DFT Calculations for Mössbauer Properties on Dinuclear Center Models of the Resting Oxidized Cytochrome c Oxidase

Mössbauer isomer shift and quadrupole splitting properties have been calculated using the OLYP‐D3(BJ) density functional method on previously obtained (W.‐G. Han Du, et al., Inorg Chem. 2020, 59, 8906–8915) geometry optimized Fe(a3) (3+)−H(2)O−Cu(B) (2+) dinuclear center (DNC) clusters of the resting oxidized (O state) “as‐isolated” cytochrome c oxidase (CcO). The calculated results are highly consistent with the available experimental observations. The calculations have also shown that the structural heterogeneities of the O state DNCs implicated by the Mössbauer experiments are likely consequences of various factors, particularly the variable positions of the central H(2)O molecule between the Fe(a3) (3+) and Cu(B) (2+) sites in different DNCs, whether or not this central H(2)O molecule has H‐bonding interaction with another H(2)O molecule, the different spin states having similar energies for the Fe(a3) (3+) sites, and whether the Fe(a3) (3+) and Cu(B) (2+) sites are ferromagnetically or antiferromagnetically spin‐coupled.