Molecular insertion regulates the donor-acceptor interactions in cocrystals for the design of piezochromic luminescent materials

Abstract

Developing a universal strategy to design piezochromic luminescent materials with desirable properties remains challenging. Here, we report that insertion of a non-emissive molecule into a donor (perylene) and acceptor (1,2,4,5-tetracyanobezene) binary cocrystal can realize fine manipulation of intermolecular interactions between perylene and 1,2,4,5-tetracyanobezene (TCNB) for desirable piezochromic luminescent properties. A continuous pressure-induced emission enhancement up to 3 GPa and a blue shift from 655 to 619 nm have been observed in perylene-TCNB cocrystals upon THF insertion, in contrast to the red-shifted and quenched emission observed when compressing perylene-TCNB cocrystals and other cocrystals reported earlier. By combining experiment with theory, it is further revealed that the inserted non-emissive THF forms blue-shifting hydrogen bonds with neighboring TCNB molecules and promote a conformation change of perylene molecules upon compression, causing the blue-shifted and enhanced emission. This strategy remains valid when inserting other molecules as non-emissive component into perylene-TCNB cocrystals for abnormal piezochromic luminescent behaviors.

Piezochromic Tetracoordinate Boron Complex: Blue‐Shifted and Enhanced Luminescence

“…On exposure to DCM, the PL spectrum of Y‐phase crystalline powder redshifted to 591 nm with the orange fluorescence (Figure S11), which was very close to that of O‐phase crystals. Thus, it was speculated that the presence of solvent molecules may explain the redshift of PL spectra [5b, 11] …”

Enhanced luminescence of single-benzene fluorescent molecules through halogen bond cocrystals

“…With the development of supramolecular chemistry and crystal engineering, multi-component molecular materials such as cocrystals have been extensively studied. 12–17 Organic cocrystals are usually assembled by two or more different molecules in a clear stoichiometric ratio through non-covalent interactions, such as hydrogen bonds, halogen bonds, and π–π stacking interactions. 12,18,19 Cocrystal engineering can avoid complex synthetic procedures, and it is easy to manipulate non-covalent interactions between molecules to achieve adjustable functional properties, providing a good platform for revealing the structure–property relationship at the molecular level.…”

Unravelling supramolecular features and opto-electronic properties of a binary charge transfer cocrystal of a blue fluorescent di-carbazole and TFT

“…2 The scope of organic charge transfer cocrystals was initially limited to electronic applications; however, they have been recognized for multiple optical applications recently. Charge transfer cocrystals have been utilized for aggregation induced emission enhancement (AIEE), 3 white light emission, 4 two photon emission, 5 piezochromic emission enhancement, 6 room temperature phosphorescence, 7 thermally activated delayed fluorescence (TADF), 8 active optical waveguides, 9 optical data storage, 10 bio-imaging, 11 and stimuli responsive fluorophores. 12 Combining the intrinsic semiconductor nature with charge transfer emission in CT cocrystals makes them ideal candidates for organic light emitting transistors (OLETs) 13 and photoconductors.…”