Structural Versatility and Supramolecular Isomerism in Redox-Active Tetra- and Hexaruthenium Macrocycles

We report on six macrocyclic tetra- and hexaruthenium complexes formed by the self-assembly of 2,5-divinylthiophene- or 2,5-divinylfuran-bridged diruthenium and 2,5-thiophene-, -furan- or -pyrroledicarboxylate linkers. All complexes were scrutinized by NMR spectroscopy and UHR ESI-MS, cyclic and square wave voltammetry and, in five cases, by X-ray diffraction analyses. Although the utilized building blocks differ only slightly with respect to their intrinsic bite angles, the resulting macrocycles exhibit remarkable structural versatility. Electrolysis inside an optically transparent electrochemical (OTTLE) cell provided their associated di-/tri- and tetra-/hexacations, which were studied by IR, UV/Vis/NIR and EPR spectroscopy. The divinylthiophene-furandicarboxylate complex 2-TF provides a rare example of supramolecular isomerism in metallamacrocyclic complexes. Thus, hexanuclear 2-TF6 is initially formed as a kinetic isomer, which subsequently transforms slowly and cleanly into tetranuclear 2-TF4.