Distorted Mn^IVMn^III₃ Cubane Complexes as Single-Molecule Magnets

TLDR

The study discusses factors determining single‑molecule magnet behavior and notes that these Mn₄ complexes are only the second class of molecules with sufficient magnetic anisotropy to act as single‑molecule magnets. Ac magnetic susceptibility measurements on six distorted MnIVMnIII₃O₃X cubane complexes reveal S = 9/2 ground states with axial zero‑field splitting (D ≈ –0.27 to –0.38 cm⁻¹) that produce out‑of‑phase signals indicative of slow magnetization relaxation, confirming that each isolated molecule behaves as a single‑molecule magnet.

Abstract

Alternating current (ac) magnetic susceptibility data are presented for six distorted cubane complexes of the composition [MnIVMnIII3O3X]. Each of these complexes has a well isolated S = 9/2 ground state. There is zero-field splitting (ZFS) in the ground states where D, the axial ZFS parameter, is found to be in the range of −0.27 to −0.38 cm-1. As a result of the big spin ground state and appreciable magnetic anisotropy, an out-of-phase ac magnetic susceptibility signal is seen for each of the six Mn4 complexes. The out-of-phase ac susceptibility signal reflects slow magnetization relaxation which is taken to indicate that individual molecules are acting as magnets. Alternating current susceptibility data are presented for a frozen glass of one of the Mn4 complexes to confirm that the out-of-phase ac signal is associated with isolated molecules. The factors that influence whether a given complex can function as a single-molecule magnet are described. The above Mn4 complexes represent only the second type of molecules that exhibit enough magnetic anisotropy to function as single-molecule magnets.