Molecular magnetism in closo -azadodecaborane supericosahedrons

Abstract

The connection of 12 s = ½ closo-azadodecaborane radical units (NB11H11•), where a hydrogen atom is removed from the nitrogen atom, produces a supericosahedron [(NB11H6•)12](S), S being the total spin of the system. This work describes the study of the low-lying energy spin-projected states of this supericosahedron with two different geometrical arrangements, each nitrogen atom pointing (1) inwards or (2) outwards with respect to radial axes. These spin-projected states are mapped into a Heisenberg spin Hamiltonian, thus allowing the determination of coupling constants between magnetic sites. The eigenvalues of this model Hamiltonian then predict the ground spin state and the corresponding combinations of spin orientations of the magnetic centres. We show that the energy minimum in the [(Nin/outB11H6•)12](S) systems corresponds to a high-spin S = 6 state.