Precise Synthesis of Alternate Fe(II)/Os(II)-Based Bimetallic Metallo-Supramolecular Polymer

A novel terpyridine-based bimetallic metallo-supramolecular polymer (polyFeOs) containing alternately complexed Fe(II) and Os(II) ions is synthesized. For precise synthesis of the polymer, a new three-step synthetic pathway is developed to obtain a high yield (%) of product in each step. The first step is the synthesis of dibromo terpyridine-Os(II) complex in 87% yield, the second step is the synthesis of bisterpyridine ligand containing Os(II) (OsL1) in 74% yield, and the last step is the synthesis of polyFeOs in 90% yield. The polyFeOs exhibits high thermal stability with two degradation temperatures at around 390 and 690 °C, which indicate thermal evaporation of the counter anions (Cl⁻ and BF₄ ⁻) and degradation of the coordination bonds, respectively. The combination of two different metal ions in polyFeOs results in an enlarged optical window (λ = 315–675 nm) and two highly stable reversible redox states, which can be of huge interest for potential optical, electro-optical, and electrochemical applications.