Well-defined, bimetallic molecular clefts: A new approach to nitrogen fixation and transformation

This project concerned the use of recently prepared macrocyclic frameworks as supports for new transition metal chemistry, particularly that surrounding the catalysis of small molecules such as dinitrogen. The unique aspect of these systems is that the compounds fold upon addition of the metal cations into Pacman-like clefts, a topology that organizes both the metal-metal separation and the primary coordination sphere. While we were not successful in the immediate aims of the fixation of nitrogen, we discovered that cobalt compounds reacted with oxygen to form oxygen adducts, which were the first of this type to be crystallization and the electronic structure determined (Angew. Chem.). We also studied these compounds as oxygen reduction catalysts, a reaction integral to the efficient operation of fuel cells (Inorg. Chem.), extended the synthetic protocols to a large variety of transition metals (Chem. Eur. J), and prepared the first examples of early transition metals Pacman complexes of these macrocyclic supports (Inorg. Chim. Acta). The scope of this work has been expanded to chemistry across the Periodic Table, in particular concerning the f-elements and redox catalysis.