Chen Yin-Ju, Chen Meng-Yu, Lee Kun-Ti, Shen Li-Ching, Hung Hao-Chih, Niu Hao-Che, Chung Wen-Sheng
Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan.
Front Chem. 2020 Nov 12;8:593261. doi: 10.3389/fchem.2020.593261. eCollection 2020.
We report here the synthesis of a 1,3-alternate calix[4]arene , with bis-pyrazolylmethylpyrenes on the one end and bis-triazolylmethylphenyls on the other end, as a homoditropic fluorescent sensor for both Hg and Ag ions. Calix[4]arene , with lower-rim bis-pyrazolylmethylpyrenes in cone conformation, was also synthesized as a control compound. UV-Vis and fluorescence spectra were used for metal ions screening, and we found that both ligands and showed strong excimer emission of pyrenes when they are as a free ligand in CHCl/MeOH (v/v, 3:1) solution; however, they both showed a high selectivity toward Hg and Ag ions with strong fluorescence quenching and yet with different binding ratios. The fluorescence of ligand was strongly quenched by Hg but was only partially quenched by Ag ions; however, the fluorescence of ligand was strongly quenched by Hg, Ag, and Cu ions. Job plot experiments showed that ligand formed a 1:2 complex with both Hg and Ag ions; ligand formed a 1:1 complex with Hg, but it formed a 2:3 complex with Ag. The binding constant of ligand with Hg and Ag ions was determined by the Benesi-Hildebrand plot of UV-vis titration experiments to be 2.99 × 10 and 3.83 × 10 M, respectively, while the association constant of ligand with Hg and Ag was determined by Hill plot to be 1.46 × 10 and 9.24 × 10 M, respectively. Ligand forms a strong complex with either two Hg or two Ag ions using both the upper and lower rims of the 1,3-alternate calix[4]arene as the binding pockets; hence, it represents one of the highly selective fluorescent sensors for the homoditropic sensing of Hg and Ag ions.
我们在此报告一种1,3 -交替杯[4]芳烃的合成，其一端为双吡唑基甲基芘，另一端为双三唑基甲基苯基，作为一种对汞离子和银离子均具有同型双向荧光传感作用的传感器。还合成了杯[4]芳烃，其下边缘的双吡唑基甲基芘呈锥状构象，作为对照化合物。利用紫外可见光谱和荧光光谱对金属离子进行筛选，我们发现当两种配体在CHCl/MeOH（体积比3:1）溶液中作为游离配体时，均表现出芘的强激基缔合物发射；然而，它们对汞离子和银离子均表现出高选择性，伴有强荧光猝灭，但结合比例不同。配体的荧光被汞强烈猝灭，但仅被银离子部分猝灭；然而，配体的荧光被汞、银和铜离子强烈猝灭。Job曲线实验表明，配体与汞离子和银离子均形成1:2络合物；配体与汞形成1:1络合物，但与银形成2:3络合物。通过紫外可见滴定实验的Benesi - Hildebrand图测定，配体与汞离子和银离子的结合常数分别为2.99×10和3.83×10 M，而通过Hill图测定，配体与汞和银的缔合常数分别为1.46×10和9.24×10 M。配体利用1,3 -交替杯[4]芳烃的上下边缘作为结合口袋，与两个汞离子或两个银离子形成强络合物；因此，它是用于汞离子和银离子同型双向传感的高选择性荧光传感器之一。
