Synthesis and applications of a series of new tripodal receptors under microwave conditions to be used for anion and cation recognation

Anions play a fundamental role in a wide range mainly in biology, medicine, catalysis and the environment. Design and synthesis of artificial receptors to use selective recognition of anionic species has attracted considerable interest in the past two decades. Recognition of anions and cations by artificial receptors is one of the fastest growing disciplines in the field of supramolecular chemistry. Use of microwave irradiation in organic chemistry has been widely studied in the last decades and a great deal of papers and reviews has shown that a variety of chemical transformation can be carried out successfully by microwave irradiation. Most importantly, microwave technique reduces reaction time and allows higher yield, less formation of side product, easier studying in accord with green chemistry protocols, solvent-free organic transformation, atom economy and selective reactions. In the scope of the study, firstly a series of amide based tripodal receptors was synthesized by using microwave irradiation. In the second stage anionic and cationic recognition properties of the tripodal receptors was investigated by using 1H NMR titration technique. In the first stage of the study; new group 1 chiral tripodal receptors containing amidoalcohol moiety on their side arms were synthesized. For this aim, Nitrilotriacetic acidwas reacted with five different (S)-(-)-aminoalcohols (R: Benzyl, phenyl, isopropyl, isobutyl, methyl) in 1:3 ratio under the optimum microwave conditions to give the chiral tripodal receptors in very high yields (≥90%) Nitrilotriacetic acid was reacted with 4-aminobenzo-15-crown-5 and 4-aminobenzo-18-crown-6, respectively, under the optimum microwave conditions in 1:3 ratios to give group 2 new tripodal receptors containing crown ether group on their side arms. In addition, group 2 new tripodal receptors were synthesized by the conventional way. In the second stage of the study, both anion and cation recognition (enantiomeric recognition) properties of all synthesized tripodal receptors were investigated by 1H NMR titration method with tetrabuthylammonium (TBA) salts of the anions (H2PO4- , HSO4-, C6H5CO2-, CH3CO2-, ClO4-, F-, Cl-, Br-) and with (R)-phenylethyl ammonium perchlorate (R-AM1), (S)-phenylethyl ammonium perchlorate (S-AM1), (R)-naphylethyl ammonium perchlorate (R-AM2), (S)-naphylethyl ammonium perchlorate (S-AM2) salts, respectively and the results were discussed using the modified NMR version of Benesi-Hildebrand equation and Graphpad Prism 6 package program.