Synthesis and Paramagnetic Resonance Spetroscopy of Homo- and Heterobinuclear Manganese Complexes
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Synthesis and characterization of homo- and hetero-binuclear manganese complexes in a clathrochelate environment were performed. The clathrochelating ligand used results from the condensation of 2 equivalents of Iris (2-aminoethyl) amine (trenH6) and 3 equivalents of 2,6-diformyl-4-methylphenol (dialH).1 The clathrochelate ligand provides an encapsulating and inflexible environment for two metal atoms. The appearance of manganese atoms in biological electron transfer roles is well known. The most biologically significant metal site involving manganese occurs in the oxygen-evolving complex (OEC) during photosynthesis of green plants and cyanobacteria.2 There are also numerous examples of manganese enzymes that contain a pair of coupled Mnll ions in their catalytic sites, such as bacterial catalases. The binuclear manganese compounds studied for this project are not intended to be a model of the PS II system or of the dimanganese catalases. Of particular interest are the electronic properties of the binuclear complexes removed from solvent interaction by the presence of the clathrochelate ligand. Preliminary EPR measurements indicate the existence of coupling between the manganese ions in the Mni"Mnll clathrochelate complex. The EPR spectrum for the MnllZnli species suggests a magnetically isolated system. The mixed-valence character of the MnilMniii complex is undetermined as of yet.