Thiohydroxamato complexes of iron(III). Synthesis, magnetism and Mössbauer spectra

1977 ◽  
Vol 30 (11) ◽  
pp. 2439 ◽  
Author(s):  
AJ Mitchell ◽  
KS Murray ◽  
PJ Newman ◽  
PE Clark
Keyword(s):  
High Spin ◽  
Low Temperatures ◽  
Iron Transport ◽  
Spin Crossover ◽  
Variable Temperature ◽  
Transport Systems ◽  
Spectral Measurements ◽  
Physical Measurements ◽  
Mössbauer Measurements ◽  
High Spin Iron

The syntheses of thiohydroxamic acid ligands and their iron(III) complexes are described in detail. The tris-chelates are of particular importance because of their relation to one such complex which is thought to be involved in bacterial iron-transport systems. Magnetic and spectral measurements show that the tris-chelates generally display high-spin behaviour similar to that exhibited by corresponding hydroxamato complexes. Variable temperature magnetic and Mossbauer measurements on samples of the tris(benzothiohydroxamato) derivative confirm earlier postulates of spin-crossover behaviour for this compound, with a low-spin (S 1/2 or 3/2) component at low temperatures of c. 8%. Efforts to obtain crystal structures on a tris(thiohydroxamato)iron(III) complex have been thwarted by twinning effects and by powder-like formation within well formed crystal faces. The molecular structure of these, and of the related cobalt(III) chelates, most likely contains the cis (facial) isomer. ��� A new series of bis-chelates, FeL2Cl, has also been prepared and physical measurements show high-spin iron(III) behaviour.

Coordination of Pyridine-Substituted Pyrazoles and Their Influence on the Spin State of Iron(II)

1988 ◽  
Vol 41 (11) ◽  
pp. 1645 ◽  
Author(s):  
KH Sugiyarto ◽  
HA Goodwin
Keyword(s):  
Hydrogen Bonding ◽  
Cooling Rate ◽  
High Spin ◽  
Low Temperatures ◽  
Singlet State ◽  
Variable Temperature ◽  
Spin Transition ◽  
Spectral Studies ◽  
Quintet State ◽  
Substituted Pyrazoles

Iron(II) and nickel(II) [MN6]X2 type complexes have been prepared from 2-(pyrazol-1-yl]pyridine (1pp), 2-(pyrazol-1-yl) imidazoline (pi), 2- (pyrazol-3-yl)pyridine (3pp) and 2,6-bis(pyrazol-3-yl)pyridine ( bpp ). Variable-temperature magnetic and Mossbauer spectral studies establish that [Fe(1pp)3]X2 is low spin and [Fe(pi)3]X2 is high spin over an extended temperature range, while both [Fe(3pp)3]X2 and [Fe( bpp )2]X2 undergo temperature-induced low-spin ↔ high-spin transitions. The nature of the transition depends on the extent of hydration and for salts of both cations the singlet state is generally stabilized as the extent of hydration increases. Hydrogen bonding effects are believed to be responsible for this. For anhydrous [Fe( bpp )2] [BF4]2 the transition is discontinuous and associated with hysteresis with Tc ↓ 173 K for decreasing temperature and Tc ↑ 183 K for increasing temperatures. The transition to the singlet state species is complete at low temperatures provided that the cooling rate is relatively slow. Rapid cooling to 77 K results in the trapping of a fraction of metastable quintet state species. For all other species containing either [Fe(3pp)3]2+ or [Fe( bpp )2]2+ the spin transition is continuous. Spectral data for [NiN6]X2 complexes establish an order of field strengths for the ligands pi < 3pp < 1pp < bpp , which, for the bidentate species only, is consistent with the observed electronic properties of the corresponding [FeN6]X2 complexes.

Six-coordinate high-spin iron(ii) complexes with bidentate PN ligands based on 2-aminopyridine – new Fe(ii) spin crossover systems

2014 ◽  
Vol 43 (29) ◽  
pp. 11152-11164 ◽  
Author(s):  
Christian Holzhacker ◽  
Maria José Calhorda ◽  
Adrià Gil ◽  
Maria Deus Carvalho ◽  
Liliana P. Ferreira ◽  
...  
Keyword(s):  
High Spin ◽  
Spin Crossover ◽  
High Spin Iron

Octahedral 18e iron(ii) complexes of the type [Fe(PNR-Ph)2X2] are prepared and characterized.

scholarly journals Spin-crossover and high-spin iron(ii) complexes as chemical shift19F magnetic resonance thermometers

2017 ◽  
Vol 8 (3) ◽  
pp. 2448-2456 ◽  
Author(s):  
Agnes E. Thorarinsdottir ◽  
Alexandra I. Gaudette ◽  
T. David Harris
Keyword(s):  
Magnetic Resonance ◽  
Chemical Shift ◽  
Transition Metal ◽  
Metal Complexes ◽  
High Spin ◽  
Transition Metal Complexes ◽  
Spin Crossover ◽  
Potential Utility ◽  
High Spin Iron

The potential utility of paramagnetic transition metal complexes as chemical shift19F magnetic resonance (MR) thermometers is demonstrated.

Spin Crossover during β-Hydride Elimination in High-Spin Iron(II)– and Cobalt(II)–Alkyl Complexes

2013 ◽  
Vol 32 (17) ◽  
pp. 4741-4751 ◽  
Author(s):  
Sarina M. Bellows ◽  
Thomas R. Cundari ◽  
Patrick L. Holland
Keyword(s):  
High Spin ◽  
Spin Crossover ◽  
Alkyl Complexes ◽  
Hydride Elimination ◽  
High Spin Iron

scholarly journals Anion Influence on Spin State in Two Novel Fe(III) Compounds: [Fe(5F-sal2333)]X

Crystals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 19 ◽  
Author(s):  
Sriram Sundaresan ◽  
Irina Kühne ◽  
Conor Kelly ◽  
Andrew Barker ◽  
Daniel Salley ◽  
...  
Keyword(s):  
High Spin ◽  
Spin State ◽  
Spin Crossover ◽  
Structural Investigation ◽  
Variable Temperature ◽  
Magnetic Data ◽  
Crystallographic Site ◽  
Hydrogen Atoms ◽  
High Spin Complex ◽  
Spin Complex

Structural and magnetic data on two iron (III) complexes with a hexadentate Schiff base chelating ligand and Cl− or BPh4− counterions are reported. In the solid state, the Cl− complex [Fe(5F-sal2333)]Cl, 1, is high spin between 5–300 K while the BPh4− analogue [Fe(5F-sal2333)]BPh4, 2, is low spin between 5–250 K, with onset of a gradual and incomplete spin crossover on warming to room temperature. Structural investigation reveals different orientations of the hydrogen atoms on the secondary amine donors in the two salts of the [Fe(5F-sal2333)]+ cation: high spin complex [Fe(5F-sal2333)]Cl, 1, crystallizes with non-meso orientations while the spin crossover complex [Fe(5F-sal2333)]BPh4, 2, crystallizes with a combination of meso and non-meso orientations disordered over one crystallographic site. Variable temperature electronic absorption spectroscopy of methanolic solutions of 1 and 2 suggests that both are capable of spin state switching in the solution.

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