Tetrachalcogenafulvalenes, oxidation

The electrochemical oxidation potentials of various tetrachalcogenafulvalenes are compiled in Table 13. As the size of the heteroatom increases, the gap between Z71/2 for the first oxidation potential and iJ1/2 for the second oxidation potential narrows. This is presumably due to more localization of the radical cation on the heteroatom lone pairs. As the size of the heteroatoms increases, overlap with the adjoining rr-framework becomes less efficient. 

Table 13 Electrochemical Oxidation Potentials of Tetrachalcogenafulvalenes at a Platinum Electrode...

A tetrachalcogenafulvalene can be oxidized in two discrete steps, each step giving rise to a Huckel-type [4n -I- 2] aromatic delocalized r-system, thus for tetraselenafulvalene (TSF) (7), Scheme 2 results. 

Comprehensive reviews covering the electrochemical data for selenium- and tellurium-based tetrachalcogenafulvalenes have appeared, as mentioned in the introduction <87SR155,93SR245). Table 2 gives the half-wave oxidation potentials for selected representative examples of the selenium- and tellurium-based donors. 

Table 2 Half-wave oxidation potentials for selected tetrachalcogenafulvalenes.

These kinds of substitutions affect on the polarity, solubility, oxidation potentials and other physical and chemical properties of tetrachalcogenafulvalenes. Some examples are given in the following. 

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