An original 1D Cu–Co heterometallic compound: synthesis, structure and magnetic properties

Abstract

A novel heterobimetallic system, 1∞[LCuIICoII(NCS)2] (1), was obtained by reacting the neutral mononuclear complex [LCu] with cobalt(II) acetate in the presence of potassium thiocyanate (L is the dianion of the Schiff base resulting from the 2 ∶ 1 condensation of 3-methoxysalicylaldehyde with 1,3-propanediamine). The crystallographic investigation of 1 reveals a one-dimensional alternating zig-zag chain-like structure, made of dinuclear {LCuCo} units linked by thiocyanate bridges. The copper(II) ion is pentacoordinate to the N2O2 donor set of the Schiff base ligand in the basal plane, with the apical position occupied by the sulfur atom. The cobalt ion displays a strongly distorted (4 + 2) octahedral geometry. The distance between the phenoxo-bridged metal ions is 3.149(1) Å. The Cu⋯Co distance for the NCS− bridged ions is equal to 6.125(1) Å. The magnetic properties of 1 were investigated in the temperature range 2–300 K and they are explained by a strong antiferromagnetic Cu(II)–Co(II) exchange interaction through the phenoxo bridges and a weak ferromagnetic Cu(II)–Co(II) interaction through the thiocyanato bridges. Several theoretical models are proposed to fit the magnetic data of 1, the most appropriate one being the full matrix diagonalization for a closed-chain of four dinuclear units [CuIICoII], taking into account two different exchange parameters and a D term, which yielded the following results: J = −101.2 cm−1, j = 2.8 cm−1, D = −0.11 cm−1, g = 2.38.