Spectral Data ◽  
High Spin ◽  
Nickel Complex ◽  
Spin Transition ◽  
Critical Value ◽  
Magnetic Data ◽  
Strong Temperature Dependence ◽  
Thermally Induced

Iron(II) and nickel(II) bis ( ligand ) complexes of 2-(3,5-dimethylpyrazol-1-yl)-1,10-phenanthroline (L) have been prepared. The field strength of L as determined from spectral data for the nickel complex is in the range encompassing the critical value at the singlet (1A1) ↔ quintet (5T2) crossover for iron(II). The magnetic properties of the iron(II) complex both in solution and in the solid state are anomalous, and indicative of the occurrence of a thermally induced spin transition. Mossbauer spectral data confirm this, and reveal separate contributions from the singlet and quintet species with a strong temperature-dependence of their relative intensities. Magnetic data for the complex in solution are consistent with a simple high spin ↔ low spin equilibrium, and lead to values of ΔH = 23�0.5 kJ mol-1 and ΔS = 66�5 J K-1 mol-1 for the low spin → high spin transformation.

Iron(II) and Nickel(II) Complexes of 2,6-Di(thiazol-2-yl)pyridine and Related Ligands

1991 ◽  
Vol 44 (8) ◽  
pp. 1041 ◽  
Author(s):  
AT Baker ◽  
P Singh ◽  
V Vignevich
Keyword(s):  
High Spin ◽  
Room Temperature ◽  
Spin Transition ◽  
Magnetic Behaviour ◽  
Diethyl Acetal ◽  
Thermally Induced ◽  
Field Strengths

2,6-Di(thiazol-2-yl]pyridine (1a), 2,6-di(4-methylthiazol-2-yl)pyridine (1b) and 2,6-di(2-imid-azolin-2-yl)pyridine (3) have been prepared by the reaction of pyridine-2,6-dicarbothioamide with bromoacetaldehyde diethyl acetal, bromoacetone and ethylenediamine, severally. Bis ( ligand ) iron(II) and nickel(II) complexes of all ligands have been prepared. The bis ( ligand ) iron(II) complexes of (1a) and (3) are low-spin whereas that of (1b) is high-spin at room temperature and undergoes a thermally induced spin transition. The field strengths of the ligands , determined from the spectra of their nickel(II) complexes, correlate well with the observed magnetic behaviour of their iron(II) complexes. The field strengths of (1a) and (1b) are found to be marginally less than those of the isomeric ligands 2,6-di(thiazol-4-yl)pyridine (2a) and 2,6-di(2-methylthiazol-4-yl)pyridine (2b).

Optical Microscopy Imaging of the Thermally-Induced Spin Transition and Isothermal Multi-stepped Relaxation in a Low-Spin Stabilized Spin-Crossover Material

2021 ◽  
Author(s):  
Pradip Chakraborty ◽  
Mouhamadou Sy ◽  
Houcem Fourati ◽  
Maria Teresa Delgado Pérez ◽  
Mousumi Dutta ◽  
...  
Keyword(s):  
Optical Microscopy ◽  
High Spin ◽  
Spin Relaxation ◽  
Spin Crossover ◽  
Spin Transition ◽  
Host Lattice ◽  
Microscopy Imaging ◽  
Thermally Induced ◽  
Optical Microscopy Imaging

The thermal spin transition and the photo-induced high-spin → low-spin relaxation of the prototypical [Fe(ptz)6](BF4)2 spin-crossover compound (ptz = 1-propyltetrazole) diluted in the isostructural ruthenium host lattice [Ru(ptz)6](BF4)2, which stabilizes...

Iron complexes of pyridylimidazole derivatives

1977 ◽  
Vol 30 (4) ◽  
pp. 771 ◽  
Author(s):  
AT Baker ◽  
HA Goodwin
Keyword(s):  
Charge Transfer ◽  
Spectral Data ◽  
High Spin ◽  
Mössbauer Effect ◽  
Spin Transition ◽  
Iron Complexes ◽  
Mossbauer Effect ◽  
Effect Data ◽  
Electronic Spectral Data

Complexes of iron(II) with 2-(2-pyridyl)benzimidazole (pbi) and 2-(6- methyl-2-pyridyl)benzimidazole (mpbi) have been characterized. [Fe(pbi)3] [BF4]2 undergoes a temperature-induced spin transition the course of which is determined by the extent of hydration. [Fe(mpbi)3] [ClO4]2 is high-spin and the differences in the properties of the two complexes are correlated with electronic spectral data. [Fe(pbi)2(CN)2] is low-spin. Iron(III) complexes of deprotonated pbi and 2-(2- pyridyl)imidazole (pyim), [Fe(pbi-H)3] and [Fe(pyim-H)3], result when the cationic iron(II) complexes are treated with base. Magnetic and Mossbauer effect data show that these complexes, which display strong π → t2 charge-transfer absorption, are low-spin.

