Configurational and Conformational Isomeric Antiaromatic [28]Tetraoxaporphyrinoids(4.2.4.2) and Aromatic [26]Tetraoxaporphyrin(4.2.4.2) Dications. A New Type of Molecular Dynamics in Macrocyclic SystemsThe [28]tetraoxaporphyrinoids(4.2.4.2)6are synthesized by cyclizingWittigreaction of (E, E)‐5, 5′‐(buta‐1, 3‐diene‐1, 4‐diyl)bis[furan‐2‐carbaldehyde] (8) with (E, E)‐{(buta‐1, 3‐diene‐diyl)bis[(furan‐5, 2‐diyl)methylene]}bis‐[triphenylphosphonium]dibromide (9) and 3, 3′‐{[(E)‐ethene‐1, 2‐diyl]bis(furan‐5, 2‐diyl)}bis[(E)‐prop‐2‐enal] (22) with (E)‐{(ethene‐1, 2‐diyl)bis[(furan‐5.2‐ diy)methylene]}bis[triphenylphosphonium]dibromide (23). An alternative path to get6is theMcMurrycondensation of8. Four different configurational isomers of6could be isolated and characterized by1H‐NMR spectroscopy. The (Z, EE, Z, EE)‐isomer6ais the first macrocyclic system where the inner and outer protons of the (E, E)‐dienediyl bridges exchange by rotation around the adjacent single bonds. In the (Z, EE, E, EE)‐isomer6b, the (E)‐ethenediyl bridge is rotationally active, while in the (E, ZE, E, EZ)‐isomer6cand in the (E, EZ, E, EZ)‐isomer6e, the rotation of both (E)‐ethenediyl bridges is observed. When in the dynamic systems the rotation of the active (E)‐double bonds at temperatures T<−90° is frozen, all configurational isomers of6appear to be antiaromatic and paratropic. The oxidation of the [28]tetraoxaporphyrinoids6cand6ewith DDQ yields the aromatic, diatropic [26]tetraoxaporphyrin(4.2.4.2) dications21e/21e′ both with (E, EZ, E, EZ)‐configuration but different fixed conformations. (Z, EE, Z, EE)‐Isomer6ais oxidized to give the (Z, EE, Z, EE)‐dication21a, while the oxidation of6byields a mixture of21aand21e/21e′. The standard formation enthalpies of the obtained and expected [28]tetraoxaporphyrinoids6and [26]tetraoxaporphyrin dications21hav