Metallo-polymerization/-cyclization of a C16-bridged di-terpyridine ligand and iron(II) ions

The coordinative polymerization/cyclization of a flexible monodisperse di-terpyridine ligand with iron(II) chloride is reported. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) investigations showed the preferred formation of a [2 + 2] macrocycle, but also larger aggregates (cycles or linear oligomers) with up to 10 monomer units were found. Because of its C-16-spacer, the solubility is sufficient for performing viscosity experiments in CHCl3/MeOH solution. A viscosity titration revealed a maximum in viscosity at the 1-to-1 ratio of iron(n) ions to di-terpyridine-ligands, which indicates the formation of extended oligomers, polymers, catenanes and/or cycles at that ratio.