Nature confines metalloenzyme active sites within well-defined pockets to protect high energy intermediates from deleterious off-cycle reactivity. Hydrophobic channels connecting these sites to the exterior environment can provide routes for substrate ingress and product egress. Inspired by these design principles, our group has constructed a ligand platform that orients a rigid and narrow organic macrocycle atop a metal coordination site. We have shown that this macrocycle can gate access of exogenous reactants to the coordination sphere. This talk will focus on our recent successes in stabilizing and characterizing high-valent iron oxo species by confining the FeO unit within the macrocycle. Notably, confinement can yield a high-spin ferryl oxo complex that is indefinitely stable at ambient temperatures, allowing for physical property measurements and reactivity studies that are impossible or impractical using other S = 2 ferryl oxo species.1