A Density Functional Calculation of the Electric Properties of Several High-Spin and Low-Spin Iron(II) Pyrazolylborate Complexes

Abstract

Density functional theory has been used to study the electronic spin-state properties of low-spin Fe[HB(pz)3]2, high-spin Fe[HB(3-Mepz)3]2, high-spin Fe[HB(3,5-Me2pz)3]2, and high-spin Fe[HB(3,4,5-Me3pz)3]2 complexes that exhibit very different iron(II) electronic spin-sate crossover behaviors with changing temperature and pressure. Excellent agreement is obtained between the experimentally observed Mössbauer-effect quadrupole splittings and isomer shifts of these complexes and those calculated with the B3LYP functional and various different basis sets for both the high-spin and low-spin states of iron(II). The calculations for Fe[HB(pz)3]2 that use the LANL2DZ, 6-31++G(d,p), and 6-311++G(d,p) basis sets for iron all lead to very similar electric field gradients and thus quadrupole splittings. The initial calculations, which were based upon the known X-ray structures, were followed by structural optimization, an optimization that led to small increases in the Fe-N bond distances. Optimization led to at most trivial changes in the intraligand bond distances and angles. The importance of the 3-methyl-H…H-3-methyl nonbonded intramolecular interligand interactions in controlling the minimum Fe-N bond distances and determining the iron(II) spin state both in Fe[HB(3-Mepz)3]2 and in the related methyl-substituted complexes has been identified.

Department(s)

Chemistry

Sponsor(s)

National Science Foundation of Belgium
Ministere de la Region Wallonne

International Standard Serial Number (ISSN)

0020-1669

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2008 American Chemical Society (ACS), All rights reserved.

Publication Date

01 May 2008

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