Changing the electrochemical behavior of catechols by means of their conversion into the corresponding rughenium(II)-dioxolene complexes

摘要

The rather complicated electrochemicalbehavior,inaqueous solution,exhibited by catechol(1,2-dihydroxybenzene) and its derivatives containing carboxylate and sulponate groups,can be conveniently controlled by means of their conversion into the corresponding blue ruthenium(III)-edta complexes (edta-ethylenedinitrilotetraacetate ligand).In the free form,the catechol species undergo a primary electrocheical oxidation process in the range of 0.3-0.6V versus SHE,yielding quinone products susceptible to a numbe ro pH dependent,secondary chemicalreactionsWhen Coordinated to the ruthenium(III-edta unit,their electrochemical andspectroelectrochemical behavior is dramatically changed,approaching that of metal complexes with non-innocent dioxoleneligands.In this case,the reduction of the ruthenium (III) metalion proceeds reversibly above pH9,in the -(0.5-0.6)V range and theoxidation process centered on the catecholate ligands becomes reversible,leading exclusively to the formation of the semquinone species,withno evidence of complications from the secondary reactions.