Developing a Generalized Model for Compartmentalization of Organometallic Catalysis

Compartments can improve the efficiency of cascade reactions through retainment of ephemeral intermediates by minimizing competing elimination pathways. Numerous examples of compartments exist in biocatalysis, one such example being oxygen sensitive nitrogenases in microbes, where the enzyme is spatially located in an anaerobic domain to prevent deactivation. Recently, extensive efforts have been devoted to developing models and guiding design principles for compartmentalization of biocatalytic cascades. However, little to no effort has been devoted to analyzing compartmentalization of organometallic catalytic cycles from a theoretical perspective, which reasonably may benefit from compartmentalization given their numerous, common deactivation pathways. Herein, we develop a mathematical model for compartmentalization of a general three step organometallic catalytic cycle operating within a nanowire array electrode as an example nanostructure. Under the same kinetic parameters, the model predicts that compartmentalization enhances key reaction metrics, being intermediate elimination/outflux, reaction conversion, and turnover frequency in comparison to a non-compartmentalized cycle. We show that tuning mass transport through variation of nanostructure geometry is a viable approach to optimizing the turnover of a solution cascade reaction. Furthermore, we demonstrate that elimination reactions occurring outside of the compartment establish a concentration gradient that with feasible diffusive conductance, augments intermediate outflux. We posit that a well designed nanostructure will circumvent this issue even with fast eliminations. The model serves as a starting point and may be adapted to suit any organometallic catalytic cycle and nanostructure geometry.