Highly Selective Protic-Solvent-Mediated Organic-Inorganic Hybrid Cuprous Bromides Achieving Structural Transformation

Abstract

The potential application of stimuli-responsive hybrid copper halides in information storage and switch devices has generated significant interest. However, their transformation mechanism needs to be further studied deeply. Herein, two zero-dimensional (0D) organic-inorganic hybrids, namely, (TBA)CuBr₂ (1) with linear [CuBr₂]^- units and (TBA)₂Cu₄Br₆ (2) with [Cu₄Br₆]^2- clusters (TBA⁺ = (C₄H₉)₄N⁺), are synthesized using simple solvent evaporation approaches. Interestingly, upon exposure to distinct protic solvents, such as methanol, ethanol, ethylene glycol, or hot water, 1 undergoes a transformation into 2 with varying degrees of transition, accompanied by a change in luminescence color from cyan to orange (or mixed color) under high-energy emission (e.g., 254 nm) excitation. Hot water can trigger 1 to completely transform into 2 because of its large contact angle difference in the solvents. Furthermore, 2 can be converted back to 1 through a simple solid-state mechanochemical reaction. Additionally, the structure of 2 remains unchanged even after immersion in 80 °C H₂O for 168 h due to the dense organic framework. This study provides valuable insights for exploring reversible structural transformation materials in the 0D metal halide system.