Judicious design of ligand scaffolds to highly anisotropic lanthanide ions led to substantial advances in molecular spintronics and single-molecule magnetism. Erbium-based single-molecule magnets (SMMs) are rare, which is attributed to the prolate-shaped Er^III ion requiring an equatorial ligand field for enhancing its single-ion magnetic anisotropy. Here, we present an electron-rich mononuclear Er SMM, [K(crypt-222)][Er(dbCOT)₂], 1 (where dbCOT = dibenzocyclooctatetraene), that was obtained from a salt metathesis reaction of ErCl₃ and K₂dbCOT. The dipotassium salt, K₂dbCOT, was generated through a two-electron reduction of the bare dbCOT⁰ ligand employing potassium graphite and was crystallized from DME to give the new solvated complex, [K(DME)]₂[dbCOT]_n, 2. 1 was analyzed through crystallography, electrochemistry, spectroscopy, magnetometry, and CASSCF calculations. The structure of 1 consists of an anionic metallocene complex featuring a linear (180.0°) geometry with an Er^III ion sandwiched between dianionic dbCOT ligands and an outer-sphere K⁺ ion encapsulated in 2.2.2-cryptand. Two pronounced redox events at negative potentials allude to the formation of a trianionic erbocene complex, [Er(dbCOT)₂]^3–, on the electrochemical time scale. 1 shows slow magnetic relaxation with an effective spin-reversal barrier of U_eff = 114(2) cm^–1, which is close in magnitude to the calculated energies of the first and second excited states of 96.9 and 109.13 cm^–1, respectively. 1 exhibits waist-constricted hysteresis loops below 4 K and constitutes the first example of an erbocene-SMM bearing fused aromatic rings to the central COT ligand. Notably, 1 comprises the largest COT scaffold implemented in erbocene SMMs, yielding the most electron-rich homoleptic erbium metallocene SMM.

中文翻译：

---

具有二苯并环辛四烯配体的线性富电子铒单分子磁体


针对高度各向异性的镧系离子的配体支架的明智设计导致了分子自旋电子学和单分子磁性的重大进展。铒基单分子磁体（SMM）很少见，这是由于长形状的Er ^III 离子需要赤道配体场来增强其单离子磁各向异性。在这里，我们提出了一种富电子单核 Er SMM，[K(crypt-222)][Er(dbCOT) ₂ ], 1（其中 dbCOT = 二苯并环辛四烯），它是通过盐复分解反应获得的ErCl ₃ 和 K ₂ dbCOT。二钾盐 K ₂ dbCOT 是通过使用钾石墨对裸露 dbCOT ⁰ 配体进行双电子还原而生成的，并从 DME 中结晶得到新的溶剂化络合物，[ K(DME)] ₂ [dbCOT] _n , 2. 1 通过晶体学、电化学、光谱学、磁力测定和 CASSCF 计算进行分析。 1 的结构由具有线性 (180.0°) 几何形状的阴离子茂金属络合物组成，其中 Er ^III 离子夹在双阴离子 dbCOT 配体之间，外层 K ⁺ 离子封装在2.2.2-密码子。负电势下的两个明显的氧化还原事件暗示在电化学时间尺度上形成了三阴离子二茂络合物 [Er(dbCOT) ₂ ] ^3– 。图 1 显示了慢磁弛豫，有效自旋反转势垒为 U _eff = 114(2) cm ^–1 ，其大小与第一和第二激发的计算能量接近状态分别为 96.9 和 109.13 cm ^–1 。图1在4K以下表现出腰部收缩的磁滞回线，并构成了带有稠合芳环与中心COT配体的erbocene-SMM的第一个例子。 值得注意的是，1 包括二茂 SMM 中实现的最大的 COT 支架，产生最富电子的均配铒茂金属 SMM。