Wheel-Shaped [Mn12] Single-Molecule Magnets

The reaction of [Mn12O12(O2CCH3)16(H2O)4]·4H2O·2CH3COOH with n-methyldiethanol amine (H2mdea), n-ethyldiethanol amine (H2edea), or n-butyldiethanol amine (H2bdea) leads to the formation of wheel-shaped MnIII 6MnII 6 complexes with the general formula [Mn12(R)(O2CCH3)14] (1, R = mdea; 2, R = edea; and 3, R = bdea). Complex 1 crystallizes in the triclinic space group P1̄, whereas complex 3 crystallizes in the monoclinic space group C 2/ c . Complex 1a has the same molecular structure as complex 1 but crystallizes in the monoclinic space group P21 /n . Complex 3a has the same molecular structure as complex 3 but crystallizes in the triclinic space group P1̄. Variable-temperature magnetic susceptibility data collected for complexes 1, 2, and 3 indicate that antiferromagnetic exchange interactions are present. The spin ground states of complexes 1, 2, and 3 were determined by fitting variable-field magnetization data collected in the 2−5 K temperature range. Fitting of these data yielded the spin ground-state parameters of S = 8, g = 2.0, and D = −0.47 cm-1 for complex 1; S = 8, g = 2.0, and D = −0.49 cm-1 for complex 2; and S = 8, g = 2, and D = −0.37 cm-1 for complex 3. The ac magnetic susceptibility data were measured for complexes 1, 2, and 3 at temperatures between 1.8 and 10 K with a 3 G ac field oscillating in the range 50−1000 Hz. Slow kinetics of magnetization reversal relative to the frequency of the oscillating ac field were observed as frequency-dependent out-of-phase peaks for complexes 1, 2, and 3, and it can be concluded that these three complexes are single-molecule magnets.