Key points are not available for this paper at this time.
Through “electronic separation” of the seven-membered ring the formally cross-conjugated, azulene-containing macrocycle (limiting structure A) becomes a porphyrinlike species with a weak, diamagnetic ring current (limiting structure B). This aromatic character is further accentuated upon twofold protonation.
Lash et al. (Fri,) studied this question.