Electronic structure of Fe(II)-porphyrins is of the great importance to the chemistry of hemeproteins and porphyrins-based materials.<sup> </sup>Fe(II)-porphyrins are characterized by a high density of the dark low-lying electronic states with different spin multiplicities lying below the bright Gouterman states. These dark states are involved in very complex photorelaxation mechanisms of hemeproteins. We explore the electronic structure of a series of Fe(II)-porphyrins with different first coordination spheres of Fe(II) and distorted porphyrin conformations. In particular, we are interested in the roles of electronic states with different spin multiplicities in the ultrafast photolysis of the methionine axial residue from the active site of cytochrome c. A detailed understanding of this photolysis mechanism requires high-level <i>ab initio</i> electronic structure calculations combined with the nonadiabatic kinetics or molecular dynamics modeling. We will discuss the nature of the excited states in the series of Fe(II)-porphyrins from a simple heme to complex active site models of hemeproteins.

Electronic and molecular structure of Fe(II)-porphyrins

ACS Spring 2022

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