The dimeric [V₂O₂F₈]^4- anion: Structural characterization of a magnetic basic-building-unit

New materials built from the [V₂O₂F₈] ^4- anionic basic-building-unit (BBU) exhibit interesting magnetic properties owing to the proximity of the two d¹ V(IV) cations and the orbital interactions of fluoride and oxide ligands. In our search to target such materials, the vanadium oxide-fluoride compound [dpaH₂] ₂[V₂O₂F₈] in which a dimeric anion [V₂O₂F₈]^4- is isolated in a hydrogen bond network was hydrothermally synthesized (dpa=2,2′-dipyridylamine). This hydrogen bond network is able to stabilize the highly ionic species [V ₂O₂F₈]^4- as demonstrated with bond valence calculations. The coordination of the O^2-/F^- ordered ligands was investigated and antiferromagnetic coupling of the isolated BBU was measured.