Coordination Chemistry and Electronic Structure of Iron Clusters

Abstract

Mixed valence compounds have been recognized over the past five decades as a unique class of chemical species. Their distinctive spectral, electrochemical, physical and magnetic properties arise from electron delocalization into the sites with uneven valence. A primary consequence of this electron delocalization phenomenon is the stabilization of high spin multiplicities in certain dinuclear synthetic and polynuclear biological clusters. Therefore, the subject of this dissertation is to extend the current knowledge of the analysis of synthetic mixed valence clusters by systematically altering the coordination chemistry and redox states at well-defined synthetic, polynuclear iron clusters. A central focus of this thesis is to investigate the effect of superexchange, direct exchange, and double exchange electronic coupling in dinuclear [Fe2], trinuclear [Fe3], hexanuclear [Fe6], and octanuclear [Fe8] clusters with the goal of better understanding the principles that govern their complex electronic structures. It is concluded that the resulting electronic structure in these polynuclear systems is highly dependent on the extent of electron delocalization which can be tuned by solvation, anation, or chemical redox changes. This finding is highlighted by the observation that small variations on the solvation coordination sphere and redox level one can transverse spin ground states from S = 0 to S = 11 by addition of 6e– into [Fe6].