Effect of Substituent Position in Coumarin Derivatives on the Interfacial Assembly: Reversible Photodimerization and Supramolecular Chirality

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• 作者：Zongxia Guo ; Tifeng Jiao ; Minghua Liu
• 刊名：Langmuir
• 出版年：2007
• 出版时间：February 13, 2007
• 年：2007
• 卷：23
• 期：4
• 页码：1824 - 1829
• 全文大小：266K
• 年卷期：v.23,no.4(February 13, 2007)
• ISSN：1520-5827

文摘

The Langmuir and Langmuir-Schaefer (LS) films of two coumarin derivatives, 4-octadecyloxylcoumarin (4-CUMC18) and 7-octadecyloxylcoumarin (7-CUMC18), were newly synthesized, and their interfacial assemblies wereinvestigated. Owing to the different substituent position of the long octadecyloxy chain in the coumarin parent, thetwo compounds showed completely different behaviors in the interfacial assemblies. When they were spread at theair/water interface, 7-CUMC18 formed a monolayer while 4-CUMC18 formed a multilayer film on the water surface.The spreading films on the water surface were transferred onto solid substrates by a Langmuir-Schaefer method, andthe transferred films were characterized by UV-vis, Fourier transfer infrared, X-ray diffraction, circular dichroism,and atomic force microscopy spectra. Different packing of the molecules in the multilayer films was observed. Whilecoumarin groups stacked in a face-to-face way in 7-CUMC18 film, they stacked in a head-to-tail manner in 4-CUMC18film. Furthermore, distinct properties of the multilayer films were observed. It is revealed that a reversible [2 + 2]photodimerization and photocleavage could be induced in the LS film of 7-CUMC18 under photoirradiation with UVlight of 365 and 254 nm, respectively. No photodimerization occurred in the 4-CUMC18 film. However, the film of4-CUMC18 showed a supramolecular chirality although the compound itself is achiral.