Syntheses Of Cis-and Trans-Dibenzo-30-Crown-10 Derivatives And Their Complexations With Paraquat And Diquat

This Master's degree dissertation mainly studied the syntheses of cis-and trans-DB30C10-based derivatives(including diols and crytands)and their complexation with paraquat and diquat.1.Isomeric cis-and trans-DB30C10 diols were successfully synthesized regiospeciflcally with good yields,avoiding the difficult problem of separation of the two isomers' precursors diesters.Because trans-DB30C10 diester has 6 more atoms in its polyether macroring than trans-DB24C8 diester has,the reported method for the preparation of trans-DB24C8 diester fell in the trouble of the exclusive formation of smaller macrocycle carbomethoxybenzo-15-crown-5 when it was used for the synthesis of trans-DB30C10 diester.The synthetic routes of the two hosts as a whole have atomic economy because the side product,of benzylation of methyl 3,4-dihydroxybenzoate was used in the preparation of trans-DB30C10 diester.2.From the comparison of K_a values of two crown ethers with two guests,we found that the big differences(44 or 18 times)between the K_a value of the 1·3(or 2·3) and 1·4(or 2·4)in acetone suggested high selectivity of 1(or 2)to bind diquat 4 against paraquat 3.This indicated that the DB30C10 cavity can be used for the preparation of chemical sensors which can selectively detect diquat against paraquat.3.From the investigation of the influence of the addition of small molecules KPF₆ and DB18C6 on the complexations of either of crown hosts 1 and 2 with either of guests paraquat 3 and diquat 4,we found that the addition of KPF₆ could dissociate the complexes 1·3 and 2·3 completely and the subsequent addition of DB18C6 could reform these complexes completely.This reversible control makes DB30C10 derivatives and paraquat derivatives good candidate components for constructing molecular machines driven by adding small molecules.4.From the study of the complexation of two cryptand hosts with the two guests, we observed that the binding constants with the same guest were much higher than the corresponding simple crown ethers.This indicates that these crytands and the guests can be properly modified and then used for constructing advanced supramolecular structure such as supramolecular polymers.Besides,in solid state,one cryptand complexes diquat to form a pseudoroataxane,which indicates the complex can be used as a unit for fabricating molecular shuttles.