Synthesis, Structure, and Spectroscopic and Magnetic Characterization of [Mn12O12(O2CCH2Bu t)16(MeOH)4]·MeOH, a Mn12 Single-Molecule Magnet with True Axial Symmetry

*S Supporting Information ABSTRACT: The synthesis and properties are reported of a rare example of a Mn12 single-molecule magnet (SMM) in truly axial symmetry (tetragonal, I4 ̅). [Mn12O12(O2CCH2Bu t)16(MeOH)4]·MeOH (3·MeOH) was synthesized by carboxylate substitution on [Mn12O12(O2CMe)16(H2O)4]·2MeCO2H·4H2O (1). The complex was found to possess an S = 10 ground state, as is typical for the Mn12 family, and displayed both frequency-dependent out-of-phase AC susceptibility signals and hysteresis loops in single-crystal magnetization vs DC field sweeps. The loops also exhibited quantum tunneling of magnetization steps at periodic field values. Single-crystal, high-frequency electron paramagnetic resonance spectra on 3·MeOH using frequencies up to 360 GHz revealed perceptibly sharper signals than for 1. Moreover, careful studies as a function of the magnetic field orientation did not reveal any satellite peaks, as observed for 1, suggesting that the crystals of 3 are homogeneous and do not contain multiple Mn12 environments. In the single-crystal 55Mn NMR spectrum in zero applied field, three well