LAYERED HYDROGENSELENITES .2. SYNTHESIS, STRUCTURE STUDIES AND MAGNETIC-PROPERTIES OF A NOVEL SERIES OF BIMETALLIC HYDROGENSELENITES - [CU(HSEO3)(2)MCL(2)(H2O)(4)], M(II)=MN,CO,NI,CU,ZN

A new family of bimetallic hydrogenselenites [Cu(HSeO3)(2)Cu(x)M(1-x)Cl(2)(H2O)(4)], with M(II)=Mn, Co, Ni, Cu, Zn and x depending mainly on the nature of the second cation M, has been prepared. The crystal structure of [Cu(HSeO3)(2)MnCl2(H2O)(4)] has been determined. It crystallizes in the orthorhombic system, space group Pnma, with a=9.125(2), b=18.178(3), c=7.187(2) Angstrom, and V=1192.4(4) Angstrom(3), Z=4. This structure is three-dimensional but it may be described as a bidimensional structure made of layers, parallel to the (010) plane, which contain copper atoms and HSeO3- anions. The sheets are similar to those obtained for the [Cu(HSeO3)(2)] compound. In this family, the sheets are interconnected by [(Cu(x)M(1-x))Cl-2(H2O)(4)] entities. Magnetic measurements reveal the occurrence of weak ferromagnetism at low temperature (T=similar to 10-20 K) for almost all compounds except [Cu(HSeO3)(2)]. A tentative explanation will be offered for this peculiar property.