Quasi-linear CuX2 (X = Cl, Br) motif-built hybrid copper halides realizing encouraging nonlinear optical activities

The emerging organic–inorganic hybrid metal halides feature unique optical and electronic properties, are easily grown and have flexible crystal structures, making them a class of promising next-generation nonlinear optical (NLO) and ferroelectric materials. Herein, we successfully synthesized two centimeter-level zero-dimensional copper halide organic–inorganic hybrids (C20H20P)CuX2 (X = Cl, Br) that are crystallized in the monoclinic noncentrosymmetric P21 space group. Their structures contain rare quasi-linear [CuX2]– anions and [C20H20P]+ cations. (C20H20P)CuCl2 and (C20H20P)CuBr2 crystals show phase-matchable NLO effects around 1.1 and 0.87 times that of benchmark KDP, respectively. These (C20H20P)CuX2 materials are the first NLO-active examples in the hybrid copper(I) halide family containing a quasi-linear CuX2 unit.