Towards designing Mn_4 molecules with strong intramolecular exchange coupling

概要

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Distorted cubane Mn^<4+>Mn^<3+>_3 single-molecule magnets (SMMs) have been studied by first-principles calculations, i.e. [Mn_4L_3X(OAc)_3(dbm)_3] (L=O; X=F, Cl, and Br; dbmH=dibenzoyl-methane). It was shown in our previous paper (Tuan et al 2009 Phys. Chem. Chem. Phys. 11 717) that the ferrimagnetic structure of Mn^<4+>Mn^<3+>_3 SMMs is dominated by π type hybridization between the d_z2 orbitals at the three high-spin Mn^<3+> ions and the t_<2g> orbitals at the Mn^<4+> ion. To design new Mn^<4+>Mn^<3+>_3 molecules having much more stable ferrimagnetic states, one approach is suggested. This involves controlling the Mn^<4+>-L-Mn^<3+> exchange pathways by rational variations in ligands to strengthen the hybridization between the Mn ions. Based on this method, we succeed in designing new distorted cubane Mn^<4+>Mn^<3+>_3 molecules having Mn^<4+>-Mn^<3+> exchange coupling of about 3 times stronger than that of the synthesized Mn^<4+>Mn^<3+>_3 molecules. These results give some hints regarding experimental efforts to synthesize new superior Mn^<4+>Mn^<3+>_3 SMMs.
2011-03-08