112068-77-6Relevant articles and documents
Nonanuclear Oxide-Bridged Manganese Complex. Preparation, Structure, and Magnetic Properties of (salH2 = Salicylic Acid; pyr = Pyridine)
Christmas, Cheryl,Vincent, John B.,Chang, Hsiu-Rong,Huffman, John C.,Christou, George,Hendrickson, David N.
, p. 823 - 830 (1988)
The preparation of a mixed-valence nonanuclear manganese complex with mixed salicylate/benzoate/pyridine ligation is described.Treatment of with 3 equiv of salicylic acid (salH2) in CH3CN leads to the formation of (5), where pyr is pyridine.Complex 5 crystallizes in the monoclinic space group C2/c with, at -155 deg C, a=17.625(13) Angstroem, b=38.314(35) Angstroem, c=19.886(16) Angstroem, β=99.17(4) deg, and Z=4.The stucture was solved and refined with a total of 3168 unique reflections with F>2.33?(F).Final values of conventional discrepancy indices R and Rw are 9.70 and 9.92percent, respectively.The structure consists of two butterfly-like units, containing octahedral MnIII ions, linked together by a bridging Mn(sal)4 central unit.The latter contains an eight-coordinate MnII ion and is the site of a crystallographic C2 axis relating the halves of the molecule.The sal2- groups linking the MnII and units have a rare μ3-η3-bridging mode; peripheral ligation to the complete molecule is provided by eight μ2-PhCOO-, four terminal pyr, and two μ2-salH- groups, employing only their carboxylate functions with the phenoxide oxygen atoms protonated and not bound to a manganese ion.The complex possesses an average metal oxidation state of +2.89 and is a rare example of a discrete high-nuclearity manganese species.The results of solid-state magnetic susceptibility studies in the temperature range 300.9-5.0 K are described.The effective magnetic moment per molecule (μeff) gradually decreases from a value of 11.82 μB at 300.9 K to a value of 5.83 μB at 5.0 K.The derivation of a theoretical model to account for the intramolecular magnetic exchange interactions in 5 by the Kambe vector coupling approach is described.Least-squares fitting of the susceptibility data to the model gives exchange parameters for the butterfly-like units of J=-26.2 cm-1 for the (μ-O)2MnIII interaction, J=-11.2 cm-1 for the hinge - wing-tip (μ-O)2MnIII2 interaction, and J=-0.97 cm-1 for the eight MnII...MnIII interactions.Of the 209 725 states of 5, the ground state is found to be a S=3/2 state, with more than 3000 states found within 150 cm-1 of the ground state.
