Alignment of Acentric Units in Infinite Chains: A “Lock and Key” Model

Polar chains built from acentric building units are of importance to investigate the mechanisms driving the polar alignment in the solid state. Our attempts to engineer polar chains in mixed metal oxide fluorides M′(2,2′-bpy)­(H2O)2MOxF6–x compounds [M′/M = Cu/Ti, Cu/V, Cu/Nb, Cu/Mo, Zn/Mo, and Zn/W] were successful using a combination of acentric anions [MOxF6–x]2– and acentric cations [M′(2,2′-bpy)­(H2O)2]2+. A new general insight is also revealed: the alignment of polar units can be described with a “lock and key” model. The role of both the key (the acentric unit) and the lock (its environment) on the polarity in infinite chains is discussed.