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Updated: Jul 4, 2026

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
Multireference ab initio quantum mechanics/molecular mechanics study on intermediates in the catalytic cycle of
Ahmet Altun1, Devesh Kumar, Frank Neese
1Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany.
Abstract:
We have investigated the elusive reactive species of cytochrome P450(cam) (Compound I), the hydroxo complex formed during camphor hydroxylation, and the ferric hydroperoxo complex (Compound 0) by combined quantum mechanical/molecular mechanical (QM/MM) calculations, employing both density functional theory (DFT) and correlated ab initio methods. The first two intermediates appear multiconfigurational in character, especially in the doublet state and less so in the quartet state. DFT(B3LYP)/MM calculations reproduce the relative energies from correlated ab initio QM/MM treatments quite well, except for the splitting of the lowest A(1u)-A(2u) radical states. The inclusion of dynamic correlation is crucial for the proper ab initio treatment of these intermediates.
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