Study On The Interaction Of Different Guest Molecules With P-sulfonated Calix[n]arenes

Calixarenes are cup-shaped macrocycle hosts which arereadily available via the condensation of a para-substituted phenolwith formaldehyde, Due to their ability to construct multi-sitehydrogen bonding, specific stacking and generalized electrostaticinteractions, calixarenes have been exploited as impactful hostmatrices for guest molecules. The characteristics of host–guestcomplexations between p-sulfonated calixarenes and manydifferent kinds of guest molecules have been studied throughfluorescence、1H NMR spectroscopic、 molecular dynamicscalculations. The various factors affecting the inclusion processwere examined in detail and obtained interaction mechanism of theinclusion process. The work can provide certain theoretical methodfor further study of the interactions of other calixarenes with guest.The content of this paper is as follows:1. The Introduction Introduces the conformation of calixarene,derivatives, molecular self-assembly, molecular recognition as wellas the property of sulfonated calixarene.2. The characteristics of host–guest complexations betweenp-sulfonated calix[n]arenes (n=4,6,8) and Cocaine hydrochloride have been studied through fluorescence and1H NMR spectroscopic.It was found that the fluorescence intensity of Cocainehydrochloride quenched regularly upon the addition of p-sulfonatedcalix[n]arenes (n=4,6,8). A1:1stoichiometry for the complexationwas established and was verified by Job’s plot. Thetemperature-dependent inclusion constants were calculated.Meanwhile, the proposed interaction mechanism of the inclusioncomplex was discussed based on1H NMR and molecular modelingcalculations. The various factors (pH, ionic strength, concentration,temperature, the addition order of reagents, reaction time,surfactants) effecting the inclusion process were examined indetail.3. The inclusion interaction of1,10-Phenanthroline (phen) withp-sulfonated calix[n]arene (SCnA, n=4,6) is verified usingfluorescence spectrophotometry, thermodynamic parameters andmany other techniques. Influences of pH, temperature and theconcentration of SCnA (n=4,6) were examined in detail. Accordingto study Results, In phosphate buffer solution with pH6.0, thefluorescenc of1,10-Phenanthroline (phen) dramatically quenchedupon addition of SCnA (n=4,6) revealing the formation of inclusioncomplexes between phen and SCnA (n=4,6). Stability constantswere determined at different temperatures and pH levels byspectrofluorometry titrations, and the thermodynamic parametersof the obtained complex were identified. SC6A–phen complexformed the more stable than SC4A-phen.1H NMR titration spectratestified that phen may be penetrated into the hydrophobic cavity ofSCnA (n=4,6). This was confirmed by molecular dynamics calculations.4. The supramolecular interaction of astemizole withp-sulfonated calix[4]arenes were studied using spectrofluorimetry,1H NMR and molecular modeling calculations. A1:1stoichiometryfor the complexation was established and was verified by Job’s plotand1/(F–F0) versus1/[SC4A] of SC4A-astemizole complex. Theinteraction mechanism of the inclusion complex was discussed andthe various factors affecting the inclusion process were examinedin detail， such as SCnA concentration、 ionic strength、 pH、surfactants、 the addition order of reagents. It was found that thedramatic quenching of the fluorescence intensity of astemizole wasobserved with the addition of the SC4A. This was due to astemizolereact with SC4A to form stable complex.1H NMR titration spectratestified that astemizole reacted with SC4A. This finding wasconfirmed using1H NMR. This can also be proved by the molecularmodeling calculations.