Towards designing Mn4 molecules with strong intramolecular exchange coupling

Anh Tuan Nguyen and Hieu Chi Dam

Abstract

Distorted cubane Mn⁴⁺Mn³⁺₃ single-molecule magnets (SMMs) have been studied by first-principles calculations, i.e. [Mn₄L₃X(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 Mn⁴⁺Mn³⁺₃ SMMs is dominated by π type hybridization between the d_z² orbitals at the three high-spin Mn³⁺ ions and the t_2g orbitals at the Mn⁴⁺ ion. To design new Mn⁴⁺Mn³⁺₃ molecules having much more stable ferrimagnetic states, one approach is suggested. This involves controlling the Mn⁴⁺–L–Mn³⁺ 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 Mn⁴⁺Mn³⁺₃ molecules having Mn⁴⁺–Mn³⁺ exchange coupling of about 3 times stronger than that of the synthesized Mn⁴⁺Mn³⁺₃ molecules. These results give some hints regarding experimental efforts to synthesize new superior Mn⁴⁺Mn³⁺₃ SMMs