Synthesis Of Sulfonic Calix[4]Arene Derivatives And Their Recognition To Metal Ions

With the rapid development of industry,environmental contamination caused by discharging of heavy metals has become an urgent problem to be solved.As the third generation of supermolecular parent,calix[n]arene possesses an electron-rich structure,and is easy to be modified on the upper and lower rim of calix[n]arene for introducing diverse functional groups.Up to now,a large number of calix[n]arene derivatives with the properties of separation and test metal ions have been reported in literatures.However,low solubility of calix[n]arene derivatives limits the studies and application of them in aqueous solution.In this paper,synthesis of water soluble sulfonic calix[4]arene derivatives with different substitution degree of sulfonic acid groups and their recognition to metal ions in aqueous solution have been studied on the basis of our previous work,which could provide a helpful data support for investigation on separation and test metal ions using calix[n]arene derivatives.(1).25,27-di(ethoxycarbonyl methoxy)-26,28-dihydroxyl calix[4]arene(compound 2)was synthesized by multiple steps reaction of polymerization and cyclization,reverse Friedel-Crafts alkylation and Williamson etherification using p-tert-butylphenol as starting material.Then,25,27-bis(hydrazidoylmethoxy)-26,28-dihydroxy calix[4]arene(compound 3)which was the product of compound 2 reacting with hydrazinium was sulphonated by concentration sulphuric acid in acetic acid medium to produce 5,17-disulfonic acid-25,27-bis(carboxymethoxy)-26,28-dihydroxy calix[4]arene(compound 5).Compound 2 underwent sulphonation reaction as mentioned above to produce compound 5 also.5,11,17,22-tetrasulfonic acid-25,27-bis(carboxymethyloxy)-26,28-dihydroxy calix[4]arene(compound 4)was obtained by reaction of compound 2 with concentration sulphuric acid.The synthesis,separation and purification of the two compounds were studied and their chemical structures were characterized by 1H NMR,13C NMR,MS and FT-IR,confirming compound 4 and compound 5 to be target molecules.(2).The effects of pH on the Ultraviolet absorption spectrum of target molecules were studied,and the recognitions of target molecules to 11 kinds of metal ions(Ca2+Mn2+,Cu2+,Zn2+,Cd2+,Co2+,Mg2+,Ba2+,Ni2+,Pb2+ and K+)were carried out by using of UV-Vis spectroscopy.Result showed that the absorption maximum wavelengths of compound 4 and compound 5 didn't shift within pH range studied.In pH range of 2.5-5.0,there were no noticeable effects of pH on ultraviolet absorption spectrum of compound 4;then,the absorption intensity increased obviously when pH exceed 5.5.Likewise,in pH range of 2.5-6.0,there were no noticeable effects of pH on ultraviolet absorption spectrum of compound 5;and absorption intensity increased obviously when pH exceed 6.5.After adding 11 kinds of metal ions mentioned above with the same concentration to compound 4 and compound 5 separately,absorption intensity at absorption maximum wavelengths of compound 4 and compound 5 increased 100%and 20%,respectively,when Cu2+ had been added,and no noticeable changes has been observed when other metal ions had been added.The results indicated that compound 4 and compound 5 could possess the ability to recognize Cu2+.(3).The recognition performances of both target molecules to 11 kinds of metal ions in aqueous solution were studied by using of fluorescence spectrometry.Result showed that Cu2 could quench the fluorescence of compound 4,decreasing 30.4%of fluorescence intensity.The reciprocal of fluorescence intensity difference 1/(AF)vs reciprocal of concentration of Cu2+(1/c)appeared good linear,indicating 1:1 of stoichiometric ratio of the guest compound 4 and host Cu2+,and inclusion constant was calculated to be 1.07×104 L·mol-1.Cu2+,Mn2+ and Pb2+ could quench the fluorescence of compound 5 also,decreasing 47.3%,86.1%and 88.6%of fluorescence intensity,respectively.Both reciprocal of fluorescence intensity difference 1/(?F)vs both reciprocal of concentration of Pb2+ and Mn2+(1/c)appeared good linear,indicating both 1:1 of stoichiometric ratio of the guest compound 5 and host Pb2+ and Mn2+,respectively,and inclusion constants were calculated to be 1.2×102 L·mol-1 and 9.6×102 L·mol-1,respectively.(4).Molecule assembling between compound 5 and triethylenetetramine was studied,and separation and purification of the product(compound 6)were done also.Result of 1H NMR showed that compound 6 was a kind of polymer salt forming by 1:2 of stoichiometric ratio of compound 5 and triethylenetetramine;and result of IR indicated that both carboxyl and sulfonic acid groups in compound 5 formed corresponding salts groups.Interaction between compound 6 and Cu2+ was studied.Results showed that different reaction condition caused different reaction sites between compound 5 and triethylenetetramine;both carbonyl and amino groups in compound 6 could interact with Cu2+.