Spin‐State‐Dependent Properties of an Iron(III) Hydrogenase Mimic

Abstract

A biomimetic mononuclear iron(III) model complex was investigated in detail by density functional theory (DFT) calculations. Structural and energetic criteria were employed to confirm the S = 3/2 intermediate state to be the ground state. The ground state was verified by using both pure and hybrid functionals with different amounts of exact Hartree-Fock exchange. A comprehensive study of the influence of the functional as well as thermodynamic corrections to the energetic ordering of spin states was performed. A modified B3LYP functional with 10 % Hartree-Fock exchange was able to reproduce the structural properties in excellent agreement

Theoretical Study of the Iron Complexes with Aminoguanidine: Investigating Secondary Antioxidant Activity

“…It is interesting to note that the low-spin complexes always have shorter bond distances from the coordinating atoms to the central ion compared to the high-spin counterparts, especially from the water molecules. This behavior has been shown previously in computation calculations with other ligands [ 44 ].…”

Experimental and Theoretical Identification of the Origin of Magnetic Anisotropy in Intermediate Spin Iron(III) Complexes

“…In the case of Fe III (d 5 ), intermediate spin ground states are observed mainly for complexes of square pyramidal coordination geometry with few exceptions found in octahedral or square planar complexes in case of suitable ligand environments . Although the electronic and magnetic properties of a number of mononuclear S= 3/2 Fe III complexes have been the subject of detailed experimental studies, the corresponding computational studies are limited to the determination of the spin of their ground states, and, to the best of our knowledge, the present report is the first theoretical consideration of the origin of their magnetic anisotropy ,…”

Bona fide choline monoxygenases evolved in Amaranthaceae plants from oxygenases of unknown function: Evidence from phylogenetics, homology modeling and docking studies

“…(C) Results of the Rd.HMM analysis of the final So CMO2, So CMO1 and At CMO1 homology models shown per subunit. Note that in this kind of analysis a Rd-HMM index value of 0.6 is obtained for structures solved by X-ray crystallography [ 42 ]. The RMSD values given are relative to the bacterial monoxygenase (PDB: 3N0Q) used as template for modeling So CMO2 and were calculated using STAMP [ 43 ] to match equivalent positions in the structures.…”

“…Analyzing the three homology models with the Rd.HMM protocol [ 42 ] we found that, out of all sequences in the NCBI-RefSeq database, the So CMO2 amino acid sequence (XP_021849509), the At CMO1 amino acid sequence (NP_194718) and the So CMO1 amino acid sequence (XP_021866412) were the first retrieved when using the So CMO2, At CMO1 and So CMO1 homology models, respectively, indicating that the models indeed can accommodate the respective sequences better than the sequences of any other protein in the NCBI RefSeq database. The results of the validation of the homology models shown in Fig 6C indicate an appropriate backbone for all models, with a Rd.HMM index value just slightly below the value reported for X-ray crystallography determined structures [ 43 ].…”

“…To better represent the geometrical and chemical features of the mononuclear non-heme iron, a dioxygen and a water molecule were linked to it. QM calculations were done with the low-spin configuration for an oxidized Rieske [2Fe-2S] center [ 41 ], and with and intermediate number of unpaired spin electrons in the case of the Fe 3+ /O 2 /H 2 O mononuclear non-heme Fe center [ 42 ]. The validation of these topologies was performed analysing the geometrical fluctuations in short simulations (1 ns) of an isolated molecule comprising the [2Fe-2S] Rieske and its covalently linked amino acid residues, or the mononuclear non-heme Fe and its covalently linked amino acid residues.…”