Nitro-Substituted 4-[(Phenylmethylene)imino]phenolates: Solvatochromism and Their Use as Solvatochromic Switches and as Probes for the Investigation of Preferential Solvation in Solvent Mixtures

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• 作者：Leandro G. Nandi ; Felipe Facin ; Vanderl茅ia G. Marini ; Lizandra M. Zimmermann ; Luciano A. Giusti ; Robson da Silva ; Giovanni F. Caramori ; Vanderlei G. Machado
• 刊名：The Journal of Organic Chemistry
• 出版年：2012
• 出版时间：December 7, 2012
• 年：2012
• 卷：77
• 期：23
• 页码：10668-10679
• 全文大小：610K
• 年卷期：v.77,no.23(December 7, 2012)
• ISSN：1520-6904

文摘

Four 4-[[(4-nitrophenyl)methylene]imino]phenols (2a鈥?b>d) were synthesized. After deprotonation in solution, they formed the solvatochromic phenolates 3a鈥?b>d, which revealed a reversal in solvatochromism. Their UV鈥?/b>vis spectroscopic behavior was explained on the basis of the interaction of the dyes with the medium through combined effects, such as nonspecific solute鈥搒olvent interactions and hydrogen bonding between the solvents and the nitro and phenolate groups. Dyes 3a鈥?b>c were used as probes to investigate binary solvent mixtures, and the synergistic behavior observed was attributed to solvent鈥搒olvent and solute鈥搒olvent interactions. A very unusual UV鈥?/b>vis spectroscopic behavior occurred with dye 3d, which has in its molecular structure two nitro substituents as acceptor groups and two phenyl groups on the phenolate moiety. In alcohol/water mixtures, the E_T(3d) values increase from pure alcohol (methanol, ethanol, and propan-2-ol) until the addition of up to 80鈥?6% water. Subsequently, the addition of a small amount of water causes a very sharp reduction in the E_T(3d) value (for methanol, this corresponds to a bathochromic shift from 543 to 732 nm). This represents the first example of a solvatochromic switch triggered by a subtle change in the polarity of the medium, the color of the solutions being easily reversed by adding small amounts of the required cosolvent.