We present the synthesis, crystal structure, and temperature and field dependence of the magnetic properties of a new molecule-based magnet, [Co(hfac)2].BNO* (1), where hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato and BNO* is the chiral triplet bis(nitroxide), 1,3-bis(N-tert-butyl-N-oxylamino)-5-{1'-methyl-1'-[2' '-(S)-methylbutoxy]ethyl}benzene. The presence of enantiomer-pure BNO induces the formation of chiral one-dimensional chains that are packed parallel to each other in the noncentrosymmetric P1 space group. 1 exhibits four magnetic ground states: paramagnetic; antiferromagnetic; forced ferrimagnetic; field-induced metastable ferrimagnetic. In the paramagnetic state (T > 20 K), it presents short-range antiferromagnetic interaction between Co ion and nitroxide radical and has a minimum of chimT value at 220 K. The Weiss temperature estimated in the temperature range 220-300 K is found to be -89.9 K. At 20 K (TN), an antiferromagnetic long-range ordering is established. In the temperature range 4 K < T < 20 K, the isothermal magnetization curve show a spin-flip transition to the forced ferrimagnetic state at around 850 Oe. Below 4 K, this compound enters into a field-induced ferrimagnetic state, which is metastable and stabilized by the Ising character of the Co ion. In the low-temperature phase, the material becomes a very hard magnet with wide hysteresis loop whose coercive field reaches 25 kOe at 2 K. The magnetic phase diagram based on these magnetic data is presented.
We measured angular dependences of single-crystal magnetization for the chiral structural molecule-based metamagnet [Mn(hfac)2]·BNO* (1). This crystal shows remarkable crystal direction dependences of spin flip transition in all crystallographic a, b, and c axes and the transitions are observed at different critical magnetic fields (H || a: 640 Oe, H || b: 1000 Oe, and H || c: 1250 Oe at 2 K). These results mean that 1 has independent antiferromagnetic multi-sublattices. We calculated its possible magnetic structure from magnetic data and constructed magnetic structural model.
Benzo furano[2´,3´:1,2][60]fullerene derivatives were derived from the reaction of fullerene monoepoxide C60O with phenol compounds in the presence of BF3•OEt2 as a Lewis acid catalyst in a chlorobenzene solution. We prepared various indolino[60]fullerene- and benzo furano[60]fullerene derivatives comprising either an electron-donating or a withdrawing substituent on the indoline and benzo furan moieties. The reduction potentials of these compounds depended on the type of substituent effect; first, linear correlations existed between the substituent constants and their first reduction potentials, and second, the first reduction potentials remarkable reduced due to the influence of the 4´-MeO groups.
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