What is "tetraanthraporphyrin"

Tetraanthraporphyrin, or tetraanthra[2,3]porphyrin (TAP), is a representative of extended porphyrins. Despite promising properties, tetraanthraporphyrins have until recently been little studied. As was theoretically predicted, extension of pi-electronic system results in the case of TAPs in the destabilization of the third LUMOs and the first HOMOs that makes it unstable against oxidation and reduction.