Variable Mechanical Properties in Layered Copper Bromide Hybrid Solids Based on Configuration of Organic Cations

Organic-inorganic organohalide hybrid solids have garnered significant attention due to their unique structural diversity, desirable electronic structures, and excellent optoelectronic properties. Here, we investigate the mechanical properties of a homologous series of 2D copper bromide hybrids (A₂CuBr₄, ACuBr₄) through nanoindentation to analyze the contribution of organic interlayer interactions to bulk mechanical response. We identify a direct correlation between the identity of the organic spacer and the bulk mechanical response, where stronger bonding interactions in the organic interlayer resulted in increased hardness and elasticity. Additionally, we uncover a unique conformational dependence within the series of arylammonium spacers which was found to periodically modulate pi-pi interactions between neighboring molecules, leading to an alternating even-odd bulk material response.