Synthesis and Theoretical Studies of a Double Helical Complex with the Ligand 4′,4′′′‐Bis(ferrocenyl)‐2,2′:6′,2′′:6′′,2′′′:6′′′,2′′′′‐quinquepyridine

Abstract

Abstract 4′,4′′′‐Bis(ferrocenyl)‐2,2′:6′,2′′:6′′,2′′′:6′′′,2′′′′‐quinquepyridine (Fc 2 qpy) reacts with AgOTf (OTf = trifluoromethylsulfonate) to give a complex of stoichiometry [Ag(Fc2qpy)]OTf. The crystal structure reveals a dinuclear arrangement among the cations with an Ag ··· Ag close contact of 3.089(2) Å. The ligands are wrapped around the silver atoms in a double helical array. Further hydrogen bonding between triflate units and the protons of the ferrocene or pyridine moieties results in a supramolecular structure. Theoretical studies confirm the existence of a weak Ag−Ag bond, and show that the dinuclear form can be more stable than the mononuclear one, when there is a favorable balance between the reorganization energy of the two quinquepyridine chains and the energy released by the formation of stronger Ag−N bonds and the new Ag−Ag interaction in the helix. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)