Small Molecule Activations with Self-Assembled Polynuclear
Polymetallic catalysis involving two or more metal centers can be classified amongst three broad categories: i) inorganic alloys or oxides typically containing two metals; ii) two-component systems wherein two catalysts carry out unique roles in a transformation; and iii) multinuclear complexes which contain two or more metal sites within a given coordination compound. Polynuclear designs have long been recognized to offer unique advantages over mononuclear variants for certain transformations: For mechanisms wherein multiple oxidative addition or reductive elimination steps must occur, polynuclear systems provide redox leveling, and provide additional coordination sites. Many small molecule activations may
proceed via unfavorable pathways if a suitable catalyst isn’t present. Coordinationdriven self-assembly offers a novel route to construct cofacial and related multicentered catalysts. The key to this strategy is the selection of complementary building blocks spanning Lewis-acid acceptors and basic donors with controllable orientations. This approach has the potential to greatly ease the synthesis of new catalysts with multiple, proximal active sites since each component can be prepared
independently and then unified via self-assembly reactions which typically furnish thermodynamic products in high yields. This talk will focus on the self-assembly of cofacial electrocatalysts for oxygen reduction reactions of relevance to fuel cells with an emphasis on improving the selectivity and kinetics of porphyrin-based designs.