Synthesis, structure, and magnetic properties of cyanide-bridged low-dimensional heterometallic FeIII–MnII complexes

Abstract

With trans-dicyanideiron(III) precursor K[Fe(salen)(CN)₂]·CH₃OH (1) (H₂salen = N,N′-bis(salicyl)ethylenediamine) as a building block, four new cyanide-bridged heterometallic Fe^III–Mn^II complexes {[Fe(salen)(CN)₂]₂[Mn(bipy)₂]}·CH₃OH·2H₂O (2), {[Fe(salen)(CN)₂]₂[Mn(phen)₂]}·CH₃OH (3), and {[Fe(salen)(CN)₂][Mn(L)]}ClO₄·CH₃OH [L = L^a (4) and L^b (5)] have been successfully assembled. Single X-ray diffraction analyses reveals the trinuclear Fe^III₂Mn^II nature of complexes 2 and 3 comprised of one [Mn(bipy)₂]²⁺/[Mn(phen)₂]²⁺ and two [Fe(salen)(CN)₂]⁻ units, and the one-dimensional cyanide-bridged cationic polymeric single chain nature of complexes 4 and 5 consisting of alternating units of [Mn(L)]²⁺ (L = L^a and L^b) and [Fe(salen)(CN)₂]⁻ with free ClO₄⁻ as balanced anions. Investigations into the magnetic properties of these four heterometallic cyanide-bridged Fe^III–Mn^II complexes reveals the overall antiferromagnetic interaction between neighbouring Fe(III) and Mn(II) ions through the bridging cyanide group. On the basis of the Hamiltonian Ĥ = −2JŜ_Mn(Ŝ_Fe(1) + Ŝ_Fe(2)), the magnetic simulation for the trimeric complexes 2 and 3 gives the magnetic coupling constant 2J_MnFe = −2.68(4) cm⁻¹ for 2 and 2J_MnFe = −2.46(8) cm⁻¹ for 3, respectively. A best-fit to the magnetic susceptibilities of 4 and 5 based on the one-dimensional alternating chain model leads to the magnetic coupling constants 2J₁ = −6.50(2) and 2J₂ = −1.57(1) cm⁻¹ for 4 and 2J₁ = −5.35(2) and 2J₂ = −0.93(1) cm⁻¹ for 5.