High Spin Molecules: Unusual Magnetic Susceptibility Relaxation Behavior of a Dodecanuclear Manganese Aggregate in Two Oxidation States

Abstract The mixed valence dodecanuclear complex [Mn12O12(O2CEt) 16(H2O)3 may be reduced by one electron to give (PPh4)[Mn12O12(O2CEt)16(H2O)4. Reduction of the complex occurs at one MnIII ion to give an unusual trapped-valence MnIIMnIII 7MnIV 4 complex. This formulation is supported by X-ray crystallography at both low temperature and room temperature. DC (2.0–4.0K, 20–50 kG fields) and AC (2.0–30 K, 1.0 and 0.0050G fields, 25–1000 Hz frequencies) magnetic susceptibility measurements indicate ground states of S=9 and S=19/2 for the neutral and reduced species, respectively. (PPh4)[Mn12O122(O2CEt)16(H2O)4 exhibits an out-of-phase component of the AC magnetic susceptibility (X M) which has a frequency dependent maximum. This is a very unusual property for a discrete molecular species to display. The neutral analog shows two peaks in the X M vs. T plot. DC measurements also show the presence of prominent hysteresis loops, and field-cooled and zero-field-cooled magnetization data are not superimposed at low ...