Synthesis, structural studies, and oxidation catalysis of the manganese(II), iron(II), and copper(II) complexes of a 2-pyridylmethyl pendant armed side-bridged cyclam.

The first 2-pyridylmethyl pendant armed structurally reinforced cyclam ligand has been synthesized and successfully complexed to Mn, Fe, and Cu cations. X-ray crystal structures were obtained for the diprotonated ligand and its Cu complex demonstrating pentadentate binding of the ligand with configuration of the side-bridged cyclam ring, leaving a potential labile binding site to the pyridine donor for interaction of the complex with oxidants and/or substrates. The electronic properties of these complexes were determined by means of solid state magnetic moment, with a low value of μ = 3.10 μ for the Fe complex suggesting it has a trigonal bipyramidal coordination geometry, matching the crystal structure of the Cu complex, while the μ = 5.52 μ value for the Mn complex suggests it is high spin octahedral. Cyclic voltammetry in acetonitrile revealed reversible redox processes in all three complexes, suggesting catalytic reactivity involving electron transfer processes are possible for these complexes. Screening for oxidation catalysis using hydrogen peroxide as the terminal oxidant identified the Fe complex as the oxidation catalysts most worthy of continued development.