A Density Functional Calculation of the Electric Properties of Several High-Spin and Low-Spin Iron(II) Pyrazolylborate Complexes
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.
F. Remacle et al., "A Density Functional Calculation of the Electric Properties of Several High-Spin and Low-Spin Iron(II) Pyrazolylborate Complexes," Inorganic Chemistry, vol. 47, no. 10, pp. 4005-4014, American Chemical Society (ACS), May 2008.
The definitive version is available at https://doi.org/10.1021/ic701367b
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