Electrostatic Interactions in Heterobimetallic Complexes and their Effect on Reduction Potentials, Electronic Structure, and Reactivity
The use of electrostatic interactions is fundamental in the the structure and function of biological enzymes, and has the potential to be a powerful tool in synthetic complexes as well. Electric fields generated by charged species have remarkable influence over electronic structure and intermolecular reactivity, and are capable of remarkable thermodynamic control in catalysis. Herein, a heterobimetallic platform consisting of a Schiff base binding site and an enchained crown ether ring is used to show a diverse range of effects that arise when a transition metal and a cation are placed in close proximity.
In Chapter 1, spectroscopic and electrochemical techniques are used to demonstrate the role of electrostatic interactions on a nearby cobalt center. These experiments demonstrate the use of a wide range of cationic metals to impart significant shifts on the reduction potentials of a proximal transition metal center. Additionally, the role of solvent and anion coordination in the screening of electrostatic interactions are established.
In Chapter 2, further studies are conducted with a nickel analogue of this heterobimetallic framework. Theoretical calculations are used to demonstrate the effect of electrostatics on the expanded molecular orbital manifold of metal Schiff base systems.
In Chapter 3, a manganese complex is used to demonstrate the role of electrostatic interactions on reactivity. Extensive studies are carried out on the kinetic and thermodynamic considerations for the N-N coupling of Mn(V) nitrides, which showed that cationic charge is capable of stabilizing activated nitride species against bimolecular reactivity. The effect of proximal cations on ammonia oxidation and pKa are also explored.