We investigate the spin-forbidden transitions between electronic states of the active site of the protein rubredoxin, which is responsible for electron transfer in biological systems by changing the oxidation state of the iron center in the active site. We study the active site with the iron center in three oxidation states, Fe(II), Fe(III), and Fe(IV), using density functional theory. For each oxidation state, we focused on three lowest energy electronic states with different spin multiplicities. One-dimensional cross sections of the potential energy surfaces (PES) between the equilibrium geometries of each spin-state were calculated using PBE density functional with def2-TZVP basis set. The PES cross sections lie within a 30 kcal/mol energy window and intersect at some intermediate geometries. The minimum energy crossing point (MECP) geometries and the spin-orbit coupling for each intersection have been calculated. The probability of transition between electronic states with different spin multiplicities has been determined using Landau-Zener theory for a temperature range of 270-370K.

Spin-forbidden transitions between electronic states of the active site of rubredoxin

249th National Meeting (2015)

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