Superparamagnetic-like properties of the valence-trapped MnIIMnIII7MnIV4 anion in the salt (PPh4)[Mn12O12(O2CEt)16(H2O)4]

Abstract

Reduction of the 8Mn^III,4Mn^IV complex [Mn₁₂O₁₂(O₂CEt)₁₆(H₂O)₃] with PPh₄l in CH₂Cl₂ leads to isolation of (PPh₄)[Mn₁₂O₁₂(O₂CEt)₁₆(H₂O)₄](3) whose crystal structure shows that the added electron is localized on a formerly Mn^III ion to give a trapped-valence Mn^II,7Mn^III,4Mn^IV situation; DC and AC magnetic susceptibility studies show that 3 has an S= 19/2 ground state and that it displays a superparamagnet-like non-zero, frequency-dependent, out-of-phase response in the AC susceptibility behaviour that is extremely unusual for a molecular species and unique for an ionic species.