Side-Chain Engineering for Modulating Fluorescence and Mechanical Properties of Single Crystals

This is the authors' abstract. We don't add key points for this paper.

Molecular engineering of organic single crystals via minimal structural modification remains a key challenge in the development of multifunctional crystalline materials. A side-chain engineering strategy is reported for simultaneously regulating optical emission and mechanical adaptability in acetophenone derivatives: 2′-hydroxy-5′-methylacetophenone (HMAP) and 2′-hydroxy-5′-methoxyacetophenone (HMOAP). This approach enables unprecedented molecular-level control, facilitating concurrent modulation of optical emission with a notable shift (Δλ = 47 nm) through single substituent variation. Specifically, the fluorescence exhibits a notable blue shift from 552 nm (yellow, HMAP) to 505 nm (green, HMOAP). Distinct mechanical properties have been achieved, and HMAP single crystals exhibited two-dimensional plastic deformation when subjected to external force, whereas the elongated plate-like single crystals of HMOAP demonstrated two-dimensional elastic deformation under mechanical force, with elastic strains reaching up to 4.9% and 14.3%, respectively. Beyond their elastic limits, they experience permanent plastic deformation. Our findings establish a viable strategy for expanding the organic flexible single crystal system, enabling easy modulation of the single crystal properties.