Radicals Containing a Dithiin Ring

There have been several theoretical descriptions of 171, 172, and related systems. Both McLachlan and INDO MO calculations show modest improvement on inclusion of ( -electrons in the basis set. 

Dithiino[3,4-6]dithiin (174) has been synthesized and subjected to anodic oxidation. Although the formation of a radical is implied, it occurs at much higher voltage than the oxidation of isomeric tetrathiafulvalene to 153 electrically conducting charge-transfer salts are not formed by 174. 

Gerson and co-workers ° have formed both cation- and anion-radicals from the heterocycle dithieno[3,4-6 3, 4 -e][l,4]dithiin-l,3,5,7-tetraone 

The only other simple 1,4-dithiin anion-radical to have been documented is 176. This shows the ESR spectrum expected from four equivalent nitrogen nuclei. (The indicated hyperfine splitting is in gauss.) The authors draw attention to the low -value of 176, indicative of little spin population on S they argue that the conjugation in the radical may well short-circuit the heteroatoms and arise from direct overlap of the ir-systems on carbon, being possible on account of the nonplanarity (folding) of 176. 

Thianthrene cation-radical 178 is one of the most studied of heteroaromatic radicals. Its individual chemistry has proved very rich additionally, it is a persistent, readily recognized radical which has often been used as a well-behaved radical in systems where the prime interest has been the physical chemistry rather than the substrate itself. This chapter cannot deal fully with the chemistry of 178 however, aspects have been reviewed on several and recent occasions.  

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