Oxidative Transformation of a Tetrathia S‑Confused Isophlorin into Porphyrin Cation

The synthesis and redox properties
of first generation S-confused
isophlorins are described. Despite structural resemblance to a confused
porphyrin, spectroscopic and computational studies reveal weak paratropic
ring current effects in these 20π macrocycles. They display
redox properties atypical of parent tetrathia isophlorins. Experimental
evidence supports the oxidation of an unstable 19π neutral radical,
as a transient intermediate, for the formation of a unique 18π
aromatic monocationic species. Spectroscopic and structural characterization
revealed the substituent dependent macrocycle oxidation unfamiliar
to the chemistry of antiaromatic isophlorinoids.