Reinoso Santiago, Vitoria Pablo, San Felices Leire, Montero Ainara, Lezama Luis, Gutiérrez-Zorrilla Juan M
Departamento de Química InorgAnica, Facultad de Ciencia y Tecnología, Universidad del País Vasco, P.O. Box 644, E-48080 Bilbao, Spain.
Inorg Chem. 2007 Feb 19;46(4):1237-49. doi: 10.1021/ic061671m. Epub 2007 Jan 23.
The use of tetrahydroxy-p-benzoquinone as a slow source of dihydroxymalonato and oxalato ligands led to the isolation under open-air mild reaction conditions of five different compounds, two of them prepared for the first time: [Cu(bpy)(dhmal)]2 (1) and [{SiW12O40}{Cu2(bpy)2(H2O)(ox)}2].16H2O (5) (bpy, 2,2'-bipyridine; dhmal, dihydroxymalonate; ox, oxalate). A possible mechanism for the oxidation of the benzoquinone to give the croconate dianion, which undergoes further ring-opening oxidation to decompose into dihydroxymalonate and oxalate, is proposed. All compounds have been characterized by elemental analysis, thermogravimetry, infrared spectroscopy, and powder X-ray diffraction. Single-crystal X-ray diffraction, electron paramagnetic resonance, and magnetic susceptibility measurements have been performed for compounds 1 and 5. A complete band assignment of the experimental FT-IR spectra is given through comparison with the ones calculated using density functional theory (DFT). The neutral dimer 1 constitutes the first structurally characterized example of a transition metal-dhmal complex, and it contains two copper atoms bridged by two dihydroxymalonato ligands acting in a mu2-kappa3O,O',O":kappa1O coordination fashion, so that an equatorial-axial Cu2(mu2-O)2 rhomboid core is formed. On the other hand, the inorganic-metalorganic hybrid compound 5 shows a two-dimensional arrangement of Keggin polyanions linked by one of the Cu atoms of the oxalate cationic dimers to give layers parallel to the (10) plane, the remaining ox-Cu-bpy fragments acting as interlamellar separators. In both cases, magnetic and EPR results are discussed with respect to the crystal structure of the compounds and, for compound 1, also with respect to DFT calculations of the exchange coupling constant.
使用四羟基对苯醌作为二羟基丙二酸根和草酸根配体的缓慢来源，在露天温和反应条件下分离出了五种不同的化合物，其中两种是首次制备的：[Cu(bpy)(dhmal)]2 (1) 和 [{SiW12O40}{Cu2(bpy)2(H2O)(ox)}2].16H2O (5)（bpy 为 2,2'-联吡啶；dhmal 为二羟基丙二酸根；ox 为草酸根）。提出了一种苯醌氧化生成藏红花酸二价阴离子的可能机制，该阴离子会进一步发生开环氧化分解为二羟基丙二酸根和草酸根。所有化合物均通过元素分析、热重分析、红外光谱和粉末 X 射线衍射进行了表征。对化合物 1 和 5 进行了单晶 X 射线衍射、电子顺磁共振和磁化率测量。通过与使用密度泛函理论 (DFT) 计算的光谱进行比较，给出了实验 FT-IR 光谱的完整谱带归属。中性二聚体 1 是过渡金属 - dhmal配合物的第一个结构表征实例，它包含两个铜原子，由两个以μ2-κ3O,O',O":κ1O配位方式作用的二羟基丙二酸根配体桥联，从而形成一个赤道 - 轴向的Cu2(μ2-O)2菱形核心。另一方面，无机 - 金属有机杂化化合物5显示出Keggin聚阴离子的二维排列方式，通过草酸根阳离子二聚体的一个铜原子相连，形成平行于(10)平面的层，其余的ox-Cu-bpy片段充当层间分隔物。在这两种情况下，都根据化合物的晶体结构讨论了磁性和EPR结果，对于化合物1，还根据交换耦合常数的DFT计算进行了讨论。
