Senthilvelan Annamalai, Ho I-Ting, Chang Kai-Chi, Lee Gene-Hsiang, Liu Yi-Hung, Chung Wen-Sheng
Department of Applied Chemistry, National Chiao-Tung University, Hsinchu, 30050, Taiwan, China.
Chemistry. 2009 Jun 15;15(25):6152-60. doi: 10.1002/chem.200802654.
We report herein a new ditopic calix[4]arene receptor 25,27-bis-{[4-amino-4-(1-naphthyl)-2-oxo-3-butenyl]oxy}-26,28-dihydroxycalix[4]arene (2) for the simultaneous complexation of anionic and cationic species. The host molecule 25,27-bis{[3-(1-naphthyl)-5-isoxazolyl]methoxy}-26,28-dihydroxycalix[4]arene (1) was synthesised first and was followed by a [Mo(CO)6]-mediated ring-opening reaction to give the target receptor 2. The binding properties of ligands 1 and 2 towards metal ions in CH3CN were investigated by UV/Vis and fluorescence spectroscopies. The results showed that both ligands 1 and 2 were highly selective for Cu(II) ions. Upon titration with Cu(II), the fluorescence of 1 was severely quenched, whereas 2 showed strong fluorescence enhancement because the metal ions help to lock the conformation of the fluorophores. During the complexation of 2 with Cu(II), the Cu(II) was reduced to Cu(I) by the free phenolic OH of 2, whereas the phenol was oxidised by Cu(II), after which it assisted in the trapping of Cu(I). Ditopic behaviour was observed for the complex 2.Cu(I), which showed further enhancement of its fluorescence intensity upon complexation with anions such as acetate or fluoride.
我们在此报告一种新型的双位点杯[4]芳烃受体25,27-双-{[4-氨基-4-(1-萘基)-2-氧代-3-丁烯基]氧基}-26,28-二羟基杯[4]芳烃(2)，用于同时络合阴离子和阳离子物种。首先合成主体分子25,27-双{[3-(1-萘基)-5-异恶唑基]甲氧基}-26,28-二羟基杯[4]芳烃(1)，然后通过[Mo(CO)₆]介导的开环反应得到目标受体2。通过紫外/可见光谱和荧光光谱研究了配体1和2在乙腈中对金属离子的结合性能。结果表明，配体1和2对Cu(II)离子都具有高度选择性。用Cu(II)滴定后，1的荧光严重猝灭，而2则表现出强烈的荧光增强，因为金属离子有助于锁定荧光团的构象。在2与Cu(II)络合过程中，2的游离酚羟基将Cu(II)还原为Cu(I)，而酚被Cu(II)氧化，之后它协助捕获Cu(I)。观察到络合物2·Cu(I)具有双位点行为，其与乙酸根或氟离子等阴离子络合后荧光强度进一步增强。
