Cyanide-bridged [Fe_8M_6] clusters displaying single-molecule magnetism (M=Ni) and electron-transfer-coupled spin transitions (M=Co)

摘要

Cyanide-bridged metal complexes of [Fe_8M_6(μ-CN) _(14)(CN)_(10) (tp))8(HL)_(10)(CH _3CN)_2][PF_6]_4·nCH _3CN·mH_2O (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 P_2 1. They have tetradecanuclear cores composed of eight low-spin (LS) Fe~(III) and six high-spin (HS) M~(II) 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-Fe~(II))_3(LS-Fe ~(III))_5(HS-Co~(II))_3(LS-Co ~(III))_3] and the [(LS-Fe~(III))_8(HS- Co~(II))_6] states.