A High-pressure Iron K-Edge X-ray Absorption Spectral Study of the Spin-State Crossover in {Fe[HC(3,5-(CH₃)₂pz)₃]₂} I₂ and {Fe[HC(3,5-(CH₃)₂pz)₃]₂} (BF₄)₂

Abstract

The room temperature iron K-edge X-ray absorption near edge structure spectra of {Fe[HC(3,5-(CH3)2pz)3]2} I2 and {Fe[HC(3,5-(CH3)2pz)3]2} (BF4)2 have been measured between ambient and 88 and 94 kbar, respectively, in an opposed diamond anvil cell. The iron(II) in {Fe[HC(3,5-(CH3)2pz)3] 2}I 2undergoes the expected gradual spin-state crossover from the high-spin state to the low-spin state with increasing pressure. In contrast, the iron(II) in {Fe[HC(3,5-(CH3)2pz)3] 2}(BF4)2 remains high-spin between ambient and 78 kbar and is only transformed to the low-spin state at an applied pressure of between 78 and 94 kbar. No visible change is observed in the preedge peak in the spectra of {Fe[HC(3,5-(CH3)2pz)3] 2}I2 with increasing pressure, whereas the preedge peak in the spectra of {Fe[HC(3,5-(CH3)2pz)3] 2}(BF4)2 changes as expected for a high-spin to low-spin crossover with increasing pressure. The difference in the spin-state crossover behavior of these two complexes is likely related to the unusual behavior of {Fe[HC(3,5-(CH3)2pz)3]2} (BF4)2 upon cooling.

Department(s)

Chemistry

Keywords and Phrases

Diamond; Iron; Absorption Spectroscopy; Acceleration; Cooling; Pressure; Room Temperature; Temperature Dependence; X Ray Analysis

International Standard Serial Number (ISSN)

0020-1669

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2003 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Feb 2003

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