Ruthenium voltammetric data

Cyclic voltammetry is an excellent tool to explore electrochemical reactions and to extract thermodynamic as well as kinetic information. Cyclic voltammetric data of complexes in solution show waves corresponding to successive oxidation and reduction processes. In the localized orbital approximation of ruthenium(II) polypyridyl complexes, these processes are viewed as MC and LC, respectively. Electrochemical and luminescence data are useful for calculating excited state redox potentials of sensitizers, an important piece of information from the point of view of determining whether charge injection into Ti02 is favorable. 

The oxidation of encapsulated ruthenium(II) ion to ruthenium(III) ion is a quasi-reversible process with Em from 1 430 to 1 140 mV. As on additional parameter, the cathodic and anodic current ratio (IpJIpa) obtained from voltammetric data was used to determine the relative stability of the resulting ruthenium (III) complexes. It was shown that the stability of these complexes increases with lengthening of the linear chain of alkoxy-groups and decreases with an increase in their volumes [77, 329]. 

Confirmation of the reaction mechanism is provided by kinetic data dependent upon the same pK for the N- l coordinated ruthenium(III) complex (see Figure 6) Owing to the instability of l-[(Ado)(NH3)3Ru(II)l and severe restrictions required of the oxidizing partner isomerization kinetic rates were derived from cyclic voltammetric data using the method of Nicholson and Shain " " after forming the N-1 coordinated Ru(II) complex at the electrode surface by electrolytic reduction of the N- 6 bound Ru(III) species. Since the specific rates estimated by this method were independent of concentration the rate law is taken to be first order in the complex. 

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