Rational design of cyanide-bridged heterometallic M(I)–Mn(II) (M = Ag, Au) one-dimensional chain complexes: synthesis, crystal structures and magnetic properties

Two mononuclear seven-coordinated macrocycle Mn(II) compounds and four new cyanide-bridged M^I–Mn^II (M = Ag, Au) one-dimensional chain complexes have been synthesized and crystallographically characterized: [Mn(L¹)Cl₂] · H₂O (1), [Mn(L²)Cl₂]·H₂O (2), [Ag(CN)₂Mn(L¹)][Ag(CN)₂] (3), [Ag(CN)₂Mn(L²)][Ag(CN)₂] · 1.5H₂O (4), [Au(CN)₂Mn(L¹)][Au(CN)₂] (5) and [Au(CN)₂Mn(L²)][Au(CN)₂] · 1.5H₂O (6). The structure of the one-dimensional complexes consists of alternating units of [Mn(L)]²⁺ and [M(CN)₂]⁻, generating a cyanide-bridged cationic polymeric chain with [M(CN)₂]⁻ as the counteranion. In all complexes, the coordination geometry of manganese ion is a slightly distorted pentagonal-bipyrimidal with the cyanide nitrogen atoms at the trans positions and N₅ or N₃O₂ coordinating mode in the equatorial plane from ligand L¹ or L². Investigation over magnetic properties of these four one-dimensional complexes reveals the whole very weak antiferromagnetic interaction between neighbouring Mn(II) ions bridged by the long NC–M–CN unit. A best-fit to the magnetic susceptibility of these complexes leads to the magnetic coupling constant of J = −0.065(2), −0.23(3), −0.15(6) and −0.13(5) cm⁻¹ for complex 3, 4, 5, and 6, respectively.