Design and synthesis of preorganized tripodal fluororeceptors based on hydrogen bonding of thiourea groups for optical phosphate ion sensing
作者:Shin-ichi Sasaki、Daniel Citterio、Satoru Ozawa、Koji Suzuki
DOI:10.1039/b105913k
日期:2001.11.29
Expecting a preorganization effect, tripodal anion host molecules were designed and synthesized. It was demonstrated that two kinds of new thiourea derivatives having a six-fold substituted benzene ring as a preorganized spacer were effective for recognition of the tetrahedral dihydrogen phosphate anion. A tripodal fluororeceptor 1 having a pyrene moiety adjacent to the thiourea binding site showed long-wavelength emission upon addition of guest anions in acetonitrile. On the other hand, a tripodal thiourea receptor 2 connected to anthracene groups via methylene units showed a decrease in fluorescence intensity upon addition of anions. In both cases, the degree of the change in emission intensity was in the order of H2PO4− > CH3COO− > Cl−
≫ ClO4−, which is clearly
different from that of reference compounds having only one binding site. Association constants (Ka) of these tripodal fluororeceptors also confirmed the dihydrogen phosphate selectivity over the more basic acetate anion in this homogeneous solution system. The characteristics of the fluororeceptors using the preorganization effect were shown to be promising for the development of chemical ion sensors with a specific anion selectivity.
预期存在前组织效应,设计并合成了三脚架型阴离子主体分子。研究表明,两种新型硫脲衍生物,其六取代苯环作为前组织间隔基,能有效识别四面体磷酸二氢根离子。具有吡啶并环部分与硫脲结合位点相邻的三脚架型氟光受体1在加入客体阴离子后,在乙腈中表现出长波长发射。另一方面,通过亚甲基单元与蒽基团相连的三脚架型硫脲受体2在加入阴离子后荧光强度降低。在这两种情况下,发射强度的变化程度依次为H2PO4^- > CH3COO^- > Cl^- ≫ ClO4^-,这与仅有一个结合位点的参考化合物明显不同。这些三脚架型氟光受体的结合常数(Ka)也证实了在该均相溶液系统中对磷酸二氢根离子相对于更基础的醋酸根离子的选择性。利用前组织效应的氟光受体特征显示出有望开发具有特定阴离子选择性的化学离子传感器。