The DFT Revelation of Optical Properties for Solid-State Anthracene Chalcone Compounds Containing Halogen Groups Modulated by a Charge Transfer Cocrystal Strategy

Four charge transfer cocrystals of anthracene chalcone compounds containing halogen groups were designed and prepared based on the π···π interactions. Four cocrystals were stacked in the identical D···A···D···A···D···A mode, with electron-rich anthracene chalcone compounds as donors (D) and electron-deficient 1,2,4,5-benzenetetracarbonitrile (TCNB) as the acceptor (A). The successful preparation of cocrystals was confirmed by PXRD and FT-IR tests, and the optical properties of the cocrystals were characterized by solid-state UV and fluorescence tests. Compared with the donors, the UV absorption bands of the four cocrystals had widened to the red region. A significant red shift appeared in the fluorescence emission peaks of the four cocrystals, and the emission quantum yield and fluorescence lifetime were significantly improved. Based on the obtained SXRD crystal data, detailed density functional theory (DFT) calculations were employed to analyze the weak intermolecular interactions in four cocrystals, and the π···π interactions were quantitatively analyzed to confirm the charge transfer effect. Under the influence of the charge transfer effect, the narrowing of the band gap for the four cocrystals induced the change in the transition dipole moment of the excited state, thus achieving modulation of the optical property. This study combines theoretical calculations and experiments to systematically reveal the conformational relationship between stacking modes and optical properties, which provides guidance for the development of novel optical materials.