Coordination to metal centers: A tool to fix high energy conformations in organic molecules. Application to 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene and related macrocycles
Coordination to metal centers: A tool to fix high energy conformations in organic molecules. Application to 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene and related macrocycles
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DOI：
10.1039/c1dt11281c
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发表时间：
2011-01-01
影响因子：
4
通讯作者：
Santana, M. D.
中科院分区：
文献类型：
--
作者：
Perez, J.;Carrascosa, R.;Santana, M. D.
利用剑桥结构数据库中的数据，用概率方法测定了配体2，4，4-三甲基-1，5，9-三氮杂环-1-烯(L1)及其9-甲基衍生物(L2)在过渡金属配合物中的固体构象。这些大环化合物作为配体，倾向于采用优先构象(85%的情况)。含有C=N键的环呈扭曲的半椅式构象，由N-sp(3)和N-sp(3)组成的环呈扭曲的包络构象，其余环呈椅式构象。该构象对应于对映体对RN5SN9SP/SN5RN9RP。分子力学计算表明，这是有机分子的高能构象，远离能量极小值。在实验结构中还观察到另外两个对映体对。通过密度泛函理论计算研究了配位对有机配体构象的影响，发现配位对有机配体构象的影响与配位球的几何构型有明显的相关性。
The solid state conformational preferences of ligand 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene (L1) and its 9-methyl derivative (L2) in transition metal complexes have been determined by a probabilistic method using data retrieved from the Cambridge Structural Database. These macrocyclic compounds, as ligands, tend to adopt a preferential conformation (85% of cases). The ring containing the C=N bond adopts a distorted half-chair conformation, the ring defined by both the N-sp(3) shows a distorted envelope conformation, and the remaining ring exhibits a chair conformation. This conformation corresponds to the enantiomer pair RN5SN9SP/SN5RN9RP. Molecular mechanics calculations demonstrate that this is a high energy conformation for the organic molecule, far from the energy minimum. Two other enantiomer pairs are observed in experimental structures. The influence of the coordination on the conformation of the organic ligands has been studied by DFT calculations, and a clear correlation with the geometry of the coordination sphere has been found.