The organic co-crystals formed using naphthalenediimide-based triangular macrocycles and coronene: intermolecular charge transfers and nonlinear optical properties

• Published in: Physical chemistry chemical physics : PCCP Vol. 24; no. 48; pp. 29747 - 29756
• Main Authors: Wang, Li, Liu, Yan-Li, Wang, Mei-Shan
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 14.12.2022
• Subjects: Absorption spectra; Charge transfer; Crystallization; Crystals; Dispersion; Near infrared radiation; Nonlinear optics; Optical properties; Synthesis
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d2cp03236h

Formation of organic co-crystals is an effective strategy to synthesize near infrared emission and nonlinear optical (NLO) materials, which often show "1 + 1 > 2" performance. Moreover, the crystallization process can be effectively regulated through supramolecular interactions; thus the properties of co-crystal materials can also be flexibly regulated. Here, in order to further understand the nature and formation mechanism of co-crystals from the perspective of theoretical research, we studied the structures, intermolecular interactions, absorption spectra, charge transfer (CT) characteristics and nonlinear optical (NLO) properties of the newly synthesized organic co-crystals formed between naphthalenediimide based triangles (NDI, acceptor) and coronene (COR, donor). According to the analysis of decomposition of intermolecular interaction energy, dispersion energy played a major role, so the co-crystal properties can be regulated by regulating the intermolecular dispersion energy. More importantly, the formation of co-crystals NDI-COR and NDI-2COR reduced the E gap values with respect to those of their components. And there was significant intermolecular CT from COR to NDI and the degree of CT in NDI-COR was larger than that in NDI-2COR, so that the α tot and γ tot values of NDI-COR and NDI-2COR were significantly greater than those of their components. Thus, the NLO properties of organic co-crystals can be further improved by enhancing the electron-donating ability of the donor and the electron-withdrawing ability of the acceptor to enhance the degree of intermolecular interaction energy and CT. The second hyperpolarizability γ tot values of NDI-COR and NDI-2COR were significantly greater than those of their components, indicating that the formation of organic co-crystals between COR and NDI is an effective way to improve their NLO properties.