Vanadium and molybdenum complexes with amino acid functionalized ligands
Vanadium was first discovered in 1801 by Andrés Manuel del Rio, a Spanish professor of mineralogy working in Mexico City. He originally named the element panchromium after the various color of its salts, but later renamed it erythronium because of the red color generated upon heating. Unfortunately, del Rio lost confidence in his discovery, thinking that he had found the element chromium, which had recently been discovered by the Frenchman Fourcroy. Vanadium was rediscovered in 1831 by the Swede Nils Gabriel Sefström. Its present name is derived from the Vanadis, the goddess of love and beauty of Norse mythology. Metallic vanadium was not isolated until 1867 when Sir Henry Enfield Roscoe, Professor of Chemistry at Owens College (later the University of Manchester), reduced vanadium chloride (VCl5) with gaseous hydrogen to give vanadium metal and HCl. Natural vanadium is a mixture of two isotopes, 51V (99.76%) and 50V (0.24%), the latter being slightly radioactive with a half-life of >3.9 x 1017 years. Important sources of the metal are the minerals carnotite [K2(UO2)2(VO4)2] and vanadinite [Pb(VO4)3Cl]. It is also present in some crude oils in the form of organic complexes. Vanadium occurs with an abundance of 0.014% in the earths crust and is widespread. The element is the second most abundant transition metal in the oceans (50 nM). Some aquatic organisms are known to accumulate vanadium. However, the actual function of vanadium and the nature of the vanadium compounds present in these organisms remains unclear. In 1983, a naturally occurring vanadium-containing enzyme, vanadium bromoperoxidase Figure 1.1: A tunicate (Clavelina Puertosecensis) discovered near Discovery Bay, Jamaica. (V-BrPO), was discovered in the marine brown alga Ascophyllum nodosum. Since then, several vanadium haloperoxidases have been isolated and studied, many of these enzymes have been detected in brown and red seaweeds.