Multimetallic, double-stranded helical complexes derived from hexa(n-propylthio)novipyridine: synthesis, structure and redox properties

4′,4′′,4′′′,4′′′′′,4′′′′′′,4′′′′′′′-Hexa(n-propylthio)-2,2′;6′,2′′:6′′,2′′′:6′′′,2′′′′:6′′′′,2′′′′′:6′′′′′,2′′′′′′:6′′′′′′,2′′′′′′′:6′′′′′′′,2′′′′′′′′-novipyridine (L), a new nonadentate ligand, reacts with cuprous tetrakis(acetonitrile) hexafluoro-phosphate in oxygen-free methanol at room temperature to yield the black, crystalline cuprous complex [L2CuI5][PF6]5. In the presence of air the corresponding mixed-valence complex [L2CuIICuI3][PF6]5 is obtained. Reaction with CuII and CoII ions resulted in the formation of the corresponding trimetallic complexes [L2MII3][PF6]6. Molecular compositions were established from partial elemental analysis, FAB mass spectral data, and from electrochemical and electronic spectral data. [L2CuI5]5+ contains the most cuprous ions assembled in a oligopyridine complex to date and these complexes, analogous to others in this series, were assigned double-stranded helical structures. An intramolecular diastereotopic effect in the 1H NMR spectrum of the diamagnetic pentacuprous complex showed its chiral nature and its stability in solution. Electrochemical studies of these complexes showed appreciable metal–metal interactions, and redox-induced transformations among the copper helicates were established spectroelectrochemically.