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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Tren centered tris-macrocycles as polytopic ligands for Cu(n)and Ni(II)
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Tren centered tris-macrocycles as polytopic ligands for Cu(n)and Ni(II)

机译：Tren中心的tris-macrocycles作为Cu（n）和Ni（II）的多位配体

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摘要

Two novel symmetric polytopic ligands L~1 and L~2 have been synthesized.They are composed of three 1,4,8,11-tetraazacyclotetradecane macrocycles which are connected to a central tren moiety via an ethylene and a trimethylene bridge,respectively.The complexation potential and the speciation diagrams of L~1 and L~2 towards Cu~2+ and Ni~2+ were determined by spectrophotometric and potentiometric titrations.Insight into the geometry of the Cu~2+ complexes is provided by UV-VIS and EPR spectroscopy.The simplified ligands L~3 and L~4 are utilized as references for an aminoethyl-and a tren-substituted tetraaza macrocycle to help assign the EPR spectra of the polytopic ligands L~1 and L~2.At a metal-to-ligand ratio of 3:1,the metal cations are preferentially bound to the tetraaza macrocycles of L~1 and L~2 in a square planar geometry.At high pH values,a nitrogen atom of the tren moiety in L~1 serves as an additional ligand in an axial position leading to a square pyramidal coordination around Cu~2+,whereas in L~2 no such geometry change is observed.At a metal-to-ligand ratio of 4:1,the additional metal cation resides in the central tren moiety of L1 and L2.However,in contrast to the typical trigonal bipyramidal geometry found in the [Cutren]~2+ complex,the fourth Cu2+ has a square pyramidal coordination caused by the interaction with the Cu~2+ cations in the macrocycles(as evidenced by EPR spectra).Since the sequence of metal complexation is such that the first three metal ions always bind to the three macrocycles of L~1 and L~2 and the fourth to the tren unit,it is possible to prepare heteronuclear complexes such as [Cu_3NiL]~8+ or [Ni_3CuL]~8+,which can be unambiguously identified by their spectral properties.
机译：合成了两个新颖的对称多位配体L〜1和L〜2，它们由三个1,4,8,11-四氮杂环十四烷大环组成，它们分别通过乙烯和三亚甲基桥连接到中央tren部分。用分光光度法和电位滴定法测定了L〜1和L〜2对Cu〜2 +和Ni〜2 +的络合势和形态图。 EPR光谱。简化的配体L〜3和L〜4被用作氨乙基和tren取代的四氮杂大环的参考，以帮助分配多位配体L〜1和L〜2的EPR光谱。当配体与配体的比例为3：1时，金属阳离子优先以正方形平面几何形状与L〜1和L〜2的四氮杂大环键合。在高pH值下，L〜1中tren部分的氮原子作为在轴向位置的附加配体，导致围绕周围的方形锥体配位Cu〜2 +，而在L〜2中则没有观察到这种几何变化。在金属与配体的比例为4：1的情况下，额外的金属阳离子驻留在L1和L2的中心tren部分中。在[Cutren]〜2 +配合物中发现的典型三角双锥体几何形状，第四个Cu2 +具有大金字塔中与Cu〜2 +阳离子相互作用的正方形金字塔配位（如EPR光谱所示）。金属络合使得前三个金属离子始终与L〜1和L〜2的三个大环结合，而第四个与tren单元结合，则可以制备诸如[Cu_3NiL]〜8 +或[Ni_3CuL]的杂核络合物]〜8 +，可以通过其光谱特性明确地确定。

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