Magnetic interactions in novel molecule-based materials

Two molecule-based magnets have been studied to understand their magnetic interactions. The first of these magnets, utilizing diruthenium tetraacetate monocation, [RuII/III2(O2CCH3) 4]+, as a building block not only successfully produced a new family of molecule-based magnets, but more interestingly, exhibited anomalous phenomena. The first such phenomenon is the unusually low field-dependent magnetization that is a result of the removal of spin state degeneracy due to uniaxial spin anisotropy (zero-field splitting). The second phenomenon is observed as an unusual wasp-waisted shape hysteresis of [Ru2(O 2CMe)4]3[Cr(CN)6] at ambient pressure. This unusual behavior, however, reverses to a normal shape hysteresis when pressure is applied. From mathematical and computer modeling, the unusual hysteresis observed is attributed to the spin anisotropy and the antiferromagnetic interaction between the two interpenetrating ferrimagnetic lattices. Hence, [Ru2(O2CMe)4]3[Cr(CN)6] is a metamagnet, as it has an antiferromagnetic ground state, but undergoes a field-induced phase transition to a paramagnetic phase. The second molecule-based magnet, the newly discovered organic-based [FeII(TCNE •-)(NCMe)2][FeIIIC14] exhibited two behaviors of interest. First, the ferrimagnetic layered [FeII (TCNE•-)(NCMe)2][FeIIICl 4] is predicted to be strongly spin polarized from density functional calculations; and second, it exhibits pressure-induced magnetic regions and magnetic suppression.