DITHIOOXALATO(DTO)-BRIDGED BIMETALLIC ASSEMBLIES (NPR4[MCR(DTO)3)X (M=FE, CO, NI, ZN, NPR4=TETRAPROPYLAMMONIUM ION) - NEW COMPLEX-BASED FERROMAGNETS

The reaction of potassium calcium tris(dithiooxalato)chromate(III) hexahydrate KCa[Cr(dto)3].6H2O, a metal(II) salt and a tetrapropylammonium bromide (NPr4Br) in aqueous methanol forms bimetallic assemblies {NPr4[MCr(dto)3]}x (M=Fe (1), Co (2), Ni (3), Zn (4)), where the dto group bridges Cr(III) and M(II) ions through the sulfur atoms to Cr(III) and through the oxygen atoms to M(II) to provide an alternate array of Cr(III) and M(II) ions. The magnetic susceptibility data for 1-3 in the temperature range 5-300 K obey the Curie Weiss law (chi(M)-1 = (T - theta)/C) with a positive Weiss constant (+18 K for 1, +24 K for 2, and +41 K for 3), and the effective magnetic moments increase with decreasing temperature. The magnetization studies (field-cooled magnetization, remnant magnetization, and zero-field cooled magnetization) reveal the ferromagnetic phase transition at T(C) = 8, 16, and 23 K for 1, 2, and 3, respectively. The assembly 4 shows paramagnetic behavior in the temperature range of 5-300 K.