Study On The Recognition And Bonding Behavior Of P-sulfonated Calix[n]Arenes With Guest Molecules

Calixarenes, as the third generation of host molecules, have attracted considerable attention in host-guest chemistry because of their excellent recognition ability. Calixarenes with specific functions have been studied extensively as a platform for constructing novel host compounds. These host molecules have a cavity-shaped structure that can hold a guest molecule and create specific affinity to a target molecule by introducing various functional groups. Studies have investigated p-sulfonated calix[n]arenes, which have flexible and often defined cavities that bind positively charged species. One of the most important water-soluble calixarene derivatives-sulfonated calixarenes, they will cater to the molecular size and access to many of the inclusion compound because of more flexible structure. We synthesized three kinds of p-sulfonated calixarenes and took this as the foundation and discussed the inclusion behavior and the inclusion complex formation mechanism between sulfonation calixarene and various guest molecules by means of various methods in this paper. Taking advantage of this strong inclusion ability, p-sulfonated calixarenes were used to the inclusion toxic molecules. The results show p-sulfonated calixarenes could improve the utilization rate ofdrug molecules and provide a theoretical basis for detoxificationfunction. This thesis focuses on following parts:The first part briefly discusses the history of supramolecularchemistry and the research progress of up and lower edge ofcalixarene and the calixarene derivatives. It focuses on thesupramolecular recognition progress of sulfonated calixarenes withthe cation, anion and organic molecules guest. It evaluated theresearch in the hosts with molecular recognition and assemblyaspects. At the same time, it put forward the main contents of thisthesis.The second part studies the inclusion behavior and bonding typeof two kinds of N-substituted derivatives of tryptophan:N-[(tert–butoxy) carbonyl]-tryptophan (N-Boc-L-trp) andN-carbobenzoxy\-tryptophan (Z-trp-OH) with three kinds of sulfonatedcalixarene host compounds by fluorescence titration system, and putforward the hypothesis of the tert butyl and phenyl steric effect.1HNMR and density functional theory results reconfirmed theinclusion mechanism. It discusses molecular selective inclusion andtheir thermodynamics origin from the cavity sizes of hosts andstructures of guests. It is proved that the hypothesis was true. Theresults show the inclusion behavior caused by the inclusion ratio of1:1and rise from enthalpy change. According to the steric hindrancetheory of the different functional groups, Steric hindrance of thetert-butyl group of N-[(tert–butoxy) carbonyl]-tryptophan should bebigger than the phenyl group of N-carbobenzoxy-tryptophan, then theinclusion degree of N-[(tert–butoxy) carbonyl]-tryptophan with sulfonated calixarene will be much weaker thanN-carbobenzoxy-tryptophan with sulfonated calixarene. But thefluorescent experiment reaches the opposite conclusion, Whensulfonated calixarenes add to the guests, the fluorescence quenchingof N-[(tert–butoxy) carbonyl]-tryptophan are much bigger thanN-carbobenzoxy-tryptophan. So the inclusion degree naturally ismuch stronger. We propose that the inclusion are impossiblehappened in the tert butyl and benzyl position, the inclusion may beoccur in other groups of the guest. From the investigation ofthermodynamic origin, p-sulfonated calix [n] arene intend to includeN-[(tert–butoxy) carbonyl]–tryptophan. The guest molecular selectivewas mainly determined by the enthalpy contribution. The cavity sizeof every sulfonated calixarene is not the same. The larger is the cavitysize, the stronger is the inclusion ability of sulfonated calixarene bycavity matching effect. The binding constant between SCnA host andtwo tryptophan derivatives guest increases with the increasing of thecavity of the hosts, the host selective inclusion capacity: SC4A <SC6A <SC8A.The third part depicts that the tryptophan were determined byprepared sulfonating calixarene modified electrode, using cyclicvoltammetry, scanning speed is0.1V/s, the enrichment of voltage of+0.6V, the best molecule recognition of the tryptophan wasp-sulfonated calix [4] arene, followed by p-sulfonated calix [6] arene,finally sulfonated calix [8] arene. The linear range is1×10-7～1×10-5mol·L-1, and the detection limit is3×10-8mol·L-1. In order to moreclearly understand the tryptophan electrochemical behavior onsulfonated calix[n]arene modified gold electrode, the next section focuses on the research