Abstract

In the present work, the synthesis and structural characterization of four new polyoxovanadoborate (BVO) frameworks based on the [V12B18O60H6](10-) polyanion are reported: (NH4)(8)(1,3-diapH(2))-[V12B18O60H6]center dot 5H(2)O (1), K-8(NH4)(2)[V12B18O60H6]center dot 18H(2)O (2), K-10[V12B18O60H6]center dot 10H(2)O (3) and K8Cs2[V12B18O60H6]center dot 10H(2)O (4). A global antiferromagnetic behaviour is observed for these 10V(IV)/2V(V) mixed valence clusters. The magnetic data of 1, 2 and 3, which present different countercation environments, show that 1 is more coupled than 2 and 3. DFT calculations show that the positive charges strongly influence the polarization mechanism of the spin density of the vanadyl groups and the extent of the magnetic orbitals, therefore corroborating the experimental observation of the quenching effect of the magnetic coupling between vanadium centres of 2 and 3.