  Supramolecular assemblies have gained tremendous attention due to their
apparent ability to catalyze reactions with the efficiencies of natural
enzymes. Using Born-Oppenheimer molecular dynamics and density functional
theory, we identify the origin of the catalytic power of the supramolecular
assembly Ga$_4$L$_{612-}$ on the reductive elimination reaction from gold
complexes and their similarity to enzymes. By comparing the catalyzed and
uncatalyzed reaction in explicit solvent to identify the reaction free energies
of the reactants, transition states, and products, we determine that a
catalytic moiety -- an encapsulated water molecule -- generates electric fields
that contribute significant reduction in the activation free energy. Although
this is unlike the biomimetic scenario of catalysis through direct host-guest
interactions, the nanocage host preconditions the transition state for greater
sensitivity to electric field projections onto the breaking carbon bonds to
complete the reductive elimination reaction with greater catalytic efficiency.
However it is also shown that the nanocage poorly organizes the interfacial
water, which in turn creates electric fields that misalign with the breaking
bonds of the substrate, thus identifying new opportunities for catalytic design
improvements in nanocage assemblies.