of supramolecular electrochemicalrecognition of tryptophan behavior on a p-sulfonated calix[4]arenemodified gold electrode. From EIS results, SC4A-cysteamine-goldelectrode showed the highest sensitivity, in terms of variation of Zreal value versus tryptophan concentration. The proposed methodcan also be used to detect tryptophan in real samples withsatisfactory results. The higher tryptophan sensitivity of SC4Acompared with SC6A and SC8A can be explained by their differencesin SCnA structures. SC4A rigid structure just meet the tryptophanmolecules, and permit tryptophan enter the inner part of the cavity.While SC6A and SC8A structure is more flexible than the SC4A and themolecular conformation often changes as they interacted with otherguests, the interaction in the tryptophan–SC4A complex was morestabilized than that in the tryptophan-SC6A (SC8A) complex.Molecular modeling calculation reconfirmed EIS results and indicatedthat the electrostatic interaction and the structural matching effectwere the dominant stabilizing factors for the host-guest complexes ofthe tryptophan and SCnA. At the same time charge interaction onbonding between the tryptophan–NH2+and sulfonated calixarenes–SO3also plays an indispensable rolet. These effects directly lead topolarization ability between SC4A and the tryptophan also increasing,thus the electrochemical impedance increases.The fourth part discusses the interaction of sulfonatedcalixarenes with colchicine using the electrochemical methods.Results show sulfonated calixarenes and colchicine both haveelectrochemical activity. When they interacted, the peak currentdecreased and the peak potential shifted positively, the phenomenon show the complex has no electrochemical activity. The reductionvalue of the peak current of colchicine shows a good linearrelationship with increasing sulfonated calix [4] arene concentrationswithin a certain range which confirmed that the1:1ratio complexassembly formed. The results showed a wide linear concentrationrange, low detection limit and high selectivity. UV spectrum resultsreconfirmed the inclusion ratio of1:1and presumably the inclusionsite may be in the phenyl ring. It was verified through the simulationresults of the lowest energy molecular model. The sulfonated calix [4]arene has good effects on solubilization of colchicine through theexperiment of colchicine solubilization and simulated cell membraneexperiments. The colchicine can be released from the sulfonatedcalix [4] arene and colchicines complex in sodium dodecyl sulfonatemicelle simulated cell membrane experiments, and entered into themicellar’s hydrophobic interior, which considered as a drug carrierwith colchicine.The fifth part discusses three sulfonated calixarene modifiedelectrode will be prepared to determine L-tyrosine. Not only thecurrent peak has obvious differences, the oxidation peak potentialsobviously move to more negative direction with cavity size smaller.The oxidation peak potential reduces, which makes the oxidationprocess easier, thus the electrochemical activity increases withaccelerating tyrosine electron transport rate on the surface of theelectrode. The modified electrode shows good catalytic ability of L-tyrosine oxidation reaction. The electrode has good selectivity andstability for the determination of tyrosine, there is a good linear rangeand low detection limit and high sensitivity at different concentrations under different pH. It established an accurate, fast,sensitive electrochemical method for the determination of tyrosine.The fluorescence spectra and1HNMR methods and computersimulation discuss p-sulfonated calix[n]arenes and tyrosine inclusionbehavior. P-sulfonated calix[n]arenes and tyrosine are all in thestoichiometric ratio of1:1subject-guest inclusion. The inclusion ismainly favorable enthalpy change caused by C-H…π or π…πinteraction of the p-sulfonated calix[n]arenes and tyrosine,accompanied by the unfavorable entropy of small change. The largeris the size of the cavity, the stronger the inclusion ability betweenp-sulfonated calix[n]arenes and guest. According to the results of1HNMR and cavity matching effect, presumably, the phenol unit oftyrosine enter into p-sulfonated calix[4]arene cavity, and the guesttyrosine molecule vertically penetrate into the cavity of p-sulfonatedcalix[6]arene in two different inclusion ways, tyrosine stably exists bythe way of lying on p-sulfonated calix[8]arene upper cavity. In view ofthis, the inclusion way of sulfonated calixarenes modified electrodeand sulfonated calixarenes solution with guest tyrosine is different,and supramolecular inclusion mode will change because of thechange of system.