Design a novel type of excess electron compounds with large nonlinear optical responses using group 12 elements (Zn, Cd and Hg).

Based on the interesting Janus-type all-cis1,2,3,4,5,6-hexafluorocyclohexane (1) molecule, a novel type of excess electron compounds MF-1-MH (MF = Li, Na and K, MH = Zn, Cd and Hg) were designed theoretically. The geometric structures, electronic structures and nonlinear optical properties of MF-1-MH compounds were studied by density functional theory. Our results show that in Li-1-MH, the obvious charge transfer between Li and MH can be observed while in Na/K-1-MH, the charge transfer between Na/K and MH is negligible. Particularly, the MF-1-MH exhibit remarkable nonlinear optical (NLO) response and the first hyperpolarizability of the K-1-Zn almost achieve 1.0 × 106 au. We hope this work will further enrich the family of excess electron compounds, so that more experimental interests and efforts can be attracted to propose and synthesize new excellent NLO materials.