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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >First principles studies toward the design of silylene superbases: A density functional theory study
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First principles studies toward the design of silylene superbases: A density functional theory study

机译：甲硅烷基超碱设计的首要原理研究：密度泛函理论研究

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In this paper we have reported for the first time some designed silylene superbases using DFT calculations. These divalent Si(II) compounds can act as powerful neutral organic superbases in the gas phase and in the solvent phase. The DFT calculations performed with the B3LYP/6-311+G**//B3LYP/6-31+G* level of theory showed that one of the designed silylene derivatives:Si(N?-PY_3)_2 [Y =-N?-C(NMe_2)_2] (8) can fall in the range of hyperbase with gas phase proton affinity ～310 kcal/mol. In THF the calculated proton affinity of 8 was found to be 327.5 kcal/mol. The proton affinities computed at the B3LYP/6-311+G*//B3LYP/6-31+G* level for some simple silylenes have been found to be good agreement with the corresponding experimentally measured values. Phosphazene groups attached to the divalent silicon center of silylenes enhanced the basicity of the Si center significantly and further acted as a second protonation site. The calculated second proton affinity of the silylene derivative, 8 in THF was found to be 285.5 kcal/mol. We have shown that the dimerization and cyclization of such silyene superbases were less likely and the monomeric forms would be more stable than their corresponding dimers. The calculated proton affinities also showed a good correlation with the HOMO-LUMO energy gap and energy difference between the singlet and triplet states (ΔE_(S-T)) of the silylene systems. The isodesmic reactions have been employed to examine the stability of the silylene molecules by calculating the silylene stabilization energy (SiSE). The reactivity of silylene molecules has been presented in terms of the nucleophilicity, electronegativity, and hardness of such systems. The Lewis basic properties of these silylene systems have also been explored.
机译：在本文中，我们首次报告了使用DFT计算设计的一些甲硅烷基超碱。这些二价Si（II）化合物可在气相和溶剂相中充当强大的中性有机超碱。用B3LYP / 6-311 + G ** // B3LYP / 6-31 + G *理论水平进行的DFT计算表明，设计的甲硅烷基衍生物之一：Si（N？-PY_3）_2 [Y = -N α-C（NMe_2）_2]（8）可以在高碱范围内，气相质子亲和力约为310 kcal / mol。在THF中，计算出的8的质子亲和力为327.5kcal / mol。发现一些简单的甲硅烷基在B3LYP / 6-311 + G * // B3LYP / 6-31 + G *浓度下计算出的质子亲合力与相应的实验测量值良好吻合。与亚甲硅烷基的二价硅中心相连的磷腈基团大大提高了Si中心的碱度，并进一步充当了第二个质子化位点。发现亚甲硅烷基衍生物在THF中的第二质子亲和力的计算值为285.5kcal / mol。我们已经表明，这种甲硅烷基超碱的二聚和环化的可能性较小，并且单体形式比其相应的二聚体更稳定。计算出的质子亲合力也与HOMO-LUMO能隙以及亚甲硅烷基系统的单重态和三重态之间的能量差（ΔE_（S-T））具有良好的相关性。等渗反应已用于通过计算甲硅烷基稳定能（SiSE）来检查甲硅烷基分子的稳定性。已经根据此类体系的亲核性，电负性和硬度提出了亚甲硅烷基分子的反应性。还研究了这些亚甲硅烷基体系的路易斯基本性质。

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