Halogenated (F, Cl, Br, or I) Diphenylhexatrienes: Crystal Structures, Fluorescence Spectroscopic Properties, and Quantum Chemical Calculations

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• 作者：Yoriko Sonoda ; Midori Goto ; Yuki Matsumoto ; Yukihiro Shimoi ; Fumio Sasaki ; Akihiro Furube
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：July 6, 2016
• 年：2016
• 卷：16
• 期：7
• 页码：4060-4071
• 全文大小：623K
• 年卷期：0
• ISSN：1528-7505

文摘

A series of halogenated compounds, (E,E,E)-1,6-di(4-X-phenyl)hexa-1,3,5-trienes (1: X = F, 2: X = Cl, 3: X = Br, 4: X = I), were synthesized and their crystal structures and fluorescence emission properties were systematically investigated. Single-crystal X-ray analysis reveals that molecules are arranged via X/X halogen bonds and/or CH/X-type hydrogen bonds to form a herringbone structure in 1 and π-stacked structures in 2–4. In the structures of 2 and 3, which are almost isomorphous, the distance and displacement for the nearest stacking molecules are smaller than those in 4. Although the structures of 2–4 are basically not greatly different from each other, the nearest-neighbor arrangements are π-stacked in 2 and 3, but herringbone in 4. Steady-state and time-resolved measurements show that the solid-state fluorescence properties also strongly depend on the halogen size. The fluorescence spectra are red-shifted and the Stokes shifts are large in 2 and 3 relative to those in 1 and 4, resulting from the difference in molecular arrangement in the crystal structure. The experimentally observed clear correlation between crystal structure and optical transition energy is reproduced fairly well by quantum chemical calculations for the excited states of molecular pairs in the X-ray determined structures of 1–4.