Electrochemical Li-ion intercalation in octacyanotungstate-bridged coordination polymer with evidence of three magnetic regimes

Discovery of novel compounds capable of electrochemical ion intercalation is a primary step toward development of advanced electrochemical devices such as batteries. Although cyano-bridged coordination polymers including Prussian blue analogues have been intensively investigated as ion intercalation materials, the solid-state electrochemistry of the octacyanotungstate-bridged coordination polymer has not been investigated. Here, we demonstrate that an octacyanotungstate-bridged coordination polymer Tb(H₂O)₅[W(CN)₈] operates as a Li⁺-ion intercalation electrode material. The detailed magnetic measurements reveal that the tunable amount of intercalated Li⁺ ion in the solid-state redox reaction between paramagnetic [W^V(CN)₈]^3- and diamagnetic [W^IV(CN)₈]^4- in the framework enables the electrochemical control of different magnetic regimes. While the initial ferromagnetic long-range ordering is irreversibly lost upon lithium insertion, electrochemical switching between paramagnetic and short-range ordering regimes can be achieved.