The singlet-quintet transition in Tris[2-(pyridin-2-yl)benzothiazole]iron(II) Bis(tetraphenylborate)

1984 ◽  
Vol 37 (6) ◽  
pp. 1157 ◽  
Author(s):  
AT Baker ◽  
HA Goodwin
Keyword(s):  
Field Strength ◽  
Spectral Data ◽  
Magnetic Moment ◽  
Spin Transition ◽  
Empirical Treatment ◽  
Temperature Dependent ◽  
Thermally Induced ◽  
Thiazole Derivative

The tris[2-(pyridin-2-yl)benzothiazole]iron(II) ion has been isolated as the tetraphenylborate salt which is stable in the atmosphere for short periods. The deep red complex displays a temperature-dependent magnetic moment and thermochroism which are associated with a thermally induced singlet (1A1) ↔ quintet (5T2) spin transition. An empirical treatment of the transition, which is continuous, yields ∆H and ∆S values of 22.7 kJ mol-1 and 91 JK-1 mol-1 over the range 275-364 K. Spectral data for the corresponding nickel(11) complex confirm the intermediate nature of the field strength of the benzothiazole and indicate that it is a weaker ligand than the corresponding thiazole derivative.

Structural Changes in Iron(II) Polymeric Complexes upon Thermally and Optically Induced Spin Transition Determined by EXAFS Spectroscopy

1998 ◽  
Vol 524 ◽  
Author(s):  
S. B. Erenburg ◽  
N. V. Bausk ◽  
L. G. Lavrenova ◽  
Yu. G. Shvedenkov ◽  
L. N. Mazalov
Keyword(s):  
High Spin ◽  
Structural Changes ◽  
Mutual Influence ◽  
Chemical Shifts ◽  
Spin Transition ◽  
High Spin State ◽  
Local Environment ◽  
Thermally Induced ◽  
Polymeric Complexes ◽  
Electronic And Spatial Structure

ABSTRACTChanges in the electronic and spatial structure of polymeric Fe(II) complexes with 1,2,4- triazoles and various anions upon spin transition was studied using EXAFS and XANES spectroscopy. Spin transition and structural changes were induced by variations of the anion, dilution with Zn, under heating or the action of light. In all complexes, the spin transition is accompanied by drastic changes in the local environment of Fe atoms. The increase in spin transition temperature for the complexes with variable anions CIO4-, I-, Br-, BF4-, NO3- was found to correlate with changes in the Fe-N distances and changes in bond covalence determined from the chemical shifts in Mössbauer spectra. High spin metastable long life states were detected and studied in the polymeric complex Fe(atrz)3(ClO4)2. It was established that the changes in structure of polymeric complexes upon the transition to a metastable high spin state under the action of light differ from those in the thermally induced spin transition. Such differences are determined by mutual influence of Fe atoms in high spin and low spin states in polymeric chains.

Demonstration of the thermally induced high spin–low spin transition for a transparent spin crossover complex film [Fe(II)(H-trz)3]-Nafion (trz=triazole)

Polyhedron ◽  
2005 ◽  
Vol 24 (16-17) ◽  
pp. 2909-2912 ◽  
Author(s):  
Akio Nakamoto ◽  
Norimichi Kojima ◽  
Liu XiaoJun ◽  
Yutaka Moritomo ◽  
Arao Nakamura
Keyword(s):  
High Spin ◽  
Spin Crossover ◽  
Spin Transition ◽  
Thermally Induced ◽  
Complex Film

scholarly journals The Effect of Pressure on Magnetic Properties of Prussian Blue Analogues

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 112 ◽  
Author(s):  
Maria Zentkova ◽  
Marian Mihalik
Keyword(s):  
Crystal Structure ◽  
Magnetic Properties ◽  
Curie Temperature ◽  
Prussian Blue ◽  
High Spin ◽  
Pressure Effect ◽  
Spin Transition ◽  
Applied Pressure ◽  
Effect Of Pressure ◽  
Prussian Blue Analogues

