Cyanide-Bridged [Fe₈M₆] Clusters Displaying Single-Molecule Magnetism (M=Ni) and Electron-Transfer-Coupled Spin Transitions (M=Co)

摘要

Cyanide-bridged metal complexes of [Fe₈M₆(μ-CN)₁₄(CN)₁₀ (tp)₈(HL)₁₀(CH₃CN)₂][PF₆]₄n CH₃CNm H₂O (HL=3-(2-pyridyl)-5-[4-(diphenylamino)phenyl]-1H-pyrazole), tp−=hydrotris(pyrazolylborate), 1: M=Ni with n=11 and m=7, and 2: M=Co with n=14 and m=5) were prepared. Complexes 1 and 2 are isomorphous, and crystallized in the monoclinic space group P2₁. They have tetradecanuclear cores composed of eight low-spin (LS) FeIII and six high-spin (HS) MII ions (M=Ni and Co), all of which are bridged by cyanide ions, to form a crown-like core structure. Magnetic susceptibility measurements revealed that intramolecular ferro- and antiferromagnetic interactions are operative in 1 and in a fresh sample of 2, respectively. Ac magnetic susceptibility measurements of 1 showed frequency-dependent in- and out-of-phase signals, characteristic of single-molecule magnetism (SMM), while desolvated samples of 2 showed thermal- and photoinduced intramolecular electron-transfer-coupled spin transition (ETCST) between the [(LS-FeII)₃(LS-FeIII)₅(HS-CoII)₃(LS-CoIII)₃] and the [(LS-FeIII)₈(HS-CoII)₆] states.