Abstract
The electronic structures of the compounds K[(5-Brsalen)2(H2O)2-Mn2MIII(CN)6] ·2H2O (MIII = CoIII, CrIII, FeIII) have been determined by inelastic neutron scattering (INS) and magnetic susceptibility studies, revealing the manganese(III) single-ion anisotropy and exchange interactions that define the low-lying states of the Mn-MIII-Mn trimeric units. Despite the presence of an antiferromagnetic intertrimer interaction, the experimental evidence supports the classification of both the Cr(III) and Fe(III) compounds as single-molecule magnets. The value of 17(2) cm-1 established from AC susceptibility measurements for a spin-reversal barrier of K[(5-Brsalen)2(H2O)2-Mn2Cr(CN)6]·2H2O may be readily rationalized in terms of the energy level diagram determined directly by INS. AC susceptibility measurements on samples of K[(5-Brsalen)2(H2O)2-Mn2Fe(CN)6]·2H2O are contrary to those previously reported, exhibiting but the onset of peaks below temperatures of 1.8 K at oscillating frequencies in the range of 100-800 Hz. INS measurements reveal an anisotropic ferromagnetic manganese(III)-iron(III) exchange interaction, in accordance with theoretical expectations based on the unquenched orbital angular momentum of the [Fe(CN)6]3- anion, giving rise to an Ms similar to +/-9/2 ground state, isolated by similar to 11.5 cm-1 from the higher-lying levels. The reported INS and magnetic data should now serve as a benchmark against which theoretical models that aim to inter-relate the electronic and molecular structure of molecular magnets should be tested.
Original language | English |
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Journal | Inorganic Chemistry |
Volume | 48 |
Issue number | 1 |
Pages (from-to) | 128-137 |
ISSN | 0020-1669 |
DOIs | |
Publication status | Published - 2009 |
Externally published | Yes |