Cation鈥揂nion Dual Sensing of a Fluorescent Quinoxalinone Derivative Using Lactam鈥揕actim Tautomerism

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• 作者：Yuta Nakane ; Takashi Takeda ; Norihisa Hoshino ; Ken-ichi Sakai ; Tomoyuki Akutagawa
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：June 18, 2015
• 年：2015
• 卷：119
• 期：24
• 页码：6223-6231
• 全文大小：467K
• ISSN：1520-5215

文摘

A quinoxalinone derivative capable of lactam鈥搇actim tautomerization was designed as a new fluorescence probe for sensing of cation (M⁺ = Li⁺ and Na⁺) and anion (X^{鈥?/sup> = F鈥?/sup>, Cl鈥?/sup>, Br鈥?/sup>, and CH₃COO鈥?/sup>) in organic solvents. In THF, the minor lactam tautomer exhibited a weak fluorescence band at 425 nm with a typical Stokes shift of 鈭?400 cm鈥?, whereas the major lactim tautomer exhibited an intense fluorescence band at 520 nm with large Stokes shift of 鈭?900 cm鈥? due to excited-state intramolecular proton transfer (ESIPT). The presence of either cations or anions was found to promote lactim-to-lactam conversion, resulting in the lowering of the ESIPT fluorescence. The lone pairs on the alkylamide oxygen and the quinoxalinone ring nitrogen of the lactam were found to bind Li+ to form a 1:2 coordination complex, which was confirmed by single crystal X-ray structural analysis and fluorescent titrations. In addition, the N鈥揌 bond of the lactam was able to recognize anions via N鈥揌路路路X hydrogen bonding interactions. Where X = F鈥?/sup> or CH₃COO鈥?/sup>, further addition of these anions caused deprotonation of the lactam to generate an anionic state, consistent with the crystal structure of the anion prepared by mixing tetrabutylammonium fluoride and the quinoxalinone derivative in THF. Dual cation鈥揳nion-sensing responses were found to depend on the ion-recognition procedure. The anionic quinoxalinone derivative and its Li+ complex, which are formed by the addition of CH₃COO鈥?/sup> and Li+, respectively, displayed different fluorescence enhancement behavior due to the two anions exchanging with each other.}