| Popis: |
A series of (Cu, Mn, Cu) complexes have been prepared and characterized. They may be described by the overall formula (CuL)(2)Mn.xB where L stands for the deprotonated form of N-(4-methyl-6-oxo-3-azahept-4-enyl)oxamic acid and B for respectively H(2)O (with x = 5, 4.5, 3, 1), (CH(3))(2)SO (with x = 2), and C(5)H(5)N (with x = 4). The crystal and molecular structures of (CuL)(2)Mn.2(CH(3))(2)SO have been solved. The crystals are monoclinic, space group P2(1)/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)(2)Mn.4.5H(2)O confirms that a magnetic phase transition occurs at low temperature and that, below T(c) = 37 K, the complex displays weak ferromagnetism. |
