Assessing the Structure and First Hyperpolarizability of Li@B10H14 in Solution: a Sequential QM/MM Study Using the ASEC-FEG Method

The structure and electronic properties of lithium decahydroborate (Li@B10H14) complex in chloroform and water in normal thermodynamic conditions have been investigated using a sequential QM/MM calculations by means of the average solvent electrostatic configuration (ASEC) and the Free Energy Gradient (FEG) methods. To obtain the structure of Li@B10H14 complex in each of the solvents considered, we have performed geometry optimizations in solution using the ASEC-FEG method. The results show, for the first time with a realistic model of the molecular environment, that this alkali-metal-borane cluster is stable in chloroform but unstable in water. We have also explored the role of the electronic polarization of the solute due to solvent in the static first hyperpolarizability. The results show that in chloroform the electrostatic polarization effects is marked even so the Li@B10H14 complex displays a large electronic first hyperpolarizability, with potential for application as second-order nonlinear optical (NLO) material. In water, in contrast, the contribution of the excess electron for NLO response is significantly affected by the electrostatic polarization effects. Therefore our results reveal that the influence of environment must be considered in the design of new stable NLO materials.