Dipole Switching by Intramolecular Electron Transfer in Single-Molecule Magnetic Complex [Mn12O12(O2CR)16(H2O)4]

We study intramolecular electron transfer in the single-molecule magnetic complex [Mn12O12(O2CR)16 (H2O)4] for R = -H, -CH3, -CHCl2, -C6H5, -C6H4F ligands as a mechanism for switching of the molecular dipole moment. Energetics are obtained using the density functional theory (DFT) with onsite Coulomb energy correction (DFT+U). Lattice distortions are found to be critical for localizing an extra electron on one of the easy sites on the outer ring in which localized states can be stabilized. We find that the lowest energy path for charge transfer is for the electron to go through the center via superexchange mediated tunneling. The energy barrier for such a path ranges from 0.4 meV to 54 meV depending on the ligands and the isomeric form of the complex. The electric field needed to move the charge from one end to the other, thus reversing the dipole moment, is 0.01 - 0.04 V/Å.