Synthesis Of Novel Heterocyclic Receptors And The Recognition Properties

This paper includes four chapters:1. This one is about the research of cation recognition in recent years, whichcontain the following topica: (i) the principle of molecular recognition, thesignificance of cations recognition; (ii) the structural characteristics of cationsimpact on receptor design; (iii) receptors bearing thiol groups; (â…³) receptorsbearing phenolic hydroxy groups; (â…´) receptors bearing imino;2. Two simple mercapto thiadiazole‐based sensors were synthesized by aconvenient method. Their UV‐vis spectra were taken in DMSO‐H2O binary andHEPES buffered solutions. The sensing abilities both 1 and 2 toward various metalcations, such as Zn²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Fe³⁺, Hg²⁺, Ag+, Ca²⁺ and Cu²⁺, wereprimly investigated by UV‐vis spectroscopy. Upon addition of 2 equiv of Hg²⁺, sensor1 showed obvious changes in UV‐vis spectrum. Therefore, sensor 1 had a betterselectivity to Hg²⁺. Pleasantly, sensor 1 still could work well in aqueous solutioncontaining less than 30% organic solvent. By UV‐vis titration experiments, sensors 1and 2 reacted with Hg²⁺ to form stable complexes and the association constants Ka were4.4×10⁴ M^‐1 and 1.0×10³ M^-1. In (9.5:0.5, v/v) DMSO/H₂O HEPES (10 mM) bufferedsolutions at pH 7.20 for sensors 1 and 2. As a result, similar spectroscopic variationof the absorption band was found as above aqueous solutions. It should also benoted that the pH of the solution did not change during these experiments, clearlyexcluding any pH effects.3. Two novel colorimetric cation sensor bearing phenol, thiol and HC=N groupswas designed and synthesized. In a DMSO/H2O (9:1, v/v) solution, the sensorexhibited highly selective recognition of Cu²⁺ among a range of metal ions tested. Inthe presence of Cu²⁺, solutions of the sensor underwent a dramatic color changefrom colorless to yellow, while the presence of other metal cations such as Zn²⁺,Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Fe³⁺, Hg²⁺, Ag+ and Ca²⁺ had no effect on the color. Thedetection limit of the sensor toward Cu²⁺ is 8.0×10^‐7 M and an association constantK_a of 4.3×10⁵ M^‐1 was measured. The sensing of Cu²⁺ by this sensor was found to be reversible, with the Cu²⁺‐induced color being lost upon addition of EDTA.4. Two simple N‐phenyl‐ N′‐(2‐acetoxybenzoyl) urea derivates were sythesized.In a DMSO/H₂O (9:1, v/v) solution, the sensors exhibited highly selectiverecognition of Cu²⁺ among a range of metal ions tested. While the presence of othermetal cations such as Zn²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Fe³⁺, Ag⁺ , Ca²⁺ and Cu²⁺ had nosuch a change. By UV‐vis titration experiments, sensors reacted with Hg²⁺ to formstable complexes. The detection limit of the sensor toward Hg²⁺ is up to 10^‐6.Moreover, these compounds on plant growth have some regulatory role.