Crystal lattice effect on the quenching of the intracluster magnetic interaction in [V_(12)B_(18)O_(60)H_6]~(10?) polyoxometalate

摘要

In the present work, the synthesis and structural characterization of four new polyoxovanadoborate (BVO) frameworks based on the [V_(12)B_(18)O_(60)H_6]~(10?) polyanion are reported: (NH_4)_8(1,3-diapH_2)- [V_(12)B_(18)O_(60)H_6]·5H_2O (1), K_8(NH_4)_2[V_(12)B_(18)O_(60)H_6]·18H_2O (2), K_(10)[V_(12)B_(18)O_(60)H_6]·10H_2O (3) and K_8Cs_2[V_(12)B_(18)O_(60)H_6]·10H_2O (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.