Constructing single-chain magnets by supramolecular π-π stacking and spin canting: A case study on manganese(III) corroles

摘要

A single-chain magnet (SCM) was constructed from manganese(III) 5,10,15-tris(pentafluorophenyl)corrole complex [Mn ~(III)(tpfc)] through supramolecular π-π stacking without bridging ligands. In the crystal structures, [Mn(tpfc)] molecules crystallized from different solvents, such as methanol, ethyl acetate, and ethanol, exhibit different molecular orientations and intermolecular π-π interaction or weak Mn...O interaction to form a supramolecular one-dimensional motif or dimer. These three complexes show very different magnetic behaviors at low temperature. Methanol solvate 1 shows obvious frequency dependence of out-of-phase alternating-current magnetic susceptibility below 2 K and a magnetization hysteresis loop with a coercive field of 400 Oe at 0.5 K. It is the first example of spin-canted supramolecular single-chain magnet due to weak π-π stacking interaction. By fitting the susceptibility data χ MT (20-300 K) of 1 with the spin Hamiltonian expression H→=-2J∑ ~(n-1) i=1S→ _(Ai)S→ _(Ai+1)+D∑S→ _(iZ) ~2, the intrachain magnetic coupling parameter transmitted by π-π interaction of -0.31 cm -1 and zero field splitting parameter D of -2.59 cm ~(-1) are obtained. Ethyl acetate solvate 2 behaves as an antiferromagnetic chain without ordering or slow magnetic relaxation down to 0.5 K. The magnetic susceptibility data χ _MT (20-300 K) of 2 was fitted by assuming the spin Hamiltonian H→=-2J∑ ~(n-1) _(i=1)S→ _(Ai)S→ _(Ai+1), and the intrachain antiferromagnetic coupling constant of -0.07 cm ~(-1) is much weaker than that of 1. Ethanol solvate 3 with a dimer motif shows field-induced single-molecule magnet like behavior below 2.5 K. The exchange coupling constant J within the dimer propagated by π-π interaction is -0.14 cm -1 by fitting the susceptibility data χ _MT (20-300 K) with the spin Hamiltonian H→=- 2JS→ _AS→ _B+β(S→ _Ag _A+S→ _Bg _B)H. The present studies open a new way to construct SCMs from anisotropic magnetic single-ion units through weak intermolecular interactions in the absence of bridging ligands. Supramolecular magnets: Manganese(III) 5,10,15-tris(pentafluorophenyl)corrole [Mn ~(III)(tpfc)] forms chains or dimers depending on whether it was crystallized from methanol, ethyl acetate, or ethanol. Due to intermolecular π-π interactions, the depicted methanol solvate [Mn(tpfc)(MeOH)] ·H _2O forms a new type of supramolecular spin-canted single-chain magnet without any bridging ligands.