Department of Chemistry, University of California, Berkeley, California 94720, USA.
J Am Chem Soc. 2011 Dec 28;133(51):20732-4. doi: 10.1021/ja2100142. Epub 2011 Dec 6.
The Ph(4)P(+) salt of the tetrahedral complex Co(SPh)(4), possessing an S = (3)/(2) ground state with an axial zero-field splitting of D = -70 cm(-1), displays single-molecule magnet behavior in the absence of an applied magnetic field. At very low temperatures, ac magnetic susceptibility data show the magnetic relaxation time, τ, to be temperature-independent, while above 2.5 K thermally activated Arrhenius behavior is apparent with U(eff) = 21(1) cm(-1) and τ(0) = 1.0(3) × 10(-7) s. Under an applied field of 1 kOe, τ more closely approximates Arrhenius behavior over the entire temperature range. Upon dilution of the complex within a matrix of the isomorphous compound (Ph(4)P)(2)[Zn(SPh)(4)], ac susceptibility data reveal the molecular nature of the slow magnetic relaxation and indicate that the quantum tunneling pathway observed at low temperatures is likely mediated by intermolecular dipolar interactions.
Ph(4)P(+)盐的四面体配合物 Co(SPh)(4)，具有 S = (3)/(2)基态和轴向零场分裂 D = -70 cm(-1)，在没有外加磁场的情况下表现出单分子磁体行为。在非常低的温度下，交流磁化率数据显示磁弛豫时间 τ 与温度无关，而在 2.5 K 以上则明显表现出热激活 Arrhenius 行为，U(eff) = 21(1) cm(-1)和 τ(0) = 1.0(3) × 10(-7) s。在 1 kOe 的外加磁场下，τ 在整个温度范围内更接近 Arrhenius 行为。在同构化合物 (Ph(4)P)(2)[Zn(SPh)(4)]的基质中稀释配合物后，交流磁化率数据揭示了缓慢磁弛豫的分子性质，并表明低温下观察到的量子隧穿途径可能是通过分子间偶极相互作用介导的。
