A new functionalised oligopyridine ligand containing ferrocene as a ball-bearing spacer for metallosupramolecular chemistry

A new supramolecular building-block in which a ferrocene moiety has been used as a spacer linking two terpyridyl units has been prepared. The new multidentate ligand 1,1′-bis(2,2′:6′,2″-terpyridin-4′-yl)ferrocene (tft) incorporates two tridentate metal-binding domains. The ligand has been synthesised from ferrocene-1,1′-dicarbaldehyde and 2-acetylpyridine in a two- stage procedure. The reaction of ferrocene-1,1′-dicarbaldehyde with 2-acetylpyridine yields the bis-chalcone 1,1′-[3-oxo-3-(2- pyridyl)prop-2-en-yl]ferrocene which has been structurally characterised: monoclinic, space group P2₁/_c (No. 14) with a=13.126(3), b=10.470(2), c=15.642(3) Å, β=111.62(3)° and Z=4, R₁ 0.052 (F>4σ(F), for 1611 reflections) and R₂ 0.125 (all data). The cyclopentadienyl rings of the ferrocene are eclipsed and the two 2,2′:6′,2″-terpyridinyl moieties are in a stacked coplanar conformation. The reaction of this chalcone with N-[1-oxo-2-(2-pyridyl)ethyl]pyridinium iodide and ammonium acetate yielded the new ligand as an orange solid which was structurally characterised: monoclinic, space group P2₁/c (No. 14), a=13.268(3), b=18.147(4), c=12.458(2) Å, β=90.73(3)° and Z=4, R₁ 0.077 (F>4σ,(F), for 2041 reflections) and R₂ 0.217 (all data). Once again, the cyclopentadienyl rings of the ferrocene are eclipsed and the two 2,2′:6′,2″-terpyridinyl moieties are in a stacked coplanar conformation.