Mn7 and Mn12 Clusters From Use of 2-(Pyridine-2-yl)propan-2-ol: A New Half-Integer Single-Molecule Magnet

The syntheses, crystal structures, and magnetochemical characterization are reported for two new Mn clusters, [Mn7O3(OH)3(O2CBut)7(dmhmp)4] (1) and [Mn12O7(OH)(OMe)2(O2CPh)12(dmhmp)4(H2O)] (2). They were obtained from the use of 2-(pyridine-2-yl)propan-2-ol (dmhmpH), a more bulky version of the 2-(hydroxymethyl)pyridine (hmpH) reagent commonly employed previously in Mn chemistry. The reaction of dmhmpH with MnCl2·4H2O and NaO2CBut in MeCN/MeOH led to the heptanuclear complex 1, whereas the analogous reaction with Mn(O2CPh)2 gave dodecanuclear complex 2. Complexes 1 and 2 are both mixed-valent and are of unprecedented structural types. Complex 1 (MnII, 6MnIII) can be described as the fusion of butterfly-like [Mn4(μ3-O)2] and tetrahedral [Mn4(μ4-O)] units by the sharing of a common Mn atom. Complex 2 (3MnII, 9MnIII) possesses a central [Mn4O6] face-sharing incomplete dicubane, on either side of which is a tetrahedral [Mn4(μ4-O)] unit attached to the oxide ions of the former. Solid-state dc and ac magnetic susceptibility measurements on 1 and 2 establish that they possess unusual S = 7/2 and 13/2 ground states, respectively. The ac susceptibility studies on 2 revealed nonzero frequency-dependent out-of-phase (χM′′) signals at temperatures below 3 K, indicating a single-molecule magnet (SMM). Magnetization versus applied dc field sweeps on single crystals of 2·3CH2Cl2 down to 0.04 K exhibited hysteresis, thus confirming complex 2 to be a new half-integer SMM.

本文报道了两种新型锰簇合物[Mn7O3(OH)3(O2CBut)7(dmhp)4]（1）和[Mn12O7(OH)(OMe)2(O2CPh)12(dmhp)4(H2O)]（2）的合成、晶体结构和磁化学性质。这两种簇合物系通过使用2-(吡啶-2-基)丙-2-醇（dmhpH），该试剂为常用2-(羟甲基)吡啶（hmpH）试剂的更庞大版本，在锰化学中得到了应用。在甲腈/甲醇介质中，dmhpH与MnCl2·4H2O和NaO2CBut的反应产生了七核复杂物1，而与Mn(O2CPh)2的类似反应则生成了十二核复杂物2。复杂物1和2均为多价态，并具有前所未有的结构类型。复杂物1（MnII，6MnIII）可以描述为蝴蝶状[Mn4(μ3-O)2]和四面体[Mn4(μ4-O)]单元通过共享一个共同锰原子而融合。复杂物2（3MnII，9MnIII）具有一个中心的[Mn4O6]面共享不完整的立方烷，在其两侧分别为一个四面体[Mn4(μ4-O)]单元，该单元附着在前者的氧化物离子上。对1和2的固态直流和交流磁化率测量表明，它们分别具有不寻常的S = 7/2和13/2基态。对2的交流磁化率研究发现在低于3K的温度下存在非零频率依赖的出相（χM′′）信号，表明其为单分子磁体（SMM）。在2·3CH2Cl2单晶体中，磁化率与施加的直流场扫描至0.04K时表现出滞后现象，从而证实复杂物2为一种新的半整数值SMM。