Title

Study of the Electronic Spin-state Crossover in {Fe[HC(3,4,5-Me3pz)₃]₂}(BF₄)₂

Abstract

The synthesis, structural, magnetic, and Mössbauer spectroscopic properties of {Fe[HC(3,4,5-Me3pz)3]2}(BF4)2 are reported. The single-crystal X-ray structure results indicate that at 150 K {Fe[HC(3,4,5-Me3pz)3]2}(BF4)2 has a structure which is very similar to that observed at 220 K for the trigonally distorted octahedral, high-spin {Fe[HC(3,5-Me2pz)3]2}(BF4)2 complex. Both the magnetic and Mössbauer spectroscopic results indicate that {Fe[HC(3,4,5-Me3pz)3]2}(BF4)2 is high spin between 160 and 296 K. Upon cooling, {Fe[HC(3,4,5-Me3pz)3]2}(BF4)2 exhibits a complete electronic spin-state crossover from the high-spin to the low-spin state at approximately 110 K and remains completely low spin down to 4.2 K; upon subsequent warming from 4.2 K, the transition from the low-spin to the high-spin state occurs at 148 to 150 K. {Fe[HC(3,4,5-Me3pz)3]2}(BF4)2 exhibits a rather large thermal hysteresis of 38 K in its spin-state crossover. Thus, {Fe[HC(3,4,5-Me3pz)3]2}(BF4)2 behaves differently from both {Fe[HC(3,5-Me2pz)3]2}(BF4)2, which is known to show a unique spin-state crossover of one-half of its iron(II) ions associated with a phase transition, and Fe[HB(3,4,5-Me3pz)3]2, which is known to remain high-spin even upon cooling to 1.7 K. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Department(s)

Chemistry

Sponsor(s)

National Science Foundation of Belgium
Ministere de la Region Wallonne
National Science Foundation (U.S.)

Library of Congress Subject Headings

Iron
Mössbauer spectroscopy

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2004 John Wiley & Sons, All rights reserved.


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