Studies on the Magnetic Interactions in Self-Assembled Cage Complexes

Abstract

Our research focuses on electron transfer coupled spin transition (ETCST) behavior, which has been observed in cobalt-iron cyanide-bridged complexes. We have already reported that the self-assembled cyanide-bridged decanuclear nickel-iron cage complex (Et₄N)[Ni(L^R)₂]₆[Fe(CN)₆]₄(PF₆) ( L^R = N-(2-pyridylmethylene)- (R)-1-phenylethylamine) has a spin ground state of S_T = 8. In this work, the magnetic properties of the self-assembled decanuclear cobalt-iron cage analogues (Et₄N)₂[Co(L^R)₂]₆[Fe(CN)₆]₄(X) ( X = BF₄^-(1), [Ni(mnt)₂]^-(2) (mnt = dimercaptomaleonitrile)), which were expected to show ETCST behavior, were investigated. The chi_mT value of 1 rapidly rose around 250 K as temperature increased, suggesting the occurrence of the ETCST phenomenon. On the other hand, 2 had a high-spin ground state at low temperature, resulting from ferromagnetic interactions between the cobalt-iron ions. This suggests that the magnetic properties of the cluster can be controlled through the choice of counter anion.