Construction of Bis(2,6-bis(1-methylbenzimidazol-2-yl)pyridine)iron(II) Coordination Polymer for Incorporation of Magnetic Function

Low-dimensional coordination polymers are attractive materials because the infinite combination of metal ions and ligands allows us to produce various chemical structures and functions. Spin crossover (SCO) is one of the curious magnetic functions because the electronic state of metal complex can be controlled by external stimuli. It is expected that the introduction of SCO-active metal complex to a coordination polymer will contribute to produce a multifunctional material. In this research, a coordination polymer composed of ferrous ion and a ligand with 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (mbzimpy) ligating groups $$([\mathbf{FeL}_\mathrm{mbi}]_n)$$ was synthesized to incorporate SCO activity. The polymer was synthesized using a liquid–liquid interfacial reaction and a one-phase reaction, and was obtained as a film and a powder, respectively. Electrochemical and spectroscopic measurements revealed the formation of $$[\mathrm{Fe}(\mathrm{mbzimpy})_2]$$ complex. The magnetic susceptibility measurement displayed the partial SCO of $$[\mathbf{FeL}_\mathrm{mbi}]_n$$ polymer from 350 K to 250 K.