Structure and magnetic properties of two cyanide-bridged one-dimensional M–CuII (M = FeIII or FeII) bimetallic assemblies from ferricyanide and CuN42+ (N4 = 1,4,8,11-tetraazacyclotetradecane and N,N′-bis(2-pyridylmethylene)-1,3-propanediamine) building blocks

Abstract

Two bimetallic assemblies K[Cu(cyclam)][Fe(CN)₆]·4H₂O 1 and [Cu(L)][Cu(L¹)][Fe(CN)₆]·6.5H₂O 2 (cyclam = 1,4,8,11-tetraazacyclotetradecane; L = N,N′-bis(2-pyridylmethylene)-1,3-propanediamine and L¹ = N-2-pyridylmethylene-1,3-propanediamine) have been prepared from the reaction of [Fe(CN)₆]³⁻ and the precursors [Cu(cyclam)]²⁺ and [Cu(L)]²⁺, respectively, and their structure and magnetic properties studied. The structure of 1 consists of polymeric zigzag chains of alternating [Fe(CN)₆]³⁻ and [Cu(cyclam)]²⁺ units, K⁺ cations and crystal water molecules. In the crystals the chains are linked by CN–K–NC interactions, to form a two-dimensional layer structure. Magnetic measurements show a weak ferromagnetic intrachain interaction based on the strict orthogonality of the magnetic orbitals of the Fe^III and Cu^II. In the structure of 2 each [Cu(L¹)]²⁺ unit is bonded to centrosymmetric [Fe(CN)₆]⁴⁻ and [Cu(L)Fe(CN)₆Cu(L)] units through two cis bridging cyanide ligands. Owing to the symmetry, a unique one-dimensional zigzag chain structure is formed through trans bridging cyanide ligands of the two crystallographically non-equivalent [Fe(CN)₆]⁴⁻ groups. In the course of the reaction the [Fe(CN)₆]³⁻ ion undergoes a reduction to [Fe(CN)₆]⁴⁻ whereas the [Cu(L)]²⁺ ion partly hydrolyses to [Cu(L¹)]²⁺. Compound 2 is essentially paramagnetic within the chain.