Capturing a Synergistic Effect of a Conical Push and an Inward Pull in Fluoro Derivatives of Li@B10H14 Basket: Toward a Higher Vertical Ionization Potential and Nonlinear Optical

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• 作者：Shabbir Muhammad ; Hongliang Xu ; Zhongmin Su
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：February 10, 2011
• 年：2011
• 卷：115
• 期：5
• 页码：923-931
• 全文大小：1092K
• 年卷期：v.115,no.5(February 10, 2011)
• ISSN：1520-5215

文摘

We present the design of fluoro derivatives of B₁₀H₁₄ and Li@B₁₀H₁₄ baskets. A synergistic effect of conical push and inward pull (reported independently in previous lithium nonlinear optical (NLO) complexes) has been explored in these derivatives to achieve a robustly large NLO response and a higher vertical ionization potential. Li@1,3,6,9-F₄B₁₀H₁₀, Li@6,9-F₂B₁₀H₁₂, and Li@2,4,6,9-F₄B₁₀H₁₀ exhibit first hyperpolarizability (尾₀) values as large as 181鈥?24, 133鈥?99, and 32鈥?14 au; their vertical ionization potentials are 6.45, 6.30, and 6.78 eV, respectively. These values are significantly higher than those previously reported in Li-doped fluorocarbon chains at the same MP2/6-31+G* level of theory (Xu, H. L.; Li, Z. R.; Wu, D.; Wang, B. Q.; Li, Y.; Gu, F. L.; Aoki, Y. J. Am. Chem. Soc. 2007, 129, 2967). They also exceed those from our earlier designed Li@B₁₀H₁₄ basket (Muhammad, S.; Xu, H. L.; Liao, Y.; Kan, Y. H.; Su, Z. M. J. Am. Chem. Soc. 2009, 131, 2967). In addition, new quantum chemical calculations of enthalpies of reaction (螖_rH掳) at 298 K for B₁₀H₁₄ and its lithium/fluoro derivatives highlight the changes in their thermodynamical aspects. The calculated enthalpies of lithiation reactions are 鈭?0.04, 鈭?1.29, and 鈭?3.18 kcal/mol for B₁₀H₁₄, 6,9-F₂B₁₀H₁₂, and 2,4-F₂B₁₀H₁₂, respectively, demonstrating a higher probability of fluoro decaboranes for reaction with lithium. The obtained results not only explain the effect of position and number dependence of substituted fluoro atom(s) in B₁₀H₁₄ and Li@B₁₀H₁₄ but also elucidate a synergistic behavior to polarize a lithium excess electron for high NLO responses and vertical ionization potentials.