Push–pull electron effects of the complexant in a Li atom doped molecule with electride character: a new strategy to enhance the first hyperpolarizability

Abstract

Differing from the reported strategy of push or pull electron effects of the complexant, a new strategy of the combination effects of both push and pull electrons of the complexant to enhance the first hyperpolarizability is performed with two Li atom doped complexants with a pair of difluorophenyl subunit rings. Large variance of the static first hyperpolarizabilities (β₀) are exhibited at the MP2/6-311++G(d,p) level. The order of the β₀ values is 2.9 ×10² (complexant UD) ≪ 5.9 × 10³ (LL) < 1.9 × 10⁴ (H-L) < 2.3 × 10⁴ (H_F-L) < 3.2 × 10⁴ (L-L) < 7.8 × 10⁵ a.u. (H_F-L_F). It is found that H_F-L_F with the edge-type push–pull electronic effect of the complexant has the largest β₀. The edge-type push–pull electronic effect brings a 2700 times increase in the β₀ from the UD to H_F-L_F structure. It shows that the push–pull electronic effect is a highly effective strategy to enhance the β₀ value. The β₀ (7.8 × 10⁵ a.u.) of the H_F-L_F is considerable, due to the small ΔE and the very large Δμ (18.085 a.u.), which comes from the corresponding long-range charge transfer transition. It is interesting that a pair of subunit rings of the complexant may have different electronic effects. In H-L and H_F-L_F, the left ring with a longer distance between Li and the subunit ring exhibits a push electronic effect, while the right ring with the shorter distance exhibits a pull electronic effect. This work may contribute to the development of potential high-performance nonlinear optical materials.