Theoretical and Computational Chemistry

Multi and Single-Reference Methods for the Analysis of Multi-State Peroxidation of Enolates

Abstract

In spite of being spin-forbidden, some enzymes are capable of catalyzing the incorporation of O2 (3Σg) to
organic substrates without needing any cofactor. It has been established that the process followed by these
enzymes starts with the deprotonation of the substrate forming an enolate. In a second stage, the peroxidation
of the enolate formation occurs, a process in which the system changes its spin multiplicity from a triplet state
to a singlet state. In this article, we study the addition of O2 to enolates using state-of-the-art multi-reference
and single-reference methods. Our results confirm that intersystem crossing is promoted by stabilization of
the singlet state along the reaction path. When multi-reference methods are used, large active spaces are
required, and in this situation, Semistochastic Heat-Bath Configuration Interaction (SHCI) emerges as a
powerful method to study these multi-configurational systems and is in good agreement with LCCSD(T)
when the system is well-represented by a single-configuration.

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Supplementary material

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Supplementary Information

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