Three intersecting {V12} rings: {V30Sb8}, an ultra-large polyoxovanadate cluster shell

Abstract

[V^IV₃₀Sb^III₈O₇₈]¹²⁻, currently the largest known antimonato-polyoxovanadate (Sb-POV), features three perpendicular, intersecting 12-membered rings of edge-sharing O₄VO square pyramids. While in two rings the apices of all O₄VO pyramids point outwards, four apices of the third ring are directed into the cavity of the cluster shell, a concave structural motif not previously observed in polyoxovanadate chemistry. Sb^III centers cap the eight niches defined by the octands of the {V₃₀O₇₈} cluster shell, resulting in discrete trigonal pyramidal SbO₃ units, a second unprecedented feature. Within the resulting spin topology with numerous local geometrically frustrated motifs, the 30 spin-1/2 sites couple antiferromagnetically via a complex set of exchange pathways.