Dioxadiazuliporphyrin: A Near-IR Redox Switchable Chromophore

The synthesis of dioxadiazuliporphyrinogen 7 and its oxidized forms:  dioxadiazuliporphyrin 8 and dication
82+, is reported. These compounds were characterized in solution using UV−vis and 1H and 13C NMR
spectroscopic means and in the solid state via single-crystal X-ray diffraction analysis. Dioxadiazuliporphyrin is a nonaromatic porphyrinoid, readily and reversibly oxidizable to its cation radical and to the
aromatic carbaporphyrinoid dication, which can be viewed as a 21,23-dicarba-22,24-dioxaporphyrin with
two fused tropylium rings. Further insight into the geometric and magnetic manifestations of aromaticity
and antiaromaticity in the case of the redox couple 8, 82+ is obtained using density functional calculations
and nucleus-independent chemical shifts.