Outer inorganic redox processes

Since most inorganic redox processes take place between two metal complexes, they are classified according to the behaviour of the inner (first) co-ordination spheres (shells) in the transition state (Basolo and Pearson, 1967). In the transition state of an outer-sphere mechanism the inner co-ordination spheres of both metal ions are intact, i.e., no ligand to metal bond is broken or formed, whereas in the transition state of an inner-sphere mechanism a bridging ligand,... 

The thioester hypothesis can be summed up as follows the formation of thiols was possible, for example, in volcanic environments (either above ground or submarine). Carboxylic acids and their derivatives were either formed in abiotic syntheses or arrived on Earth from outer space. The carboxylic acids reacted under favourable conditions with thiols (i.e., Fe redox processes due to the sun s influence, at optimal temperatures and pH values) to give energy-rich thioesters, from which polymers were formed these in turn (in part) formed membranes. Some of the thioesters then reacted with inorganic phosphate (Pi) to give diphosphate (PPi). Transphosphorylations led to various phosphate esters. AMP and other nucleoside monophosphates reacted with diphosphate to give the nucleoside triphosphates, and thus the RNA world (de Duve, 1998). In contrast to Gilbert s RNA world, the de Duve model represents an RNA world which was either supported by the thioester world, or even only made possible by it. 

It should be emphasized that the majority of electrochemically induced redox processes in inorganic chemistry proceed (or are assumed to proceed) through outer-sphere mechanisms. 

The aim in solution studies on metalloprotein is to be able to say more about intermolecular electron transfer processes, first of all by studying outer-sphere reactions with simple inorganic complexes as redox partners. With the information (and experience) gained it is then possible to turn to protein-protein reactions, where each reactant has its own complexities... 

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