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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Kinetics and mechanism of the stepwise complex formation of Cu(II)with tren-centered tris-macrocycles
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Kinetics and mechanism of the stepwise complex formation of Cu(II)with tren-centered tris-macrocycles

机译：居中性的tris-大环化合物逐步形成Cu（II）的动力学和机理

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摘要

The stepwise complexation kinetics of Cu~(2+)with three tetratopic ligands L~1,L~2 and L~3,tren-centred macrocycles with different bridges connecting the 14-membered macrocycles with the tren unit,have been measured by stopped-flow photodiode array techniques at 25 deg C,/ = 0.5 M(KN_O3),and pH = 4.96.The reaction between the first Cu~(2+)and the ligand consists of several steps.In a rapid reaction Cu~(2+)first binds to the flexible and more reactive tren-unit.In this intermediate a translocation from the tren unit to the macrocyclic ring,which forms the thermodynamic more stable complex,takes place.This species can react further with a second Cu~(2+)to give a heterotopic dinuclear species with one Cu~(2+)bound by the tren-unit and the other coordinated by the macrocycle.A further translocation occurs to give the homoditopic species with two Cu~(2+)in the macrocycles.Finally a slow rearrangement of the dinuclear complex gives the final species.The rates of the translocation are dependent on the length and rigidity of the bridge,whereas the complexation rates with the tren unit are little affected by it.VIS spectra of the species obtained by fitting the kinetic results,EPR-spectra taken during the reaction,and ES mass spectra of the products confirm the proposed mechanism.The addition of a second,third and fourth equivalent of Cu~(2+)proceeds in an analogous way,but is complicated by the fact that we start and end with a mixture of species.These steps were evaluated in a qualitative way only.
机译：Cu〜（2+）与三个四位配体L〜1，L〜2和L〜3的居中分步络合动力学，带有以14位大环与tren单元连接的不同桥的居中大环通过停止测量流光电二极管阵列技术在25°C / = 0.5 M（KN_O3），pH = 4.96的条件下进行。第一个Cu〜（2+）与配体之间的反应包括几个步骤。 +）首先与柔性且反应性更高的tren单元结合。在该中间体中，发生了从tren单元到大环的易位，形成了热力学更稳定的复合物，该物种可以与第二个Cu〜（进一步反应）。 2+）产生异位双核物种，其中一个Cu〜（2+）与tren-unit结合，另一个由大环协调。最终，双核复合物的缓慢重排产生了最终的物种。易位的速率取决于取决于桥的长度和刚度，而与tren单元的络合速率几乎不受其影响。通过拟合动力学结果获得的物质的VIS光谱，反应过程中获得的EPR光谱和Es质谱产品证实了拟议的机理。以类似的方式添加了第二，第三和第四当量的Cu〜（2+），但是由于我们以物种的混合物开始和结束而变得复杂。对这些步骤进行了评估仅以定性的方式。

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