Ground and excited states analysis of alkali metal ethylenediamine and crown ether complexes
Ground and excited states analysis of alkali metal ethylenediamine and crown ether complexes
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DOI：
10.1039/d1cp02552j
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发表时间：
2021-08-19
影响因子：
3.3
通讯作者：
Miliordos, Evangelos
中科院分区：
文献类型：
--
作者：
Ariyarathna, Isuru R.;Miliordos, Evangelos
进行高级电子结构计算，以获得中性锂、钠和钾与两个乙二胺和一个或两个冠醚分子的配合物的优化几何结构和激发能。采用三种不同尺寸的冠（12-crown-4、15-crown-5、18-crown-6）。所有配合物的基态都包含 s 型轨道中的电子。对于单冠醚配合物，该轨道是金属的极化价s轨道，但对于其他系统，该轨道是外围扩散轨道。发现这些物种的低电子态的性质是不同的。具体来说，金属乙二胺配合物遵循先前发现的金属氨配合物的壳模型（1s、1p、1d、2s、1f），但单冠醚配合物和夹心二冠醚配合物都具有不同的壳模型，部分原因在于它们的较低（圆柱）对称性和2s型轨道的稳定性。 Li(15-crown-5)是唯一一个冠醚中间有金属的配合物，接近金属氨配合物的壳模型。我们的研究结果表明，电子化合物（金属冠醚夹层聚集体）和膨胀金属（金属氨聚集体）的电子能带结构应该是不同的，尽管这些系统具有相似的性质（在金属络合物周围带有扩散电子）。
High-level electronic structure calculations are carried out to obtain optimized geometries and excitation energies of neutral lithium, sodium, and potassium complexes with two ethylenediamine and one or two crown ether molecules. Three different sizes of crowns are employed (12-crown-4, 15-crown-5, 18-crown-6). The ground state of all complexes contains an electron in an s-type orbital. For the mono-crown ether complexes, this orbital is the polarized valence s-orbital of the metal, but for the other systems this orbital is a peripheral diffuse orbital. The nature of the low-lying electronic states is found to be different for each of these species. Specifically, the metal ethylenediamine complexes follow the previously discovered shell model of metal ammonia complexes (1s, 1p, 1d, 2s, 1f), but both mono- and sandwich di-crown ether complexes bear a different shell model partially due to their lower (cylindrical) symmetry and the stabilization of the 2s-type orbital. Li(15-crown-5) is the only complex with the metal in the middle of the crown ether and adopts closely the shell model of metal ammonia complexes. Our findings suggest that the electronic band structure of electrides (metal crown ether sandwich aggregates) and expanded metals (metal ammonia aggregates) should be different despite the similar nature of these systems (bearing diffuse electrons around a metal complex).