Conclusion Measurement of the redox levels for two series of pyrylium and thiapyrylium salts has provided a quantitative comparison of the effect of oxygen vs. sulfur on the thermodynamic stabilities to electron transfer of nitrogen-cationic, carbon-radical, and carbon-anionic centers in a single system. The ionic and radical species localized on the pyrylium-thiapyrylium ring system prefer to be adjacent to sulfur. The order of greatest ...
