High-spin .dblharw. low-spin transition in hexacoordinate complexes of iron(II) with monodentate 1-alkyltetrazole ligands: a variable-temperature Moessbauer, magnetic susceptibility, and far-infrared study

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.

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Direct Observation of Fine Structure Transitions in a Paramagnetic Nickel(II) Complex Using Far-Infrared Magnetic Spectroscopy: A New Method for Studying High-Spin Transition Metal Complexes

Inorganic Chemistry ◽

10.1021/ic030013o ◽

2003 ◽

Vol 42 (6) ◽

pp. 1788-1790 ◽

Cited By ~ 37

Author(s):

Suriyakan Vongtragool ◽

Boris Gorshunov ◽

Martin Dressel ◽

J. Krzystek ◽

David M. Eichhorn ◽

...

Keyword(s):

Fine Structure ◽

Transition Metal ◽

Metal Complexes ◽

High Spin ◽

Transition Metal Complexes ◽

Direct Observation ◽

Spin Transition ◽

Far Infrared ◽

New Method

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Preparation, electrochemical behavior, and variable-temperature magnetic properties of Co(3,5-DBSQ)2 complexes of imidazole- or pyrazole-substituted ligands

Canadian Journal of Chemistry ◽

10.1139/cjc-2014-0583 ◽

2015 ◽

Vol 93 (7) ◽

pp. 769-774 ◽

Cited By ~ 1

Author(s):

Carolyn Dowling ◽

Danielle R. Dinsdale ◽

Martin T. Lemaire

Keyword(s):

Magnetic Susceptibility ◽

High Spin ◽

Density Functional ◽

Variable Temperature ◽

Density Functional Theory Calculations ◽

Functional Theory ◽

Magnetic Susceptibility Data ◽

Valence Tautomerism ◽

Susceptibility Data ◽

Variable Temperature Magnetic Susceptibility

Herein we describe the preparation of four new Co(3,5-DBSQ)2 containing known 2-(2-pyridyl)benzimidazole 1, 2,2′-bisbenzimidazole 2, or 2,2-(1H-pyrazole-3,5-diyl)dipyridine 3. We investigate the electronic and variable-temperature magnetic susceptibility properties of these complexes. Complexes containing 2 and 3 are bimetallic and variable-temperature magnetic susceptibility data suggest observation of a stable intermediate (high-spin and low-spin) state for the bimetallic complex with 3, which does undergo valence tautomerism. Complexes 4–6 containing imidazole-based ligands 1 and 2 feature high-spin ground states and no valence tautomerism is observed in these materials. This experimental finding is corroborated with density functional theory calculations, which support the existence of a stable high-spin ground state in these complexes.

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

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.170.9 ◽

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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Evidence for high-spin-to-low-spin transition under pressure in Fe 72 Pt 28 Invar alloy

Philosophical Magazine B ◽

10.1080/014186300255573 ◽

2000 ◽

Vol 80 (2) ◽

pp. 155-163 ◽

Cited By ~ 2

Author(s):

S. Odin, F. Baudelet, E. Dartyge, J. P

Keyword(s):

High Spin ◽

Spin Transition ◽

Invar Alloy

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