A study of the Group 1 metal tetra-aza macrocyclic complexes [M(Me4cyclen)(L)]+ using electronic structure calculations,Dalton Transactions

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A study of the Group 1 metal tetra-aza macrocyclic complexes [M(Me4cyclen)(L)]+ using electronic structure calculations
Dalton Transactions ( IF 3.5 ) Pub Date : 2017-10-16 00:00:00 , DOI: 10.1039/c7dt03002a
Hanusha Bhakhoa _{1,

2,

3,

4,

5} , Lydia Rhyman _{1,

2,

3,

4,

5} , Edmond P. Lee _{6,

7,

8,

9,

10} , Daniel K. W. Mok _{10,

11,

12,

13} , Ponnadurai Ramasami _{1,

2,

3,

4,

5} , John M. Dyke _{6,

7,

8,

9}

Affiliation

Metal-cyclen complexes have a number of important applications. However, the coordination chemistry between metal ions and cyclen-based macrocycles is much less well studied compared to their metal ion-crown ether analogues. This work, which makes a contribution to address this imbalance by studying complex ions of the type [M(Me₄cyclen)(L)]⁺, was initiated by results of an experimental study which prepared some Group 1 metal cyclen complexes, namely [Li(Me₄cyclen)(H₂O)][BAr^F] and [Na(Me₄cyclen)(THF)][BAr^F] and obtained their X-ray crystal structures [J. M. Dyke, W. Levason, M. E. Light, D. Pugh, G. Reid, H. Bhakhoa, P. Ramasami, and L. Rhyman, Dalton Trans., 2015, 44, 13853]. The lowest [M(Me₄cyclen)(L)]⁺ minimum energy structures (M = Li, Na, K, and L = H₂O, THF, DEE, MeOH, DCM) are studied using density functional theory (DFT) calculations. The geometry of each [M(Me₄cyclen)(L)]⁺ structure and, in particular, the conformation of L are found to be mainly governed by steric hindrance which decreases as the size of the ionic radius increases from Li⁺ → Na⁺ → K⁺. Good agreement of computed geometrical parameters of [Li(Me₄cyclen)(H₂O)]⁺ and [Na(Me₄cyclen)(THF)]⁺ with the corresponding geometrical parameters derived from the crystal structures [Li(Me₄cyclen)(H₂O)]⁺[BAr^F]⁻ and [Na(Me₄cyclen)(THF)]⁺[BAr^F]⁻ is obtained. Bonding analysis indicates that the stability of the [M(Me₄cyclen)(L)]⁺ structures originates mainly from ionic interaction between the Me₄cyclen/L ligands and the M⁺ centres. The experimental observation that [M(Me₄cyclen)(L)]⁺[BAr^F]⁻ complexes could be prepared in crystalline form for M⁺ = Li⁺ and Na⁺, but that experiments aimed at synthesising the corresponding K⁺, Rb⁺, and Cs⁺ complexes failed resulting in formation of [Me₄cyclenH][BAr^F] is investigated using DFT and explicitly correlated calculations, and explained by considering production of [Me₄cyclenH]⁺ by a hydrolysis reaction, involving traces of water, which competes with [M(Me₄cyclen)(L)]⁺ formation. [Me₄cyclenH]⁺ formation dominates for M⁺ = K⁺, Rb⁺, and Cs⁺ whereas formation of [M(Me₄cyclen)(L)]⁺ is energetically favoured for M⁺ = Li⁺ and Na⁺. The results indicate that the number and type of ligands, play a key role in stabilising the [M(Me₄cyclen)]⁺ complexes and it is hoped that this work will encourage experimentalists to prepare and characterise other [M(Me₄cyclen)(L)]⁺ complexes.

中文翻译：

使用电子结构计算研究第1组金属四氮杂大环配合物[M（Me ₄ cyclen）（L）] ⁺

金属环复合物具有许多重要的应用。但是，与其金属离子冠醚类似物相比，金属离子与基于Cyclenn的大环之间的配位化学研究得很少。这项工作是通过研究[M（Me ₄ cyclen）（L）] ⁺类型的复杂离子为解决这种不平衡做出贡献的，这项工作是通过一项实验研究的结果开始的，该实验制备了一些第1组金属周期素络合物，即[ Li（Me ₄ cyclen）（H ₂ O）] [BAr ^F ]和[Na（Me ₄ cyclen）（THF）] [BAr ^F ]并获得其X射线晶体结构[JM Dyke，W.Levason，ME Light ，D。Pugh，G。Reid，H。Bhakhoa，P。Ramasami和L. Rhyman，道尔顿跨。，2015，44，13853]。使用密度泛函理论（DFT）研究了最低的[M（Me ₄循环数）（L）] ⁺最小的能量结构（M = Li，Na，K和L = H ₂ O，THF，DEE，MeOH，DCM）计算。发现每个[M（Me ₄ cyclen）（L）] ⁺结构的几何形状，尤其是L的构象主要受空间位阻支配，随着离子半径的大小从Li ⁺ →Na增大，空间位阻减小⁺ →K ⁺。[Li（Me ₄ cyclen）（H ₂ O）] ⁺和[Na（Me₄环n）（THF）]⁺，并从晶体结构[Li（Me₄环）（H₂ O）]⁺ [BAr^F ]^-和[Na（Me₄环）（THF）]⁺导出相应的几何参数⁺获得[BAr^F ]^-。键合分析表明，[M（Me₄周期蛋白）（L）]⁺结构的稳定性主要源自Me₄周期蛋白/ L配体与M⁺中心之间的离子相互作用。[M（Me₄ cyclen）（L）]⁺ [BAr对于M⁺ = Li⁺和Na⁺，可以以晶体形式制备^F ]^-络合物，但旨在合成相应的K⁺，Rb⁺和Cs⁺络合物的实验失败，导致形成[Me₄ cyclenH] [BAr使用DFT和显式相关的计算研究^F ]，并通过考虑通过水解反应产生[Me₄ cyclenH]⁺的方法进行解释，其中涉及痕量水，该水与[M（Me₄ cyclen）（L）]⁺形成竞争。[Me₄ cyclenH]⁺形成占优势对于M ⁺ = K ⁺，RB ⁺，和Cs ⁺而形成[M（ME的₄环烯）（L）] ⁺是能量上有利对于M ⁺ =栗⁺和Na ⁺。结果表明，配体的数量和类型在稳定[M（Me ₄ cyclen）] ⁺络合物中起着关键作用，希望这项工作能够鼓励实验人员制备和表征其他[M（Me ₄ cyclen）] （L）] ⁺配合物。

更新日期：2017-11-15

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