Reversible redox reaction between antiaromatic and aromatic states of 32π-expanded isophlorins.
32π-Antiaromatic expanded isophlorins with a varying number of thiophene and furan rings adopt either planar, ring-inverted, or twisted conformations depending on the number of furan rings in the macrocycle. However, they exhibit identical reactivity with respect to their oxidation to aromatic 30π-dicationic species under acidic conditions. These 32π-antiaromatic macrocycles can also be oxidized with [Et3O(+)SbCl6(-)] and NOBF4 to generate dications, thus confirming ring oxidation of macrocycles. Furthermore, they can be reduced back to their parent 32π-antiaromatic state by triethylamine, Zn, or FeCl2. Single-crystal X-ray diffraction analysis confirmed a figure-eight conformation for a hexafuran system, which opens to a planar structure upon oxidation.
Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune-411008, Maharashtra (India).
Tullimilli Y
TY
Gopalakrishna
Venkataramanarao G
VG
Anand
aromaticity; electron transfer; heterocycles; macrocycles; porphyrinoids