Broad-spectrum light-induced bending, fracture, delamination, and jumping in a phenanthrene-modified barbituric acid crystal

Abstract

Sunlight-responsive organic crystals remain exceedingly rare due to the broad spectral distribution and low intensity of natural light. Herein, we report a yellow, needle-like crystal of a phenanthrene-modified barbituric acid derivative (DPPT) that exhibits photomechanical behaviors—including bending, fracture, and light-triggered jumping—under natural sunlight, white light, and monochromatic irradiation at 365 nm, 450 nm and 532 nm, with the unique additional feature of surface delamination occurring specifically under 365 nm UV light. Variable-time ¹H NMR spectroscopy, together with time-resolved PXRD and Raman analyses, revealed that these mechanical responses originate from light-induced conformational rearrangements within the DPPT molecules. Upon irradiation, surface-localized molecular rearrangement generates anisotropic internal stress, leading to backward bending, and under higher light doses, fracture induces crystal projection. In particular, the higher photon energy of 365 nm irradiation disrupts interlayer C–H⋯O interactions, giving rise to surface delamination prior to fracture. Notably, these complex motions are achieved in a single-component molecular system, without any need for interfaces, composites, or multilayer architectures. This work introduces a minimalist and efficient molecular design for achieving sunlight-driven actuation, offering a promising platform for the development of next-generation photomechanical actuators and intelligent light-responsive materials.