ic301764t_si_002.cif (25 kB)
Synthesis, Structure, and Spectroscopic and Magnetic Characterization of [Mn12O12(O2CCH2But)16(MeOH)4]·MeOH, a Mn12 Single-Molecule Magnet with True Axial Symmetry
dataset
posted on 2013-01-07, 00:00 authored by Christos Lampropoulos, Muralee Murugesu, Andrew
G. Harter, Wolfgang Wernsdofer, Stephen Hill, Naresh S. Dalal, Arneil P. Reyes, Philip L. Kuhns, Khalil A. Abboud, George ChristouThe synthesis and properties are reported of a rare example
of a Mn12 single-molecule magnet (SMM) in truly axial symmetry
(tetragonal, I4̅). [Mn12O12(O2CCH2But)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-resolved peaks were observed, which
yielded hyperfine and quadrupole splitting at three distinct sites.
However, observation of a slight asymmetry in the Mn4+ peak
was detectable, suggesting a possible decrease in the local symmetry
of the Mn4+ site. Spin–lattice (T1) relaxation studies were performed on single crystals
of 3·MeOH down to 400 mK in an effort to approach
the quantum tunneling regime, and fitting of the data using multiple
functions was employed. The present work and other recent studies
continue to emphasize that the new generation of truly high-symmetry
Mn12 complexes are better models for thorough investigation
of the physical properties of SMMs than their predecessors such as 1.
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satellite peakshysteresis loopsquadrupole splittingfield orientationTrue Axial SymmetryThe synthesis10 ground statequantum tunnelingresonance spectra400 mKACSMM360 GHzfield valuesquantum tunneling regimeMn 12 environmentsMn 12 familyNMRDCMn 12Ocarboxylate substitutionmagnetization stepsMagnetic Characterization
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