Ionic liquids (ILs) are new and alternative solvent media that offers a unique solvation milieu due to ionic nature of their constituents. Proton-transfer involving a probe and its prototropic forms strongly depends on the nature of the solubilizing media. In this short communication, photophysical properties of 2-Naphthoic acid (2NA) in IL based media have been investigated with the help of electronic absorbance and steady state fluorescence spectroscopy. Fluorescence emission from 2-Naphthoate anion can be observed in neat 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) and 1-Butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]). Fluorescence emission from 2-Naphthoate anion can be quenched in presence of [bmim]⁺ cation of ionic liquids in presence of neutral/basic water whereas protonation of 2-Naphthoate anion takes place when acidic water is added to ionic solutions of 2-Naphthoic acid. Formation of non fluorescent complex takes place in excited state between 2-Naphthoate anion and ionic liquid cation [bmim]⁺ in presence of neutral/basic water. More specifically, presence of IL [bmim][BF₄] up to 5.0±0.1 wt% do not cause any change in the absorbance spectra of 2-Naphthoic acid dissolved in pH 12.0±0.1 water whereas significant fluorescence quenching is observed due to formation of non fluorescent complex in the excited state between 2-Naphthoate anion and IL cation [bmim]⁺. Excited state protonation of 2-Naphthoate anion can be achieved in [bmim][BF₄] by the addition of pH 2.0±0.1 phosphate buffer, whereas addition of pH 6.0±0.1 phosphate buffer causes decrease in fluorescence intensity. Fluorescence quenching of deprotonated form of 2-Naphthoic acid was also observed with the addition of 1M aqueous NaOH in [bmim][OTf] having same cation [bmim]⁺ as in IL [bmim][BF₄].

离子液体 (IL) 是新的替代溶剂介质，由于其成分的离子性质，可提供独特的溶剂化环境。涉及探针及其质子形式的质子转移在很大程度上取决于增溶介质的性质。在这篇简短的交流中，借助电子吸光度和稳态荧光光谱研究了基于 IL 的介质中 2-萘甲酸 (2NA) 的光物理特性。可以在纯 1-丁基-3-甲基咪唑鎓四氟硼酸盐 ([bmim][BF ₄ ]) 和 1-丁基-3-甲基咪唑鎓三氟甲磺酸盐 ([bmim][OTf]) 中观察到 2-萘甲酸阴离子的荧光发射。2-萘甲酸阴离子的荧光发射可以在 [bmim] ^{+ 的}存在下猝灭在中性/碱性水存在下离子液体的阳离子，而当酸性水加入 2-萘甲酸的离子溶液时，2-萘甲酸阴离子发生质子化。在中性/碱性水存在下，在 2-萘甲酸阴离子和离子液体阳离子 [bmim] ⁺之间以激发态形成非荧光复合物。更具体地说，IL [bmim][BF ₄ ] 高达 5.0±0.1 wt% 的存在不会导致溶解在 pH 12.0±0.1 水中的 2-萘甲酸的吸收光谱发生任何变化，而由于形成而观察到显着的荧光猝灭2-萘甲酸阴离子和IL阳离子[bmim] ⁺之间处于激发态的非荧光复合物。[bmim][BF ₄可实现2-萘甲酸阴离子的激发态质子化] 通过添加 pH 2.0±0.1 磷酸盐缓冲液，而添加 pH 6.0±0.1 磷酸盐缓冲液会导致荧光强度降低。通过在 [bmim][OTf] 中加入 1M NaOH 水溶液（具有与IL [bmim][BF ₄ ]中相同的阳离子 [bmim] ^{+ ）}，也观察到 2-萘甲酸的去质子化形式的荧光猝灭。