[V16O38(CN)]9–: a soluble mixed-valence redox-active building block with strong antiferromagnetic coupling.

A new discrete [V(16)O(38)(CN)](9-) cluster, which displays the hitherto unknown 8- charge on the cluster shell and is the first to encapsulate the cyanide anion, has been synthesized and characterized by IR and UV/vis/near-IR spectroscopy, electrochemistry, and magnetic susceptibility measurements. Bond valence sum calculations conducted on the basis of the crystal structure analysis of K(9)[V(16)O(38)(CN)]·13H(2)O confirm that this new member of the polyoxovanadate series is a mixed-valence complex. The intervalence charge transfer bands arising from intrametal interactions reveal that a localized (class II) assignment is appropriate for the cluster; however, a small degree of electronic delocalization is present. Interesting possibilities exist for the incorporation of this unit into higher dimensionality framework structures, where the redox, optical, and magnetic properties can be exploited and tuned.