Oxidizing-reducing entities, effect

To compete effectively with the photophysical processes, the chemical reactions from the highly energetic CT states should be very fast, otherwise the MC states become populated. On the other hand, redox processes may sometimes occur from other than CT excited states. The phenomenon is a consequence of redox potential changes after excitation, which make the entity in any excited state a much stronger oxidant and a much stronger reducer than the ground state complex, eg the standard oxidation potential of the [Fe(bpy)3]2+ complex is 1.05 V in the ground state and... 

Table I presents data from McFarlane al, (8) showing that the multi-step oxidation of L-tyroslne to p-hydroxymandelonltrlle requires only 02 and a source of reducing power, most effectively supplied by an NADFH generating system. The table also shows that some of the L-tyroslne Is converted to p-hydroxyphenylacetaldoxime (aldoxime) as well as a trace of p-hydroxyphenylacetonltrlle (nitrile). The production of the aldoxime and nitrile In this experiment was the first Indication that the microsomal preparation from sorghum might constitute an organized enzyme entity Involved In the synthesis of dhurrln. If this were true, it should be possible to demonstrate each individual step of the reaction sequence between tyrosine and p-hydroxymandelontrlle.

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