Spectroelectrochemical Studies of the Reductive Intermediates of Anthraquinone-2,6-Disulfonate in Aqueous Media

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Weiss, Anna
thesis / dissertation description
Reactive intermediates in the reduction of anthraquinone-2,6-disulfonate (AQDS) by dithionite combine to form a transient dimer which has shown to give rise to a series of charge transfer bands in the visible range (600-750 nm). Additional wavelengths associated with these intermediate species have been observed at wavelengths 402, 444 and 510 nm. These transient intermediates are generated as dithionite decomposition products re-oxidize AQDS. Evidence of the dimer was also found in experiments in which reduction of AQDS was achieved electrochemically by the use of a potentiostat. This implies three things: 1. dithionite is not required for dimerization of reactive intermediates; 2. the dimerization reaction is reversible; 3. the dimer formation reaction involves an intermediate common to both oxidation and reduction.In addition our studies have also led to evidence of such a dimer in unbuffered aqueous solution at neutral pH. Dimer formation is enhanced in the presence of clay. Clay appears to stabilize the dimer species via both kinetic and thermodynamic effects.