Sajjad Saira, Ali Akhtar, Mahmood Tariq, Ayub Khurshid
Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad, KPK, 22060, Pakistan.
Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad, KPK, 22060, Pakistan.
J Mol Graph Model. 2020 Nov;100:107668. doi: 10.1016/j.jmgm.2020.107668. Epub 2020 Jul 8.
Alkaline earthide is a well-known class of the excess electron compounds with potential applications as NLO materials. In this study, all-cis-1,2,3,4,5,6-hexafluor-ocyclohexane CHF (1), a high polarized complexant having the largest dipole moment (6.2D) among all the known aliphatic hydrocarbons, is selected as a suitable molecule for designing a new series of excess electron molecules, alkaline-earthides. Geometric, thermodynamic and electronic properties of A-1-AE (A = Li, Na, K and AE = Be, Mg, Ca) are studied at M06-2X/6-31+G(d,p) level of theory. More specifically, alkaline-earthide nature is confirmed by distribution of densities in HOMOs, VIE values and NBO analysis. The alkaline earthide possess moderate complexation energies (-6.56 to -14.19 kcal/mol), which demonstrate their thermodynamic stability. These alkaline earthides possess very small excitation energies (0.54-1.64 eV) and very large first hyperpolarizabilities (up to 4.14 × 10 au). The higher hyperpolarizabilities values are attributed to the presence of excess electrons on alkaline earth metals which is confirmed through the partial density of states (PDOS) analysis. The hyperpolarizabilities are rationalized through two level model approach. Large hyperpolarizability values illustrate that the alkaline-earthides are a very promising entry into excess electron compounds.
碱土化物是一类著名的具有潜在应用价值的NLO材料的过电子化合物。在本研究中，全顺式-1,2,3,4,5,6-六氟环己烷CHF（1），一种在所有已知脂肪烃中具有最大偶极矩（6.2D）的高极化络合剂，被选为设计一系列新的过电子分子——碱土化物的合适分子。在M06 - 2X/6 - 31 + G(d,p)理论水平上研究了A - 1 - AE（A = Li、Na、K，AE = Be、Mg、Ca）的几何、热力学和电子性质。更具体地说，通过HOMO中的密度分布、VIE值和NBO分析证实了碱土化物的性质。碱土化物具有适度的络合能（-6.56至-14.19 kcal/mol），这表明了它们的热力学稳定性。这些碱土化物具有非常小的激发能（0.54 - 1.64 eV）和非常大的第一超极化率（高达4.14×10 au）。较高的超极化率值归因于碱土金属上存在过电子，这通过态密度（PDOS）分析得到证实。通过双能级模型方法对超极化率进行了合理化解释。大的超极化率值表明碱土化物是过电子化合物中非常有前景的一类。
