Publication Date

12-1975

Advisor(s) - Committee Chair

Robert Farina, Charles Henrickson, John Reasoner

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

The effects of ionic strength and various anions on the rate of electron transfer between tris(2,2'-dipyridine) cobalt(III) and bis(2,2',2"-tripyridine) cobalt(II) complexes have been examined in acetophenone. The redox rate was found to increase with increasing ionic strength in both the presence and absence of added salts. The reaction was first order with respect to each reactant and second order overall in all cases. The influence of the C104, BF4, and B(C6H5)4 anions on the reaction rate was studied with their order of effectiveness being: C104- > BF4 >> B(C6H5)4.

The reverse trend occurs in their ion pairing properties where the large size of the B(C6F5)4 stronger anion exerts a much stronger tendency to form ion pairs with the large reactant cations than either of the C104 and BF4 species. The proposed rate law in the presence of the C104 and BF4 anions was as follows:

Rate = Kx[Co(dipy)3/3+][Co(tripy)2X+

where the rate is independent of the anion concentration. An alternate rate law was proposed for the B(C6H5)T4 anion where a greater degree of ion pairing was obtained. In the absence of added salts, the redox rate Is believed to occur by two different reaction pathways.

Activation parameters were determined for each salt system as well as in the absence of added salts at µ = 0.0027 M and over a temperature range of 25-41°C. Factors affecting the activation parameters are discussed.

Disciplines

Chemistry | Physical Sciences and Mathematics

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