Synthesis, Structure, and Magnetic Properties of Mn(salpn)N_3,a Helical Polymer, and Fe(salpn)N₃, a Ferromagnetically Coupled Dimer (salpnH₂=<i>N</i>,<i>N</i>‘-bis(Salicylidene)-1,3-diaminopropane)

Abstract

The preparation, crystal structures, and variable temperature magnetic susceptibility data are presented for two azido-bridged Schiff base complexes of Mn(III) and Fe(III). Mn(salpn)N(3) (1), where salpn is the dianion of N,N'-bis(salicylidene)-1,3-diaminopropane, crystallizes in the orthorhombic system, space group Pna2(1), with a = 11.947(2) Å, b = 11.818(2) Å, c = 11.227(5) Å, and Z = 4. Fe(salpn)N(3) (2) crystallizes in the monoclinic system, space group P2(1)/c, with a = 10.199(7) Å, b = 14.081(6) Å, c = 12.017(3) Å, beta = 105.19(3) degrees, and Z = 4. In 1, salpn coordinates in the equatorial mode, with two azide ions coordinating in axial positions. The azide ions act as "end-to-end" (&mgr;-(1,3)) bridges, leading to an infinite helical chain propagating along the crystallographic c axis. In striking contrast, 2 has a dimeric structure in which the Schiff base adopts a cis-octahedral coordination mode. The dimer is held together by two "head-on" (&mgr;-(1,1)) bridging azide ions. The polymeric compound, 1, is weakly antiferromagnetic (J = -4.03 cm(-)(1), H(ex) = -2J summation operatorS(i)()S(i)()(+1)), while 2 is weakly ferromagnetic (J = 0.76 cm(-)(1), H(ex) = -2JS(1)S(2)).