An External Electric Field Manipulated Second-Order Nonlinear Optical Switch of an Electride Molecule: A Long-Range Electron Transfer Forms a Lone Excess Electron Pair and Quenches Singlet Diradical

Abstract

An electride molecule e–···K(1)+···calix[4]pyrrole···K(2)+···e– as an external electric field (F) manipulated nonlinear optical (NLO) switch is designed theoretically for the first time. As this molecule is an unusual singlet diradical electride molecule with two easily driven excess electrons (by electric field) at two opposite ends of the molecule, a novel switching mechanism of electronic structure isomerization emerges as a distinctive nonbonding evolution in the electride molecule. A small electric field driving leads to a long-range excess electron transfer from one side K(1) through the middle calix[4]pyrrole to the other side K(2), forms a lone excess electron pair of s-type rather than a single bond, and quenches the singlet diradical. Meanwhile, the molecular electronic structure becomes K(1)+···calix[4]pyrrole···K(2)+···2e–. Therefore, the small electric field driving brings a very high static first hyperpolarizability (β0) contrast from 0 (F = 0, Off form) to 4.060 × 105 au (F = a small nonzer...