Cu(C₁₀H₉N₃)₂MOF₅·2H₂O (M = Nb, Ta):  Aligned [MOF₅]²⁻ Oxide Fluoride Anions

Two new compounds are reported that contain a 1:1 complex of a cis-bis(2,2‘-dipyridylamine)Cu2+ cation and an oxide fluoride [MOF5]2- (M = Nb, Ta) anion in which the polar distortions of the anions are aligned within one-dimensional chains. The bonding and charge on the oxide and fluoride ions and the distortions of the [NbOF5]2- and [TaOF5]2- anions resemble the ferroelectric material lithium niobate.