High Sensitivity Viologen for a Facile and Versatile Sensor of Base and Solvent Polarity in Solution and Solid State in Air Atmosphere

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• 作者：Wei Shi ; Feifei Xing ; Yue-Ling Bai ; Meiling Hu ; Yongmei Zhao ; Ming-Xing Li ; Shourong Zhu
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：July 8, 2015
• 年：2015
• 卷：7
• 期：26
• 页码：14493-14500
• 全文大小：491K
• ISSN：1944-8252

文摘

Viologen cations are excellent electro- and photochromic materials. They generally have no response or very low sensitivity to bases. In this paper, three compounds, 1,1鈥?bis(2-oxo-2-phenylethyl)-4,4鈥?bipyridinium (viologen) with different substituents, including H (1), Cl (2), and OH (3), were synthesized. All three, especially 1 and 2, have very high sensitivity to base in both solution and solid state in air atmosphere. These viologens are responsive not only to bases but also to solvent polarity. NMR shows 1 became enolic and then a radical, whereas 3 is colored only in the radical form. These results are in agreement with EPR spectra. Crystal structures show that the C鈥揅 that links two pyridinium and N鈥揅 distances in coplanar pyridinium in the colored (radical) form is clearly longer than that of the pale-yellow form, indicating that the color is due to the viologen radical. Viologens containing an electron-withdrawing phenacetyl group are the most sensitive compounds for fast, naked eye detection of base and solvent polarity.