We present the review of pressure effect on the crystal structure and magnetic properties of Cr(CN)6-based Prussian blue analogues (PBs). The lattice volume of the fcc crystal structure space group Fm 3 ¯ m in the Mn-Cr-CN-PBs linearly decreases for p ≤ 1.7 GPa, the change of lattice size levels off at 3.2 GPa, and above 4.2 GPa an amorphous-like structure appears. The crystal structure recovers after removal of pressure as high as 4.5 GPa. The effect of pressure on magnetic properties follows the non-monotonous pressure dependence of the crystal lattice. The amorphous like structure is accompanied with reduction of the Curie temperature (TC) to zero and a corresponding collapse of the ferrimagnetic moment at 10 GPa. The cell volume of Ni-Cr-CN-PBs decreases linearly and is isotropic in the range of 0–3.1 GPa. The Raman spectra can indicate a weak linkage isomerisation induced by pressure. The Curie temperature in Mn2+-CrIII-PBs and Cr2+-CrIII-PBs with dominant antiferromagnetic super-exchange interaction increases with pressure in comparison with decrease of TC in Ni2+-CrIII-PBs and Co2+-CrIII-PBs ferromagnets. TC increases with increasing pressure for ferrimagnetic systems due to the strengthening of magnetic interaction because pressure, which enlarges the monoelectronic overlap integral S and energy gap ∆ between the mixed molecular orbitals. The reduction of bonding angles between magnetic ions connected by the CN group leads to a small decrease of magnetic coupling. Such a reduction can be expected on both compounds with ferromagnetic and ferrimagnetic ordering. In the second case this effect is masked by the increase of coupling caused by the enlarged overlap between magnetic orbitals. In the case of mixed ferro–ferromagnetic systems, pressure affects μ(T) by a different method in Mn2+–N≡C–CrIII subsystem and CrIII–C≡N–Ni2+ subsystem, and as a consequence Tcomp decreases when the pressure is applied. The pressure changes magnetization processes in both systems, but we expect that spontaneous magnetization is not affected in Mn2+-CrIII-PBs, Ni2+-CrIII-PBs, and Co2+-CrIII-PBs. Pressure-induced magnetic hardening is attributed to a change in magneto-crystalline anisotropy induced by pressure. The applied pressure reduces saturated magnetization of Cr2+-CrIII-PBs. The applied pressure p = 0.84 GPa induces high spin–low spin transition of cca 4.5% of high spin Cr2+. The pressure effect on magnetic properties of PBs nano powders and core–shell heterostructures follows tendencies known from bulk parent PBs.

The complexes of iminodiacetic acid with divalent manganese and iron

1982 ◽  
Vol 47 (4) ◽  
pp. 1169-1175 ◽  
Author(s):  
Ivan Lukeš ◽  
Ivana Šmídová ◽  
Miroslav Ebert
Keyword(s):  
Thermal Stability ◽  
Magnetic Properties ◽  
Solid State ◽  
High Spin ◽  
Infrared Spectra ◽  
Iminodiacetic Acid ◽  
Octahedral Configuration

Complexes of the type M2[Me(IDA)2] and MeIDA.n H2O, where M = H+, Li+, Na+, K+, 1/2 Ba2+, Me = Mn2+, Fe2+ and IDA = [NH(CH2COO)2]2- were prepared in the solid state. The magnetic properties, thermal stability and electron and infrared spectra of these substances were studied. It followed from the results that both prepared types of complex have a high spin octahedral configuration. In contrast to M2[Me(IDA)2] type complexes, complexes of the Me IDA . nH2O type have polymeric character.

Thermally Induced High-Spin Low-Spin Transition in Co[Cr0.5Ga1.5]S4 Spinel

2011 ◽  
Vol 170 ◽  
pp. 9-12
Author(s):  
J. Krok-Kowalski ◽  
Ewa Maciążek ◽  
Tadeusz Groń ◽  
Andrzej W. Pacyna ◽  
Tadeusz Mydlarz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
High Spin ◽  
Inflection Point ◽  
Spin Transition ◽  
Spin Frustration ◽  
Strong Suppression ◽  
Thermally Induced ◽  
Tetrahedral Sites ◽  
Curie Temperature Tc

A high spin (HS) – low spin (LS) transition has been discovered in the Co[Cr0.5Ga1.5]S4 spinel, where the Co ions occupy tetrahedral sites and the Cr and Ga ions octahedral ones. The latter are diluted by the non-magnetic Ga-ions. Application of magnetic fields revealed ferrimagnetic order with a Curie temperature TC = 126 K, a strong suppression of the magnetic susceptibility () and a slight shift of TC to lower temperatures. A cusp at 15.6 K on the ac (T) curve suggests a spin frustration of the re-entrant type. Characteristic for the HS-LS transition is an inflection point at 150 K on the 1/(T) curve, a lack of the Curie-Weiss region above TC and a small value of the magnetization, 4.76 emu/g at 4.4 K and at a magnetic field of 57.5 kOe.

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