Synthesis and Characterization of Ternary Manganese–Nickel–Iron Prussian Blue Analogues: Bridging Coordination Chemistry and Solid-State Physics

Ternary Prussian blue analogues (t-PBAs) containing nickel, manganese, and iron were synthesized via a facile aqueous coprecipitation method to investigate how Mn/Ni ratios influence structural and electrochemical properties. X-ray diffraction, combined with thermal and spectroscopic analyses, showed a systematic dependence of structural parameters on the manganese content, which also impacts the number of coordinated water molecules, suggesting a less defective Fe(CN)6 framework, and weakens the Fe–CN bond. The kinetics and thermodynamics of Ni2+ and Mn2+ ions in water during nucleation were correlated with ligand-exchange behavior, clarifying their impact on crystalline coherence. The presence of nickel was found to be the key to stabilizing the materials against changes induced by light irradiation and bias solicitation. Indeed, electrochemical measurements demonstrated that Ni-rich analogues exhibit superior stability and capacitance retention, whereas Mn-rich counterparts show an increased capacitive behavior but poorer cycling durability. These findings bridge coordination chemistry and solid-state physics in t-PBAs, providing design guidelines for mixed-metal frameworks with tunable properties.