Year: 2026
Type: preprint
Abstract: Achieving cryogenic mechanical flexibility and persistent phosphorescence simultaneously is challenging because cooling suppresses molecular motion, favoring long-lived emission while limiting the structural adaptability required for elastic deformation. Alkynyl-engineering enables the C≡C unit to function beyond its conventional role as a conjugated linker, with directional C≡C···π-hole interactions serving as a key determinant of crystal packing and mechanical response. Three positional isomers, p-TPA-TRZ, m-TPA-TRZ, and o-TPA-TRZ, were designed to examine how molecular geometry controls this interaction topology while retaining the same TPA donor, TRZ acceptor, and alkynyl linker. These isomers yield six distinct single crystal forms, each exhibiting unique packing structures, emission properties, and mechanical responses. Flexible crystals consistently display C≡C···π-hole contacts that extend into alkynyl-directed interaction networks, whereas the non-flexible crystals lack this topology. The results demonstrate that specific intermolecular interactions can generate emergent crystal-level mechanical behavior through their geometric organization and propagation across the lattice. Remarkably, the flexible crystals retain their mechanical adaptability at 77 K, with persistent phosphorescence. These results establish a molecular-tocrystal design principle in which alkynyl-directed C≡C···π-hole interactions organize crystal packing to generate emergent cryogenic elasticity and persistent phosphorescence.
Source: ChemRxiv
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
Awards: G2352013663, G4265472287, G8048755570
OpenAlex ID: W7214070830