| Abstract |
The direct synthesis approach, namely one-pot reaction of metal powders and ammonium salt with a methanol solution of a polydentate Schiff base (H2L) formed in situ from salicylaldehyde and ethanolamine, has been successfully used for the preparation of the new heterometallic compounds [Cu3Mn (L)(4)(CH3OH)3](I)3 (1), [Cu3Mn(L)(4)(CH3OH)(3)(H2O)] NCS center dot H2O (2), [Cu3Mn(L)(4)(CH3OH)(H2O)(2.55)] Br center dot 0.45H(2)O (3) and [Cu3Mn(L)(4)(H2O)(3.4)]BF4 center dot 0.6H(2)O (4). Crystallographic analysis revealed that 1-4 are based on the tetranuclear core \Cu-3(II) Mn-III(mu 3-O)(4)\ where the metal centres are joined by the oxygen bridges of Schiff base ligands forming a cube-like arrangement. The novel heterometallic compound [Cu3Mn(L)(4)(CH3OH)(3)](2) [Mn(NCS)(4)]center dot 2CH(3)OH (5) has been obtained by the building block approach using the reaction of [Cu(HL)(2)] with manganese acetate and NH4NCS in methanol. The crystal structure of 5 revealed the \Cu-3(II) Mn-III(mu-O) (2)(mu(3)-O)(2)\ metal core which can be viewed as a double open cube. In spite of a similar \Cu3MnO4\ atom set in the cores of 1-5, the complexes show rather different molecular structures and significantly differ by the number and combinations of coordinated CH3OH/H2O solvent molecules. Variable-temperature (2-300 K) magnetic susceptibility along with variable-field magnetization measurements of 1-5 showed a decrease of the effective magnetic moment value at low temperature, indicative of the antiferromagnetic coupling of medium size (-55 to -22 cm(-1)). For these systems resembling a compressed prism the coupling constant in walls J4 correlates with the averaged bonding angles in walls alpha: J4 vs. a develops approximately according to a straight line. |
