Synthesis And Recognition Properties Of Schiff Base And A Cationic Water-soluble Pillar[5]arenes Receptors

Ion recongniton plays an important role in the host-guest chemistry. It has been demonstrated that the arrival of any new chemosensors can accelerate the development of supramolecular chemistry and provide new opportunities for the sensor material science. Now days, thanks to the enthusiastic efforts of scientists, many good chemosensors were reported, and some design rules have been summarized. However, due to fluorescence quenching, the dependence on organic solvents or, more specifically, the interference from other anions, there are still major challenges to be overcome in developing highly selective chemosensors.In the first part, a bilateral Schiff base is reported for the colorimetric and fluorometric dual-channel sensing of Hg²⁺ ions by taking advantage of the hydrolysis of carbon-nitrogen double bond, altering an ICT state mechanism and then Hg²⁺ ions coordinated with amino moieties of 1,5-DAN and led to the aggregation of 1,5-DAN. Meanwhile, it formed a stable neutral complexes of amino-Hg-amino. In addition, test strips based on L were fabricated, which also exhibited a good selectivity to Hg²⁺ as in solution. This work provides a novel approach for the selective recognition of mercury ions. Notably, the color changes are very significant and all the recognition processes can be observed by the naked eye. We believe the test strips can act as a convenient and efficient Hg²⁺ test kits.In the second part, we developed a simple F--selective chemosensor system based on bilateral Schiff bases. Through study the single crystals of DMBS we could find the two naphthylene OH groups were intramolecularly hydrogen-bonded with the nitrogen atoms of the imine and C-H?π interactions of DMBS lead to the formation of two-dimensional sheets in the crystal lattice. The sensor DMBS could detect F- ions with high selectivity and sensitivity by the mechanism of photoinduced electron transfer（PET） and C-H?F- interactions. In addition, the obvious color changes and pronounced ON-OFF-type fluorescent signaling behavior can be seen by naked-eye.In the third part, we designed and synthesized a cationic water-soluble Pillar[5]arenes P. The Pillar[5]arene bearing ten trimethylamine groups, have demonstrate dintriguing recognition performance for some representative heavy metal cations including Fe³⁺, Fe²⁺, Ca²⁺, Zn²⁺, Cr³⁺, Mg²⁺, Na⁺, K⁺, Al³⁺, Co²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Ag⁺ and Hg²⁺. The recognition results revealed that the Pillar[5]arene was efficient and selective cation receptors for Ag⁺ over other selected cations. In addition,the complexation behavior of the Pillar[5]arene for Ag⁺ was also investigated by using NMR and UV–vis techniques. Detection limit of the method is 1.25×10^-5 M and binding constant is estimated with the Benesi–Hildebrand method and the value 0.95×10⁵ M^-1 indicates a fairly strong interaction between the Pillar[5]arene and Ag⁺.