Discuss effects of complexation on electrode potential?
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6.14 Change in Reduction Potential
The reduction potential of a species is its tendency to gain electrons and get reduced. It is measured in millivolts or volts. Larger positive values of reduction potential are indicative of a greater tendency to get reduced. We have seen earlier that the complex formation is accompanied by a decrease in the ionic activity of the metal. Therefore, the reduction potential of the metal ion decreases upon complexation.
The standard reduction potential for a free Co+3 ion is 1.853 V, while in complexed state [Co(NH3)6]+3, it decreases to 0.1 V. Similarly, a free Fe+3 ion has a standard reduction potential of 0.771 V, but [Fe(CN)6]−3 has the value of 0.36 V.
In general, a decrease in reduction potential upon complex formation has been observed. This means that the higher oxidation states of the metal ion become more stable after complexation. This change in reduction potential, although not popular in synthetic coordination chemistry, can be made as a basis for the detection of complex formation.