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) hex ahydrate KCa[Cr(dto)3].6H2O, a metal(II) salt and a tetrapropylammoniu m bromide (NPr4Br) in aqueous methanol forms bimetallic assemblies {NP r4[MCr(dto)3]}x (M=Fe (1), Co (2), Ni (3), Zn (4)), where the dto grou p bridges Cr(III) and M(II) ions through the sulfur atoms to Cr(III) a nd 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 th e 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, an d +41 K for 3), and the effective magnetic moments increase with decre asing temperature. The magnetization studies (field-cooled magnetizati on, 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 t he temperature range of 5-300 K.