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首页> 外文期刊>Journal of Molecular Structure. Theochem: Applications of Theoretical Chemistry to Organic, Inorganic and Biological Problems >Preferential interaction of charged alkali metal ions (guest) within a narrow cavity of cyclic crown ethers (neutral host): A quantum chemical investigation
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Preferential interaction of charged alkali metal ions (guest) within a narrow cavity of cyclic crown ethers (neutral host): A quantum chemical investigation

机译：环状冠醚（中性主体）狭窄腔内带电碱金属离子（客体）的优先相互作用：量子化学研究

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摘要

The binding interaction of alkali metal ions (charged guest) within the narrow cavity of crown ethers (neutral host) of different cavity size has been studied using quantum chemical density functional theory. Different conformational structures, binding energies and various thermodynamic parameters of free crown ethers and their metal ion complexes have been determined with the B3LYP functional using a large split valence 6-311++G(d,p) basis set. Geometry optimization was performed using guess structures obtained from semi-empirical PM3 optimized structures without imposing any symmetry restriction. The calculated values of binding enthalpy increase with increase in cavity size, i.e., with increase in donor O atoms and are found to be in good agreement with gas phase experimental results. We have demonstrated the effect of micro-solvation on the binding interaction between the alkali metal ions (Li~+ and Na~+) and the macrocyclic crown ethers by considering micro-solvated metal ions up to six water molecules directly attached to the metal ion. A metal ion exchange reaction involving the replacement of lithium ion in metal ion–crown ether complexes with sodium ion contained within a metal ion–water cluster serves as the basis for modeling binding preferences in solution. An attempt has been made to study the effect of micro-solvation on the binding interaction of metal ions with crown ethers by considering two water molecules attached to metal ion–crown ether complexes. The calculated OAH stretching frequency of H_2O molecule in micro-solvated metal ion–crown complexes is less blue-shifted in comparison to hydrated metal ions. The calculated IR spectra can be compared with an experimental spectrum to determine the presence of micro-solvated metal ion–crown ether complexes in extractant phase.
机译：利用量子化学密度泛函理论研究了碱金属离子（带电客体）在不同腔尺寸的冠醚（中性主体）的窄腔内的键合相互作用。游离冠醚及其金属离子络合物的不同构象结构，结合能和各种热力学参数已通过B3LYP官能团使用大键合价6-311 ++ G（d，p）确定。使用从半经验PM3优化结构获得的猜测结构执行几何优化，而没有施加任何对称性限制。结合焓的计算值随着腔尺寸的增加，即，随着供体O原子的增加而增加，并且发现与气相实验结果非常吻合。通过考虑微溶剂化的金属离子（最多直接与金属离子相连的六个水分子），我们已经证明了微溶剂化对碱金属离子（Li〜+和Na〜+）与大环冠醚之间结合相互作用的影响。金属离子交换反应包括用金属离子-水簇中包含的钠离子替换金属离子-冠醚络合物中的锂离子，作为模拟溶液中结合偏好的基础。尝试通过考虑两个附着在金属离子-冠醚络合物上的水分子来研究微溶剂化对金属离子与冠醚的结合相互作用的影响。与水合金属离子相比，微溶剂化金属离子-冠状配合物中H_2O分子的OAH拉伸频率计算出的蓝移较少。可以将计算出的红外光谱与实验光谱进行比较，以确定萃取剂相中微溶剂化的金属离子-冠状醚络合物的存在。

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