| Abstract
| - We report a new theoretical model that accounts for the unusual magnetic properties of thecyanide cluster {[MnII(tmphen)2]3[MnIII(CN)6]2} (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline). Themodel takes into account (1) the spin−orbit interaction, (2) the trigonal component of the crystal field actingon the ground-state cubic 3T1() terms of the apical Mn(III) ions, and (3) the isotropic contribution to theexchange interaction between Mn(III) and Mn(II) ions. The ground state of the cluster was shown to be thestate with the total angular momentum projection |MJ| = 15/2; the energies of the low-lying levels obtainedfrom this treatment increase with decreasing |MJ| values, a situation that leads to a barrier for the reversalof magnetization (Ueff ≈ 30 cm-1). The new model explains the recently discovered single-molecule magnetbehavior of the {[MnII(tmphen)2]3[MnIII(CN)6]2} in contrast to the traditional approach that takes into accountonly the ground-state spin (S) and a negative zero-field splitting parameter (DS< 0).
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