Abstract
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 (beta(0)) values as large as 181 624, 133 199, and 32 314 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 (Delta H-r degrees) at 298 K for B10H14 and its lithium/fluor derivatives highlight the changes in their thermodynamical aspects. The calculated enthalpies of lithiation reactions are -10.04, -11.29, and -13.18 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.