Nonlinear Optical Chemosensor for Sodium Ion Based on Rhodol Chromophore

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• 作者：Yevgen M. Poronik ; Guillame Clermont ; Mireille Blanchard-Desce ; Daniel T. Gryko
• 刊名：Journal of Organic Chemistry
• 出版年：2013
• 出版时间：December 6, 2013
• 年：2013
• 卷：78
• 期：23
• 页码：11721-11732
• 全文大小：617K
• 年卷期：v.78,no.23(December 6, 2013)
• ISSN：1520-6904

文摘

As part of a strategy to identify good fluorescent probes based on two-photon excited fluorescence (TPEF), the sensor for sodium cation has been designed bearing a rhodol chromophore linked with an aza-crown ether. An efficient synthetic route to rhodol derivatives possessing five-membered heterocycles at position 9 and their precursors that contain xanthylium salt has been developed. The synthesis involves condensation of xanthylium salts bearing vinamidinium moiety at position 9, with phenylhydrazine derivatives as the key step. To accomplish the synthesis of derivatives bearing 1-aza-15-crown-5 and 1,10-diaza-18-crown-6, the Buchwald鈥揌artwig reaction has been employed in the final stage. Electronic spectra of all prepared rhodols display strong absorption in the range of 450鈥?50 nm with well-resolved vibronic bands, which maintains its fine structure in a wide range of solvents. The most intensive two-photon absorption (2PA) band in the rhodol spectrum (165 GM), located at shorter wavelengths, matches well with the short-wavelength absorption band in the linear electronic spectrum and is most probably related to the two-photon allowed electronic transition S₀鈫扴₂. The influence of cation binding on one- and two-photon spectroscopic properties of rhodol linked with 1-aza-15-crown-5 via the phenylpyrazole bridge has been investigated. This probe exhibits high sensitivity and good selectivity for Na⁺ in CH₃CN. The mechanism involves the complexation of the Na⁺ by 1-aza-15-crown-5 in the probe, which induces prominent fluorescence enhancement via quenching of electron-transfer. Interestingly, the complexation with Na⁺ led to a significant increase of the 2PA band in the 750鈥?00 nm region (corresponding to a two-photon allowed, one-photon forbidden transition) for rhodol bearing 1-aza-15-crown-5, which led to the overall enhancement of the TPEF signal (approximately an order of magnitude). Thus, a turn-on fluorescent probe for sodium ion, which does not respond to many other metal species, has been constructed.