Uncovering the Intramolecular Emission and Tuning the Nonlinear Optical Properties of Organic Materials by Cocrystallization

• Published in: Angewandte Chemie International Edition 2016-11, Vol.55 (45), p.14023-14027
• Main Authors: Zhu, Weigang, Zhu, Lingyun, Sun, Lingjie, Zhen, Yonggang, Dong, Huanli, Wei, Zhixiang, Hu, Wenping
• Format: Article
• Language: English
• Subjects: cocrystals; density functional theory; nonlinear optics; Optical properties; organic crystals; photophysics
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201607712

The spectroscopic and photophysical properties of organic materials in the solid‐state are widely accepted as a result of their molecular packing structure and intermolecular interactions, such as J‐ and H‐aggregation, charge‐transfer (CT), excimer and exciplex. However, in this work, we show that Spe‐F4DIB cocrystals (SFCs) surprisingly retain the energy levels of photoluminescence (PL) states of Spe crystals, despite a significantly altered molecular packing structure after cocrystallization. In comparison, Npe‐F4DIB cocrystals (NFCs) with new spectroscopic states display different spectra and photophysical behaviors as compared with those of individual component crystals. These may be related to the molecular configuration in crystals, and we propose Spe as an “intramolecular emissive” material, thus providing a new viewpoint on light‐emitting species of organic chromophores. Moreover, the nonlinear optical (NLO) properties of Npe and Spe are firstly demonstrated and modulated by cocrystallization. The established “molecule‐packing‐property” relationship helps to rationally control the optical properties of organic materials through cocrystallization. Luminescent halogen‐bonded solids: Two new halogen‐bonded cocrystals were prepared and characterized for their crystal structure, self‐assembling manner, spectroscopic, photophysical, and nonlinear optical properties. The molecule‐packing‐property relationship helps to rationally design and prepare cocrystals with desired properties.