A trinuclear copper(II) cryptate and its μ3-CO3 cascade complex: thermodynamics, structural and magnetic properties.
A trinuclear copper(II) cryptate and its μ3-CO3 cascade complex: thermodynamics, structural and magnetic properties.
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DOI：
10.1002/chem.201101372
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发表时间：
2011-09
期刊：
影响因子：
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通讯作者：
P. Mateus;R. Delgado;F. Lloret;J. Cano;P. Brandão;V. Félix
中科院分区：
文献类型：
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作者：
P. Mateus;R. Delgado;F. Lloret;J. Cano;P. Brandão;V. Félix
2，4，6-三乙苯封端的吡啶基间隔基(PYR)六胺大环可与3个铜(II)离子配位。在298.2 K的甲醇/H(2)O(50：50 v/v)和0.10moldm(-3)的KNO(-3)溶液中进行的电位研究表明，在pH为5.0的溶液中，三核物种占主导地位，羟基络合物是主要物种，在极低的pH值下开始形成。三核配合物的单晶X射线测定表明，这三个铜中心具有正方形的平面几何结构，排列成几乎等边的三角形，三个金属中心之间有碳酸盐桥联。碳酸盐的存在是大气CO(2)固定的结果。本研究是第一个μ(3)-CO(3)桥联三核铜(II)配合物，位于一个大双环空腔的内部。[Cu(3)(PYR)(μ(3)-CO(3))]·(ClO(4))(4)[J=3.8 cm(-1)，基于哈密顿H=-J(S(1)S(2)+S(2)S(3)+S(1)S(3))]产生了一个自旋四重态，S=3/2，基态。对三核配合物的实验几何构型的密度泛函计算表明，磁耦合的铁磁性可以归因于碳桥的同步-反构象，并提出了基于不同构象(同步-反构象、同步-反构象和反构象)的磁-结构关联。观察到的有趣的性质，即配位水分子的pK(A)降低到不寻常的值，以及铜中心之间碳酸盐阴离子的良好匹配，来自于PYR的特殊结构。
The 2,4,6-triethylbenzene-capped hexaamine macrobicycle with pyridyl spacers (pyr) was able to coordinate three copper(II) ions within its cavity. Potentiometric studies performed at 298.2 K in MeOH/H(2)O (50:50 v/v) and at ionic strength 0.10 mol dm(-3) in KNO(3) revealed that trinuclear species predominate in solution from pH 5.0, the hydroxo complexes being the main species, which start forming at unusual very low pH values. The single-crystal X-ray determination of the trinuclear complex showed that the three copper centres have square-planar geometry, arranged in an almost equilateral triangle, and have carbonate bridging the three metal centres. The presence of carbonate resulted from fixation of atmospheric CO(2). The present study represents the first μ(3)-CO(3)-bridged trinuclear copper(II) complex located in the interior of a macrobicyclic cavity. The magnetic data of [Cu(3)(pyr)(μ(3)-CO(3))]·(ClO(4))(4) showed ferromagnetic intramolecular interactions [J=3.80 cm(-1), based on the Hamiltonian H=-J(S(1)S(2)+S(2)S(3)+S(1)S(3))] yielding a spin quartet, S=3/2, ground state. Density functional calculations on the experimental geometry of the trinuclear complex showed that the ferromagnetic nature of the magnetic coupling can be attributed to the syn-anti conformation of the carbonato bridge, and a magneto-structural correlation, based on the different conformations (syn-anti, syn-syn and anti-anti), is presented. The interesting properties observed, namely the lowering of the pK(a) of coordinated water molecules to unusual values and the good fit of the carbonate anion between the copper centres, derive from the special architecture of pyr.