CRYSTAL-STRUCTURE AND METAMAGNETIC BEHAVIOR OF THE FERRIMAGNETIC CHAIN COMPOUND MNCU(OPBA)(H2O)(2)-CENTER-DOT-DMSO (OPBA=O-PHENYLENEBIS(OXAMATO) AND DMSO=DIMETHYL SULFOXIDE)

The title compound has been synthesized, and its crystal structure has been solved. It crystallizes in the triclinic system, space group <P( 1)over bar>; the lattice parameters are a = 7.300(3) Angstrom, b = 10. 734(3) Angstrom, c 12.585(6) Angstrom, alpha = 68.43(3)degrees, beta = 84.92(4)degrees, gamma = 73.97(3)degrees, and Z = 2. The structure co nsists of oxamato-bridged (MnCuII)-Cu-II chains running along the b ax is with a Mn- - -Cu intrachain separation of 5.387(1) Angstrom. The ch ains pack above each other along the a axis with Mn- - -Mn = 5.030(1) Angstrom as the shortest metal. . .metal interchain separation, formin g bimetallic layers. These are separated by noncoordinated DMSO molecu les along the c axis. The Mn(II) ion is in distorted octahedral enviro nment, with two water molecules in trans positions; the Cu(II) ion is in planar environment. The magnetic susceptibility and the magnetizati on of the compound have been investigated. The T-chi M versus T plot s hows the minimum at 130 K characteristic of the one-dimensional ferrim agnetism, and a maximum at 8 K, related to a three-dimensional antifer romagnetic ordering at T-N = 5 K. The intrachain interaction parameter has been found as J(MnCu)=-32.1 cm(-1) (H=-J(MnCu)Sigma(i)S(Mn,i).S-C u,S-i) The field dependence of the magnetization has revealed a field- induced transition from an antiferromagnetic to a ferromagnetic-like s tate. A magnetic field of 5 kOe is sufficient to overcome the weak int erchain antiferromagnetic interactions, so that the compound may be de scribed as a metamagnet built from ferrimagnetic chains.