Adding vanadyl sulfate to an acidified molybdate solution, in presence of K+ cations, results in
formation of the compound abbreviated as [V30Mo72]. The vanadyl ions form a slightly
distorted icosadodecahedron. This fascinating, highly symmetric structure is a spherical arrangement of
pentagons and triangles. The S = 1/2 vanadyl ions are strongly exchange coupled. Quantum Monte Carlo simulations
show that the average interaction is around J = 245 K. Strong exchange interactions between vanadyl ions
despite long exchange pathways is a phenomenon that has been found in other vanadyl polyoxomolybdates. It is
much stronger than the exchange interaction in [Fe30Mo72]. The higher spin of the iron
ions (S = 5/2) compared to vanadium allowed the application of various classical calculation methods in that case.
In that sense [V30Mo72] can be compared as the quantum analogue of [Fe30Mo72] Figure: (top) Combined polyhedral and ball-and-stick representation of the structure of [V30Mo72], showing the triangles and pentagons of the icosidodecahedron, and additionally the basic {VO5} and {VO6} units as green polyhedra; (Mo atoms blue, O atoms red, K atoms purple, and SO42- groups yellow tetrahedra, disordered S atoms yellow). |