Tuning the redox profile of the 6,6′-biazulenic platform through functionalization along its molecular axis

The E 1/2 potential associated with reduction of the linearly-functionalized 6,6′-biazulenic scaffold is accurately correlated to the combined σ p Hammett parameters of the substituents over >600 mV range. X-ray crystallographic analysis of the 2,2′-dichloro-substituted derivative revealed unexpectedly short C-Cl bond distances, along with other metric changes, suggesting a non-trivial cycloheptafulvalene-like structural contribution. The one-step, two-electron reversible reduction of the 6,6′-biazulenic scaffold functionalized along its molecular axis is quantitatively tunable within a wide range of potentials.