Complexes of Cobalt in Different Metal Oxidation States Biology Essay
During the oxidative dissolution of metal sulfides, several sulfur compounds occur with an intermediate oxidation state between sulfide -2 and sulfate, 6. Iron III ions and molecular oxygen, as well as manganese oxides and nitrate, have been described as oxidizing agents for metal sulfides and for intermediate sulfur compounds Schippers, 2. Cobalt III Ions in Biological Systems. Only a small number of cobalt III complexes are known to play a biochemical role. Vitamin is a cobaloxime, a cobalt complex containing a glyoxime ligand, and is one of the rare examples of a naturally occurring organometallic complex, that is, possessing a metal-carbon bond. Due to its structure, Schiff base ligands are able to coordinate many different metals and stabilize them in different oxidation states, allowing the use of Schiff base metal complexes for a wide variety of useful applications. X-ray absorption near-edge structure XANES spectroscopy was used to monitor the oxidation state of cobalt after treatment of Co-III complexes with reducing agents such as ascorbate and cysteine. Cobalt III complexes have a large absorption peak at lower energies, at ca., and a neighboring peak eV, with post-edge minima, eV. 47, highlight. The bond length, bond angle and coordination site vary depending on the metal and its oxidation state. In addition, metal-based complexes can be structurally modified into a variety of different molecular species yielding a broad spectrum of coordination numbers and geometries as well as kinetic properties that may not yet be state-of-the-art. homogeneous water oxidation catalysis is efficiently performed with expensive, toxic and earth-scarce transition metals; metal-based catalysts are much less so. A Natural Bond Orbital theory method for determining the oxidation states of transition metals in a variety of complexes has been presented. There are a number of important points to note regarding this method. 1 This method is very general, in the sense that any electronic structure program containing NBO analyzes can be observed. The electrochemical behavior of the cobalt II complexes, the Co III Co II pair, can be observed. Their positive potential indicates that metal in a lower oxidation state is strongly bound to these ligands. The difference between the potential of the anodic peak and the cathodic peak remains constant in all complexes.