Concerted Ligand Exchange and the Roles of Counter Anions in the Reversible Structural Switching of Crystalline Peptide Metallo-Macrocycles
Concerted Ligand Exchange and the Roles of Counter Anions in the Reversible Structural Switching of Crystalline Peptide Metallo-Macrocycles
复制标题
协同配体交换和抗衡阴离子在结晶肽金属大环可逆结构转换中的作用
DOI：
10.1021/ic500478p
复制
发表时间：
2014
影响因子：
4.6
通讯作者：
M. Shionoya
中科院分区：
文献类型：
--
作者：
R. Miyake;M. Shionoya
为了理解晶体材料中可逆的结构转换，我们研究了由人工β-二肽组成的四核Ni Ⅱ大环的可逆晶体-晶体转换机制。本文通过对NO_3和BF_4两种准同构晶体的结构分析和热力学测量，讨论了晶体中水含量和温度的变化对配体交换反应的影响。NO3盐的结构转变的观察表明，假晶相转变发生通过协调的配体交换反应在四个Ni III中心的大环与氢键切换。这种配体交换的机制是由红外光谱支持。热力学测量表明，由于吸水和结构变化的焓变的良好的补偿关系是可逆的结构转变的关键。在与伪同构晶体的比较的基础上，很明显，晶体的堆积结构和抗衡阴离子的类型是促进具有单晶的可逆配体交换的重要因素。
To understand reversible structural switching in crystalline materials, we studied the mechanism of reversible crystal-to-crystal transformation of a tetranuclear NiIImacrocycle consisting of artificial β-dipeptides. On the basis of detailed structural analyses and thermodynamic measurements made in a comparison of pseudo-isostructural crystals (NO3and BF4salts), we herein discuss how ligand-exchange reactions take place in the crystal due to changes in water content and temperature. Observations of the structural transformation of NO3salt indicated that a pseudo crystalline phase transformation takes place through concerted ligand-exchange reactions at the four NiIIcenters of the macrocycle with hydrogen bond switching. A mechanism for this ligand exchange was supported by IR spectroscopy. Thermodynamic measurements suggested that the favorable compensation relationship of the enthalpy changes due to water uptake and structural changes are keys to the reversible structural transformation. On the basis of a comparison with the pseudo-isostructural crystals, it is apparent that the crystal packing structure and the types of counter anions are important factors for facilitating reversible ligand exchange with single crystallinity.