Can Coinage Metal Atoms Be Capable of Serving as an Excess Electron Source of Alkalides with Considerable Nonlinear Optical Responses?

Alkalides, as a representative kind of excess electron compounds, have been demonstrated to be potential nonlinear optical (NLO) materials with large static first hyperpolarizabilities (β). The possibility of utilizing coinage metal atoms as a novel excess electron source to design a series of alkalides, i.e., (M@3adz)M' (M = Cu, Ag, and Au; M' = Li, Na, and K), was examined by density functional theory calculations. The alkalide characteristics of these compounds are guaranteed by their HOMOs and VIE values as well as NBO analysis. In particular, all proposed alkalides exhibit considerable first hyperpolarizabilities (β) up to 61 590 au, indicating that they can be considered as novel NLO molecules of high performance. Moreover, a larger cage-complexant has been considered, and the resulting (Ag@TriPip222)K alkalide possesses a remarkably large β value of 180 068 au. We hope that this work will provide a new recipe for designing excess electron compounds and, on the other hand, attract more research interest and efforts in exploring new, unconventional alkalides.