This award in the Inorganic, Bioinorganic, and Organometallic program is made to Dr. Terrence J. Collins in the Chemistry Department of Carnegie Mellon University to continue work on coordination complexes containing transition metals in high oxidation states. Collins has developed macroamide ligands which are not susceptible to oxidation and can be used to maintain Mn, Fe, Co, and Ni in unusual high oxidation states. Synthesis of additional compounds of this type will be attempted. Depending on the metal and structure of the respective compound, it may serve as a model for methane monooxygenase, as an electrocatalyst or chemical sensor, a catalytic O-atom transfer agent, or exhibit antiferromagnetic coupling at low temperatures. The compounds will be characterized using a variety of techniques, including electron paramagnetic resonance and Mossbauer spectroscopies, and cyclic voltammetry. The investigation will focus on four square-planar complexes of Mn(V) that are known, as well as 5- and 6-coordinate systems. Synthesis of nitrido analogs of some known manganese and iron compounds will be attempted. Oxygen atom transfer reactions of Fe(IV), Ni(III), and Co(III) will also be investigated. The reaction chemistry of a stable Fe(IV)-O-Fe(IV) species, which is known to undergo three reversible oxidations, will be explored in detail. A detailed magnetic study will be undertaken of a linear polymer of antiferromagnetically coupled S=2 Mn(III) centers that shows unusual ferromagnetic interactions at low temperatures.
