Magnetic Properties of a Series of Trinuclear Complexes (CuL)<sub>2</sub>Mn·<i>x</i>B (L Representing the Deprotonated Form of <i>N</i>-(4-Methyl-6-oxo-3-azahept-4-enyl)oxamic Acid and B Representing Respectively H<sub>2</sub>O (<i>x</i> = 5, 4.5, 3, 1), (CH<sub>3</sub>)<sub>2</sub>SO (<i>x </i>= 2), and C<sub>5</sub>H<sub>5</sub>N (<i>x </i>= 4)). Crystal and Molecular Structure of (CuL)<sub>2</sub>Mn·2(CH<sub>3</sub>)<sub>2</sub>SO
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A series of (Cu, Mn, Cu) complexes have been prepared and characterized. They may be described by the overall formula (CuL)2Mn·xB where L stands for the deprotonated form of N-(4-methyl-6-oxo-3-azahept-4-enyl)oxamic acid and B for respectively H2O (with x = 5, 4.5, 3, 1), (CH3)2SO (with x = 2), and C5H5N (with x = 4). The crystal and molecular structures of (CuL)2Mn·2(CH3)2SO have been solved. The crystals are monoclinic, space group P21/n with cell constants a = 8.362(2) Å, b = 14.426(3) Å, c = 24.442(6) Å, and Z = 4. In each (Cu, Mn, Cu) molecular unit the central Mn(II) ion is bridged to two copper(II) ions through two oxamato groups. Short intermolecular Cu···Cu distances lead to the formation of a chain-like packing pattern running parallel to the c-axis. Magnetic susceptibility measurements have been performed for the six complexes. Five complexes display the same behavior which corresponds to the occurrence of antiferromagnetic Cu−Mn interactions within isolated trinuclear units. The J values are between −29.4(2) and −33.8(5) cm-1. Surprisingly the field and temperature dependence of the magnetization for (CuL)2Mn·4.5H2O confirms that a magnetic phase transition occurs at low temperature and that, below Tc = 37 K, the complex displays weak ferromagnetism.
