Electronic and Magnetic Study of Polycationic Mn12 Single-Molecule Magnets with a Ground Spin State S =11

The preparation, magnetic characterization, and X-ray structures of two polycationic Mn12 single-molecule magnets[Mn12O12(bet)16(EtOH)4](PF6)14 3 4CH3CN3 H2O (1) and [Mn12O12(bet)16(EtOH)3(H2O)](PF6)13(OH) 3 6CH3CN3 EtOH3H2O (2)(bet = betaine = (CH3)3Nþ-CH2-CO2 ) are reported. Interestingly, bond valence sum calculations extracted from X-ray diffraction data indicate the presence of two Mn 2+ ions in the Mn12 core for both 1 and 2.This finding is confirmed by X-ray absorption spectroscopy (XAS) measurements. A complete magnetic characterization,including subkelvin micro-SQUID magnetometry and inelastic neutron scattering (INS) measurements, permits to extract theparameters of the giant spin Hamiltonian of these polycations. Compared with the archetypal Mn12 acetate, an increase in thevalue of the ground spin state from S=10 to S=11 together with a decrease in the effective energy barrier, is observed for 1 and 2. Such a result is consistent with the reduction of two Mn 3+ to the less anisotropic Mn 2+ ion in the structures.