Figure 2.
Top: Schematic energy profile along the reaction coordinate from the IM1 Reactant state to the IM2 Product state (Mo(VI)-S to Mo(IV)-P) as a function of the C7-H (labelled in red in Figure 1) distance (Q) of substrate (4-thiolumazine). The red arrow depicts a hypothetical two-electron transition to the Frank-Condon ES, and the blue arrow depicts the instantaneous distorting force toward the minimum along the ES PES. Bottom: Simple diagram showing how two electrons are transferred from the Substrate HOMO to the Mo(xy) redox orbital along the reaction coordinate. In this two-state frontier orbital depiction, the Substrate HOMO smoothly transitions to the Product LUMO.