Electronic ground states of low-spin iron(III) porphyrinoids

Nakamura, Mikio; Ohgo, Yoshiaki; Ikezaki, Akira

doi:10.1016/j.jinorgbio.2007.10.024

Cited by 37 publications

(27 citation statements)

References 48 publications

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“…In particular, first-row metal ions, such as Cr n+ , Mn n+ , Fe n+ , and Co n+ , adopt a variety of electronic structures, including high-spin, low-spin, and in some cases intermediate-spin states. [1] Furthermore, each spin state could have different electron configurations, as exemplified most explicitly in low-spin iron(III) porphyrins; they adopt either (d xy ) 2 [2] In octahedral complexes, strong-field ligands increase the magnitude of ligand field splitting (D o ) to the point that is larger than the electron pairing energy (PE). Consequently, they form low-spin complexes.…”

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“…[1] Furthermore, each spin state could have different electron configurations, as exemplified most explicitly in low-spin iron(III) porphyrins; they adopt either (d xy ) 2 (d xz ,d yz ) 3 or (d xz ,d yz ) 4 (d xy ) 1 configurations. [2] In octahedral complexes, strong-field ligands increase the magnitude of ligand field splitting (D o ) to the point that is larger than the electron pairing energy (PE). Consequently, they form low-spin complexes.…”

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Is Cyanide Really a Strong‐Field Ligand?

Nakamura

2009

Angew Chem Int Ed

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Is Cyanide Really a Strong‐Field Ligand?

Nakamura

2009

Angew Chem Int Ed

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“…Heme functions are highly sensitive to changes in the macrocycle because of its high flexibility , . Some earlier studies showed that the porphyrin core could regulate the spin state of nickel(II) ions and the electronic ground states of low‐spin (LS) iron(III) ions, , in a porphyrin on the basis of the expansion or contraction of the core. We found that the size‐matching rule could be used to obtain a combination of variable core and alterable iron species.…”

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Optimal Size Matching and Minimal Distortion Energy: Implications for Natural Selection by the Macrocycle of the Iron Species in Heme

et al. 2016

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In heme, a porphyrin macrocycle naturally selects an iron ionic species. It was found that this natural combination is directly related to the geometry sizes of both components. Three series of monostrapped nonplanar metalloporphyrins [M = FeIIICl, CoII, NiII] and their metal‐free counterparts were synthesized as model systems, their core sizes were compared, and density functional theory computations were used to calculate the molecular distortion energies. The results indicate that optimal size matching of both is to maintain minimal distortion energy of the macrocycle. This shows that the mutual selection process between the macrocycle and the metal ion is mainly based on the principle of minimum energy to tune the electronic structure of the central metal ion; this may be a common principle in natural tetrapyrroles containing metal species. The structural parameters of all the model compounds were directly obtained from their crystal structures.

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“…The question then arises as to why there is no antiferromagnetic coupling in ruffled six-coordinate Fe(T i PrP•)(ClO 4 ) 2 in spite of the well known fact that the half-occupied iron d xy orbital can interact with the doubly occupied porphyrin a 2u orbital in low-spin iron(III) complexes with ruffled porphyrin framework [21,22,33,34]; both d xy and a 2u orbitals in planar D 4h complex are signified as b 2 in ruffled D 2d complex [35,36]. A possible explanation is that radical cationic Fe (T i PrP•)(ClO 4 ) 2 posseses no unpaired electron in the d xy orbital.…”

Section: Resultsmentioning

confidence: 99%