Rational Design of Charge-Transfer Interactions in Halogen-Bonded Co-crystals toward Versatile Solid-State Optoelectronics

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• 作者：Weigang Zhu ; Renhui Zheng ; Yonggang Zhen ; Zhenyi Yu ; Huanli Dong ; Hongbing Fu ; Qiang Shi ; Wenping Hu
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：September 2, 2015
• 年：2015
• 卷：137
• 期：34
• 页码：11038-11046
• 全文大小：597K
• ISSN：1520-5126

文摘

Charge-transfer (CT) interactions between donor (D) and acceptor (A) groups, as well as CT exciton dynamics, play important roles in optoelectronic devices, such as organic solar cells, photodetectors, and light-emitting sources, which are not yet well understood. In this contribution, the self-assembly behavior, molecular stacking structure, CT interactions, density functional theory (DFT) calculations, and corresponding physicochemical properties of two similar halogen-bonded co-crystals are comprehensively investigated and compared, to construct an 鈥渁ssembly鈥搒tructure鈥揅T-property鈥?relationship. Bpe-IFB wire-like crystals (where Bpe = 1,2-bis(4-pyridyl)ethylene and IFB = 1,3,5-trifluoro-2,4,6-triiodobenzene), packed in a segregated stacking form with CT ground and excited states, are measured to be quasi-one-dimensional (1D) semiconductors and show strong violet-blue photoluminescence (PL) from the lowest CT₁ excitons (桅_PL = 26.1%), which can be confined and propagate oppositely along the 1D axial direction. In comparison, Bpe-F₄DIB block-like crystals (F₄DIB = 1,4-diiodotetrafluorobenzene), packed in a mixed stacking form without CT interactions, are determined to be insulators and exhibit unique white light emission and two-dimensional optical waveguide property. Surprisingly, it seems that the intrinsic spectroscopic states of Bpe and F₄DIB do not change after co-crystallization, which is also confirmed by theoretical calculations, thus offering a new design principle for white light emitting materials. More importantly, we show that the CT interactions in co-crystals are related to their molecular packing and can be triggered or suppressed by crystal engineering, which eventually leads to distinct optoelectronic properties. These results help us to rationally control the CT interactions in organic D鈥揂 systems by tuning the molecular stacking, toward the development of a fantastic 鈥渙ptoelectronic world鈥?