Two binuclear cyanide-bridged Cr(III)-Mn(III) complexes based-on [Cr(2,2’-bipy)(CN)4]- building block: synthesis, crystal structures and magnetic properties

Abstract

Tetracyanide building block [Cr(2,2’-bipy)(CN)₄]^- and two bicompartimental Schiff-base based manganese(III) compounds have been employed to assemble cyanide-bridged heterometallic complexes, resulting in two cyanide-bridged Cr^III-Mn^III complexes: [Mn(L¹)(H₂O)][Cr(2,2’-bipy)(CN)₄]·CH₃OH·2.5H₂O (1) and [Mn(L²)(H₂O)][Cr(2,2’-bipy)(CN)₄]·CH₃OH·3H₂O (2) (L¹ = N,N'-(1,3-propylene)-bis(3-methoxysalicylideneiminate), L² = N,N'-ethylene-bis(3-ethoxysalicylideneiminate)). Single X-ray diffraction analysis shows their similar cyanide-bridged binuclear structures, in which the cyanide precursor acting as monodentate ligand connects the manganese(III) ion. The binuclear complexes are self-complementary through coordinated aqua ligand and the free O₄ compartment from the neighboring complex, giving H-bond linking dimer structure. Investigation over magnetic properties reveals the antiferromagnetic magnetic coupling between the cyanide-bridged Cr(III) and Mn(III) ions. A best-fit to the magnetic susceptibilities of these two complexes leads to the magnetic coupling constants J = -5.95 cm^-1, j = -0.61 cm^-1 (1) and J = -4.15 cm^-1, j = -0.57 cm^-1 (2), respectively.