A Family of Manganese Rods: Syntheses, Structures, and Magnetic Properties

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Abstract
The reaction of the mixed-valent metal triangles [Mn3O(O2CR)6(py)3] (R = CH3, Ph, C(CH3)3) with the tripodal ligands H3thme (1,1,1-tris(hydroxymethyl)ethane) and H3tmp (1,1,1-tris(hydroxymethyl)propane) in MeCN, produces a family of manganese rodlike complexes whose structures are all derived from a series of edge-sharing triangles. Variable temperature direct current (dc) magnetic susceptibility data were collected for all complexes in the 1.8−300 K temperature range in fields up to 7.0 T. Complex 1, [Mn12O4(OH)2(PhCOO)12(thme)4(py)2], has an S = 7 ground state with the parameters g = 1.98 and D = −0.13 K. Complex 2, [Mn8O4((CH3)3CCO2)10(thme)2(py)2] has a ground state of S = 6, with g = 1.81 and D = −0.36 K. Complex 3, [Mn7O2(PhCO2)9(thme)2(py)3], has a spin ground states of S = 7 with the parameters g = 1.78 and D = −0.20 K. The best fit for complex 4, [Mn6((CH3)3CCO2)8(tmp)2(py)2], gave a spin ground state of S = 3 with the parameters g = 1.73 and D = −0.75 K, but was of poorer quality than that normally obtained. The presence of multiple Mn2+ ions in the structure of 4 leads to the presence of low-lying excited states with energy levels very close to the ground state, and in the case of complex 5, [Mn6(CH3CO2)6(thme)2(H2tea)2], no satisfactory fit of the data was obtained. DFT calculations on 4 and 5 indicate complexes with spin ground states of S = 4 and S = 0 respectively, despite their topological similarities. Single-crystal hysteresis loop and relaxation measurements show complex 1 to be a SMM.