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

Abstract

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.