Synthesis, crystal structures and magnetic properties of cyanide-bridged macrocyclic complexes

Three cyanide-bridged dodecanuclear macrocyclic wheel-like complexes [Cr(bpmb)(CN)2]6[Mn(5-Brsalpn)]6-12H2O (1), [Co(bpmb)(CN)2]6[Mn(5-Brsalpn)]6-12H2O (2) and [Co(bpmb)(CN)2]6[Mn(5-Clsalpn)]6-24H2O-8CH3CN (3) [bpmb2- = 1,2-bis(pyridine-2-carboxamido)-4-methylbenzenate dianion; 5-Brsalpn2-= N,N’-propylenebis(5-bromosalicylideneaminato) dianion; 5-Clsalpn2-= N,N’-propylenebis(5-chlorosalicylideneaminato) dianion] have been synthesized and their crystal structures and magnetic properties have been investigated. The three compounds are structurally isomorphous and consist of alternating Mn( Ⅲ )-Schiff base cations and [M(bpmb)(CN)2]- anions, generating cyanide-bridged nanosized dodecanuclear macrocyclic structures with an approximate diameter of 2 nm. The study of the magnetic properties of complex 1 reveals an antiferromagnetic interaction between the Cr(Ⅲ) and Mn(Ⅲ) ions through the cyanide bridges. A best-fit to the magnetic susceptibility of the complex leads to a magnetic coupling constant of JCrMn = -2.65(6) cm-1 on the basis of a one-dimensional alternating chain model with the Hamiltonian H =-JCrMn∑N to 1=0 Si·Si+1.