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Fluorescence Color Modulation by Intramolecular and Intermolecular π−π Interactions in a Helical Zinc(II) Complex

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posted on 11.01.2005, 00:00 by Shin Mizukami, Hirohiko Houjou, Kenta Sugaya, Emiko Koyama, Hideo Tokuhisa, Takeshi Sasaki, Masatoshi Kanesato
When a fluorescent compound shows unique optical properties, an elucidation of the mechanism may lead to an important development of novel sensing strategies. A helical 3,3‘-di-tert-butylsalen−zinc(II) complex, [Zn2L12], has a red-shifted fluorescence as compared to that of [ZnL22], a half-structured mononuclear complex of [Zn2L12]; in addition, [Zn2L12] exhibits a fluorescence color change from green to light blue under external stimulations. We investigated the origins of these phenomena by spectroscopy, fluorescence lifetime measurement, fluorescence microscopy, X-ray powder diffraction, and X-ray single-crystal analysis. From the experimental data, we concluded that intramolecular and intermolecular π−π interactions are critical elements that determine the shifts of the fluorescence to a longer wavelength.