Dimitrakopoulou Anastasia, Psycharis Vassilis, Raptopoulou Catherine P, Terzis Aris, Tangoulis Vassilis, Kessissoglou Dimitris P
Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
Inorg Chem. 2008 Sep 1;47(17):7608-14. doi: 10.1021/ic800472c. Epub 2008 Aug 2.
The reaction between Mn(ClO 4) 2 and di-(2-pyridyl)-ketone in the presence of the sodium salt of propanediol as a base in MeOH leads to the formation of a hexanuclear manganese cluster. This cluster has been characterized by the formula [Mn(II) 3Mn(III) 3O(OH)(CH 3pdol) 3(Hpdol) 3(pdol)](ClO 4) 4 ( 1). Molecular conductance measurements of a 10 (-3) M solution of compound 1 in CH 3CN, DMSO, or DMF give Lambda m = 529, 135, or 245 muS/cm, respectively, which suggests a 1:4 cation/anion electrolyte. The crystal structure of hexanuclear manganese cluster 1 consists of two distinct trinuclear units with a pseudocubane-like arrangement. The trinuclear units show two different valence distributions, Mn(II)/Mn(III)/Mn(II) and Mn(III)/Mn(II)/Mn(III). Additional features of interest for the compound include the fact that (a) two of the Mn(III) ions show a Jahn-Teller elongation, whereas the third ion shows a Jahn-Teller compression; (b) one bridge between Mn(III) atoms is an oxo (O (2-)) ion, whereas the bridge between Mn(II) and Mn(III) is a hydroxyl (OH (-)) group; and (c) the di-(2-pyridyl)-ketone ligand that is methanolyzed to methyl-Hpdol and R 2pdol (R = CH 3, H) acts in three different modes: methyl-pdol(-1), Hpdol(-1), and pdol(-2). For magnetic behavior, the general Hamiltonian formalism considers that (a) all of the interactions inside the two "cubanes" between Mn(II) and Mn(III) ions are equal to the J 1 constant, those between Mn(II) ions are equal to the J 2 constant, and those between the Mn(III) ions are equal to the J 3 constant and (b) the interaction between the two cubanes is equal to the J 4 constant. The fitting results are J 1 = J 2 = 0.7 cm (-1), J 3 approximately 0.0, J 4 = -6.2 cm (-1), and g = 2.0 (fixed). According to these results, the ground state is S = 1/2, and the next excited states are S = 3/2 and 5/2 at 0.7 and 1.8 cm (-1), respectively. The EPR spectra prove that the spin ground state at a low temperature is not purely S = 1/2 but is populated with the S = 3/2 state, which is in accordance with the susceptibility and magnetization measurements.
在甲醇中，以丙二醇钠盐作为碱，Mn(ClO₄)₂与二（2 - 吡啶基）酮反应生成一个六核锰簇。该簇的化学式为Mn(II)₃Mn(III)₃O(OH)(CH₃pdol)₃(Hpdol)₃(pdol)₄ (1)。对化合物1在CH₃CN、DMSO或DMF中的10⁻³ M溶液进行分子电导率测量，得到的Λm分别为529、135或245 μS/cm，这表明其为1:4的阳离子/阴离子电解质。六核锰簇1的晶体结构由两个具有类似假立方烷排列的不同三核单元组成。三核单元呈现出两种不同的价态分布，即Mn(II)/Mn(III)/Mn(II)和Mn(III)/Mn(II)/Mn(III)。该化合物其他有趣的特征包括：(a) 两个Mn(III)离子表现出 Jahn - Teller伸长，而第三个离子表现出 Jahn - Teller压缩；(b) Mn(III)原子之间的一个桥是氧（O²⁻）离子，而Mn(II)和Mn(III)之间的桥是羟基（OH⁻）基团；(c) 二（2 - 吡啶基）酮配体被甲醇解为甲基 - Hpdol和R₂pdol（R = CH₃，H），其作用方式有三种：甲基 - pdol⁻¹、Hpdol⁻¹和pdol⁻²。对于磁性行为，一般的哈密顿形式主义认为：(a) 两个“立方烷”内Mn(II)和Mn(III)离子之间的所有相互作用都等于J₁常数，Mn(II)离子之间的相互作用等于J₂常数，Mn(III)离子之间的相互作用等于J₃常数；(b) 两个立方烷之间的相互作用等于J₄常数。拟合结果为J₁ = J₂ = 0.7 cm⁻¹，J₃约为0.0，J₄ = -6.2 cm⁻¹，且g = 2.0（固定）。根据这些结果，基态为S = 1/2，接下来的激发态分别在0.7和1.8 cm⁻¹处为S = 3/2和S = 5/2。电子顺磁共振光谱证明，低温下的自旋基态并非纯粹的S = 1/2，而是含有S = 3/2态，这与磁化率和磁化强度测量结果一致。
