Late-Stage Modification of Electronic Properties of Antiaromatic and Diradicaloid Indeno[1,2‑b]fluorene Analogues via Sulfur Oxidation

The ability to alter optoelectronic and magnetic properties of molecules at a late stage in their preparation is in general a nontrivial feat. Here, we report the late-stage oxidation of benzothiophene-fused indacenes and dicyclopentanaphthalenes to their corresponding sulfone derivatives. We find that while such modifications increase the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap to a small degree, other properties such as HOMO and LUMO energy levels, molecule paratropicity, and singlet-triplet energy gaps are influenced to a greater degree. The most surprising finding is a change of the bond alternation pattern within the s-indacene core of the sulfones. Computations corroborate the experimental findings and offer plausible explanations for these changes in molecular properties.