Fluorescent Switch Behavior of 1,2-Bis(4-pyridyl) Ethylene Controlled by pH in Aqueous Solution

• 作 者: ZOU Wen-sheng SHEN Qian-jin WA
• 机 构: College of Chemistry,School of Chemistry and Chemical Engineering
• 出 处: 高等学校化学研究（英文版）
• 发表日期: 2004年期
• 关键词: 1 2-Bis(4-pyridyl) ethylene Fluorescent switch pH fluorescence probe Cation-π in
• 基金项目: 国家自然科学基金

With the decrease of pH value from 8.45 to -1.0,the UV-Vis absorption and fluorescent spectra of 1,2-bis(4-pyridyl) ethylene(BPE) took on the same changing trend at four different successive pH stages: 8.45-7.20,7.20-5.62,5.62-2.60,and 2.60-1.0,namely,no change,decrease,increase,and decrease again.Among these,in a range of 7.20-5.62,the fluorescence wavelength blueshified from 418 to 359 nm,but the UV-Vis absorption wavelength,in contrast,redshifted from 285 to 298 nm.The fluorescence intensity of BPE had a drop even to quench upon a decline in the pH value from 2.60 to-1.0 probably owing to its cation-x interaction to reduce the π electron cloud density of BPE.Two dissociation constants,pKa1(4.30±0.01 ) and pKa2(5.65±0.04),were obtained based on fluorescence data.The changes of fluorescence spectra indicate that BPE has "off-on-off" switch behavior.The fluorescent spectra of BPE were nearly independent on the presence of α-and β-cyclodextrins.