Herein, density functional theory (DFT) computations were performed to investigate the discrete dimer of a mono-substituted anthracene derivative (2-TA-AN), which exhibited highly efficient pure excimer fluorescence in its crystal form. As a more practical model, its geometry, potential energy curve and excited state property were systematically calculated to better understand the excimer formation process and photophysical properties. The compressed excimer geometry is responsible for the highly efficient excimer emission, arising from the enhanced rigidity that greatly suppresses its non-radiative vibrations. Potential energy curves along three directions reveal the non-uniqueness of excimer formation along the long axis of anthracene, which is in a good agreement with the experimental findings. Upon decreasing the displacement, the intermonomer charge-transfer (CT) component gradually increased towards an approximately equivalent hybridization with the locally-emissive (LE) state of the monomer during the formation of the excimer. The excimer emission wavelength versus intermonomer CT content shows a similar trend along the three directions, revealing a turning point related to the essential transition of the excited state properties from the LE of the monomer to the HLCT of the excimer. The present results will contribute to the better understanding of the structure-property relationships in excimer formation and photophysical properties.

In order to facilitate pyrene (PY) excimer formation in solids, several imidazole-containing PY derivatives were designed and synthesized. Among them, a new compound 1,4,5-triphenyl-2-(pyren-1-yl)-4,5-dihydro-1H-imidazole (IM-PY) was achieved with two crystalline...

Polyaromatic compounds are significant members of leading candidates for organic semiconductors and optical materials. However, a thorny problem of polyaromatic materials is that their good emissive abilities in solutions are seriously weakened in solids due to strong π−π interactions between aromatics. As a typical case, the intermolecular π−π interaction tends to form excimers for polyaromatic system, which were always considered to quench fluorescence and decrease luminous efficiency in the past decades. Herein, anthracene is modified by meta-substituted bromobenzene to facilitate the formation of discrete dimeric stack in solids, leading to the enhanced anthracene excimer fluorescence. Particularly, instead of excimer quenching fluorescence, the more anthracene dimers in solids, the higher fluorescence efficiency, namely, excimer-induced enhanced solid-state emission. This work not only provides a meta-substituted strategy for molecular design to form excimer in solids but also demonstrates that high-efficiency solid-state emission can be achieved by excimer species.

A novel mechanism of folding-induced spin–orbit coupling enhancement is responsible for the efficient room temperature phosphorescence of a thianthrene emitter.