The structure of indoloindolizine I6 was unambiguously confirmed with single-crystal X-ray diffraction analysis (Figure ). In the crystal, I6 forms dimeric structures in an antiparallel configuration, which are organized within the crystalline matrix into two distinct domains oriented at an approximate angle of 65 degrees relative to each other. The polycyclic cores of these dimers are situated a mere 3.36 Å apart. Such compact intermolecular distance is presumably a consequence of antiparallel dipole-dipole interactions, driven by the intrinsic dipole moments inherent to the indoloindolizine's asymmetric polycyclic framework. A detailed examination of bond lengths within the polycyclic core of I6 reveals a pronounced delocalization, evidenced by small bond-length alternation (BLA), within ring A (Figure ). Conversely, rings B, C, D, and E exhibit more localized electronic environments, as indicated by increased BLA values (Figure ). These differences suggest the presence of distinct aromatic substructures within these segments (vide infra). It is worth noting that the observed BLA in I6 is consistent with the computed ISE values in M6, where ring A has the highest ISE value among all other rings (Figure ).