Metallosupramolecules bearing pendant redox-active domains: Synthesis and co-ordination behaviour of the metallocene-functionalized helicand 4′,4″″-di(ferrocenyl)-2,2′:6′,2″:6″, 2‴:6‴,2″″:6″″,2‴″- sexipyridine

The novel ferrocene-functionalized helicand 4′,4″″-di(ferrocenyl)-2,2′:6′,2″:6″, 2‴:6‴,2″″:6″″,2‴″- sexipyridine (dfspy) has been obtained from the reaction of 6,6′-di(1-pyridinioacetyl)-2,2′-bipyridine diiodide and 2-[3-(ferrocenyl)-1-oxoprop-2-enyl]pyridine. However, a related route involving the condensation of 6,6′-di[3-(ferrocenyl)-1-oxoprop-2-enyl]-2,2′-bipyridine I with N-[2-oxo-2-(2-pyridyl)ethyl]pyridinium iodide does not give the desired sexipyridine derivative. In an attempt to understand these reactivity patterns the crystal structure of I has been determined by single-crystal X-ray methods: monoclinic, space group P2₁/n, a = 5.8780(10), b = 12.622(3), c = 24.860(5) Å, β = 93.33(3)°, Z = 4. A nickel(0) template procedure for the synthesis of dfspy from 6-bromo-4′-ferrocenyl-2,2′:6′,2″-terpyridine (bfterpy) has also been investigated. The co-ordination behaviour of the new redox-active compounds bfterpy and dfspy has been studied. The interaction of bfterpy with metal salts gives the mononuclear complexes [M(bfterpy)₂][PF₆]₂ (M = Fe, Co, Ni or Zn). In contrast, with dfspy the double-helical complexes [M₂(dfspy)₂][PF₆]₄ (M = Fe, Co, Ni or Zn) are formed.