Chromium complexes biological effects

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

Change in the oxidation state of an element can have a profound effect on bioavailability and toxicity. Fe(II) is biologically the main usable form of iron, Fe(III) in excess can cause stomach lesions.When chromium appears as a pollutant in a sample of river water or in a Cr complex dye, its valency is of relevance in ascertaining the relative toxicity of the sample. Trivalent chromium is an essential element in mammalian systems, hexavalent chromium is considered to be a moderate to severe industrial hazard. 

Chapter 13 by Levina, Codd, and Lay, deals with possible medical applications of chromium compounds. Carcinogenicity and antidiabetic effects of chromium compounds, originally thought to be quite distinct biologically, are found to depend on varying amounts of Cr (VI) and reactive intermediates, such as Cr (V) species, formed in vivo either by reduction of Cr (VI) or by oxidation of Cr (III) complexes. The cartoon in Figure 1 should prove very helpful to those readers unfamiliar with chromium chemistry and its applications. 

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