The interaction between superalkalis (M3O, M = Na, K) and a C20F20 cage forming superalkali electride salt molecules with excess electrons inside the C20F20 cage: dramatic superalkali effect on the nonlinear optical property

Abstract

It is well known that electrides are a type of multielectron many-cage solid salt with excess electron anions inside the cages. The main concern regarding these structures is how to construct the organic single-caged electride molecules with an electron inside its cage. Using the perfluorinated fullerene cage C₂₀F₂₀ as the electron hole, the alkali metal atoms (M = Na, K) and superalkali atoms (M₃O, M = Na, K) with a smaller vertical detachment energy (VDE) value as the source of the electrons, we can construct new nonlinear optical (NLO) organic single-caged electride salt molecules M⁺(e@C₂₀F₂₀)⁻ and (M₃O)⁺(e@C₂₀F₂₀)⁻ due to the long-range charge transfer from the (super)alkali to inside the cage, forming an electron-hole pair within the molecule. To measure the nonlinear optical response, static first hyperpolarizabilities (β₀) and the superalkali effect on β₀ are exhibited for these new molecules. The β₀ values are 400 and 600 au for M⁺(e@C₂₀F₂₀)⁻ which are considerably smaller than 13 000 and 10 000 au for (M₃O)⁺(e@C₂₀F₂₀)⁻. It is revealed that the superalkali effect on the β₀ value is dramatic and the β₀ value increases by about 20–30 times. New single-caged superalkali electride salt molecules (M₃O)⁺(e@C₂₀F₂₀)⁻ possess not only a large nonlinear optical property but also higher stability. They hold potential as high-performance nonlinear optical materials.