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首页> 外文期刊>Chemistry: A European journal >Polytopal Rearrangement of[Ni(acac)_2(py)]:A New Square Pyramid<=>Trigonal Bipyramid Twist Mechanism
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Polytopal Rearrangement of[Ni(acac)_2(py)]:A New Square Pyramid<=>Trigonal Bipyramid Twist Mechanism

机译：[Ni（acac）_2（py）]的多拓扑重排：一个新的方形金字塔<=>三角形双金字塔扭曲机理

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摘要

The interconversion mechanisms between three idealized polyto-pal forms(a square pyramid and two trigonal bipyramids)of[M(bidenta-te)_2(unidentate)]were investigated by an original combination of molecular mechanics(MM)and density functional theory(DFT)approaches.MM was used to model the mechanistic'rearrangement path,and DFT to study selected points along this path.The test case was a five-coordinate[Ni(acac)_2-(py)] species.In the case of [Ni(acac)_2-(py)]it was confirmed(both by MM and by DFT)that the three polytopal forms do indeed represent shallow local minima,of which the square pyramid(SQP)is more stable than the other two.Small energy barriers that separate the three minima prevent spontaneous rearrangement among the polytopal forms in geometry-optimiza-tion simulations.The driving force for MM simulation of the polytopal rearrangements was supplied through the L-M-L angle bending terms.MM results for relative energies and geometries are fully supported by DFT.Finally,the implication of the present results to explain some racemization mechanisms of octahedral complexes(namely,the intramolecular bond rupture of tris(chelate)species,and inter-molecular dissociation of bis(bidentate) species)is briefly discussed.
机译：通过分子力学（MM）和密度泛函理论（DFT）的原始结合研究了[M（bidenta-te）_2（unidentate）]的三种理想化多趾形式（一个方形金字塔和两个三角形双锥体）之间的互变机理方法是使用MM来建模机械装置的重排路径，并使用DFT研究该路径上的选定点。测试用例是五坐标[Ni（acac）_2-（py）]物种。 Ni（acac）_2-（py）]（通过MM和DFT证实）证实了这三种多角体形式确实代表了浅的局部最小值，其中方形金字塔（SQP）比其他两种更稳定。分隔三个极小值的能垒可防止几何优化仿真中多边形形式之间的自发重排。通过LML角弯曲项提供多边形重排的MM模拟的驱动力.MM的相对能量和几何形状的结果完全最后由DFT支持简要讨论了本研究结果，以解释八面体配合物的一些外消旋机制（即，三（螯合物）物种的分子内键断裂和双（双齿）物种的分子间解离）。

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