Hybrid computational chemistry techniques such as QM/MM have great potential for elucidating the chemical reaction mechanisms of complex molecular systems such as metalloenzymes and metal-organic frameworks. Hybrid approaches are also useful for studying, e.g., transition-metal catalyzed organic reactions especially when the catalysts contain bulky ligands. Therefore, we are applying hybrid QM/MM and QM/QM approaches to a broad range of complex molecular systems, with the aim of learning the factors that tip the balance of reactivity or selectivity. For example, we have recently studied the reaction of aromatase, a sort of cytochrome P450 enzyme pertaining to breast cancer, and Fe-MOF-74, a metal-organic framework that effects chemically difficult C–H bond activation probably via the formation of an oxoiron(IV) species, which is reminiscent of the compound I active species of cytochrome P450 enzymes. Indeed, these QM/MM studies provided valuable insights into the rapid reaction steps involved. On the technical side, if we intend to study many different types of molecules using QM/MM, it becomes difficult to apply a single transferrable force field for the calculations of MM energies, because oftentimes users encounter cases in which some necessary force-field parameters are unavailable; we are trying to address this issue via a simple approach.

Studies of chemical reactions of organic molecules, enzymes, and metal-organic frameworks by means of QM/MM and QM/QM computational approaches

252nd National Meeting (2016)

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