Water-stable zero-dimensional hybrid zinc halide modulated by π-π interactions: efficient blue light emission and third-order nonlinear optical response

Achieving multifunctional optimization of halide optical materials through the precise modulation of intermolecular interactions is highly significant, yet it faces considerable challenges. Here, we propose a strategy of pi-pi interactions microregulating to achieve the simultaneous optimization of multiple properties of halide optical materials. Using this strategy, we obtained a new lead-free zero-dimensional (0D) zinc halide [DPE]ZnCl4 (DPE = 1,2-di(4-pyridyl)ethylene), in which the protonated DPE cations are orderly arranged via pi-pi interactions, facilitating the ordered embedding and local regulation of [ZnCl4]2- units within long-range one-dimensional cationic pi-pi stacking. As a result of these modifications, [DPE]ZnCl4 exhibits efficient blue light emission with a high photoluminescent quantum yield (PLQY) of 18.55%, far exceeding that of corresponding organic salt halides. Furthermore, this compound demonstrates an enhanced third-order nonlinear optical (NLO) response, with the modulation depth and the third-order NLO absorption coefficient reaching 0.70 and 3.81 x 10-10 m W-1, respectively, surpassing those of three-dimensional (3D) perovskite quantum dots and most organic-inorganic hybrid halides. Notably, the modulation of pi-pi interactions results in a significant breakthrough in water resistance, allowing [DPE]ZnCl4 to maintain excellent structural and performance stability in water for a week. This innovative strategy of pi-pi interaction modulation provides new avenues for the multifunctional regulation and waterproof design of halide optical materials, and it is expected to advance the development and functionalization of stable halide optical materials.