Preparation, Properties, and Structures of the Radical Anions and Dianions of Azapentacenes

A series
of diazapentacenes (5,14-diethynyl­dibenzo­[b,i]­phenazine, 6,13-diethynylnaphtho­[2,3-b]­phenazine) and tetraazapentacenes (7,12-diethynylbenzo­[g]­quinoxalino­[2,3-b]­quinoxaline, 6,13-diethynylquinoxalino­[2,3-b]­phenazine) were reduced to their radical anions and dianions,
employing either potassium anthracenide or lithium naphthalenide in
THF. The anionic species formed were investigated by UV–vis–NIR,
fluorescence and EPR spectroscopy, spectroelectrochemistry, and quantum
chemical calculations. Single crystal X-ray structures of three of
their radical anions and of three of their dianions were obtained.
In contrast to the acenes, the anions of the azapentacenes are persistent
and, in some cases, even moderately stable toward air, and were characterized.