A dimethylbarbituric acid-based donor-acceptor molecule for blue-shifted mechanochromic luminescence

Mechanochromic luminescent materials activated by the direct and benign stimulus of mechanical force, hold significant promise for sensing and security technologies. While common mechanochromic luminescent materials typically exhibit a red shift in emission, blue-shifted mechanochromic luminescent materials remain rare, with their underlying design principles and mechanisms being less understood. Herein, a novel donor-acceptor compound, BA-DB , is designed and synthesized from dimethylbarbituric acid and 4-(dimethylamino)benzaldehyde. The solvatochromic trends in both absorption and emission spectra substantiate the intramolecular charge transfer character of BA-DB molecule. Single-crystal X-ray diffraction analyses confirm that robust non-covalent interactions, including C–H⋯O, C–H···π, and dipole-dipole forces, govern the highly periodic crystalline framework of BA-DB . BA-DB crystals exhibit a distinct blue-shifted mechanochromic luminescence, showing an emission peak shift of 41 nm from red to orange upon grinding. Experimental results reveal that the mechanical force disrupts key intermolecular interactions, which triggers a rearrangement of the molecular packing and crystal structure, ultimately leading to the blue-shifted emission. This work establishes a blue-shifted mechanochromic luminescent model based on a donor-acceptor design strategy, thus providing deeper insight into the correlation between molecular structure and emission properties.