The Bridge With ¦Â-cyclodextrin Host Molecule Synthesis, Characterization, And Their Guest Molecules Of Medicine, Pesticide Identification And Analysis Applications

Host compounds have high molecular recognition ability towards guest moleculesand their application open up broad prospects for developing the specific, exclusiveand highly selective methods to analyze guest molecules. In recent years, theapplications of new host compounds, such as prophyrin, crown ether, cyclodextrin(CD), and calixarence, on the recognition and analysis of bio-pertinent substanceshave gradually become the focal point of the present research work. Cyclodextrins have the hydrophobic cavity and hydrophilic wall. They are wellknown to have the property of forming inclusion complex with organic and inorganicmolecules which possess suitable polarity and dimension. So, as the excellent enzymemodel and molecules receptor, cyclodextrin have been widely used in a good many offields in science and technology. The formation of supramolecular complex withβ-CD can alter the photochemical and photophysical properties of the guest moleculesand considerable attentions have been focused on the luminescence application of thecyclodextrins.However, the inclusion by native CDs is less efficient and also specific, when wecompare them with natural systems such as enzymes or antibodies. Chemicalmodification of CD would be essential in order to improve its inclusion ability. It iswell-documented that tethering two cyclodextrin moieties width a short linker groupgreatly enhances the original molecular binding ability of the parent cyclodextrinthrough the cooperative binding of one guest molecule in the closely located twocyclodextrin cavities.Based on the changes in the spectrum characters of guest molecules producedthrough inclusion formation with bridged cyclodextrins, we have carried out twoaspect of investigation:Fist, A β-cyclodextrin (β-CD) dimer, containing two β-CD moieties that are linkedthrough their sides by disulfides was synthesized. The dimer was characterized bymeans of IR, ~1H NMR and elemental analysis. The new methods with high sensitivityfor the determination of guest molecules in bulk aqueous solution have beenestablished based on the significant enhancenment in the fluorescence intensity ofguest molecules produced through complexation with β-CD dimer. In this paper,utilizing the supramolecular interactions between host and guest, the sensitivespectrofluorimetry for determination of dequalinium chloride and mefenacet inaqueous solution by using β-CD dimer as sensitizing reagent have been reported. Theinterference experiments showed that these methods had good selectivity. Theapplication of the proposed methods to the determination of the analyzed substancesgave satisfactory results.Second, an ethylenediamine linked β-CD dimer was synthesized. The dimer wascharacterized by means of IR, 1H NMR and elemental analysis. The mechanisms forthe host-guest recognition have been studied, such as the interactions between β-CDdimer and tranilast, berberin hydrochloride. The formation of slupramolecularcomplex between β-CD dimer and analyzed substances were discussed. The essentialreason for the sensitization induced by β -CD dimer towards guest fluorenscence hasbeen further illuminated through fluorescence increasing experiments. The applicationof the proposed methods to the determination of the analyzed substances in serumgave satisfactory results.