Indeed, according to EDDB these species are devoid of electron delocalization in the valence subshell because merely 0.2041 and 0.2075e are delocalized in P4 and Si4 ). Although the HOMO of 16 is triply degenerate and described purely by radially oriented p AOs, HOMO-1 and HOMO-2 are nondegenerate, and HOMO-3 is a mix of radially and in-plane oriented p. Thus, 16 should not be labelled as a 3D-aromatic that fulfills the 6n + 2 rule for tetrahedral or octahedral molecules, and the same applies to 14 and 15. Clearly, as the local bond orbitals with either in-plane or radial orientations mix for the tetrahedra, the polyyne linkers are not suitable for construction of tetrahedral -conjugated 3D-aromatics. In contrast, in the cubic 18, combinations of radially (24) and C8(C6H6)8 ( ) the polyene linkers lead to structures which are distorted (C2 symmetric) with weaker delocalization (35%) than found for the corresponding polyyne-linked species (Figure ). Furthermore, they exhibit significant bond length alternations as seen for