Carbohydrate derived oligo(amidetriazoles) as anion binding receptors. NMR and MS analysis

FIDALGO, DANIELA M.; MONGE, MARIA E.; KOLENDER, ADRIANA A.; VARELA, O.

Nueva Orleans

Congreso; XXVIII International Carbohydrate Symposium; 2016

Preliminary modelling studies of high molecular weight poli(amide­triazoles), obtained in our laboratory, suggested stabilization of secondary structures by halide anions. This fact was attributed to the polarization of the C­H bond in 1,2,3­triazole ring, which allows the complexation of anions by hydrogen and halogen bonding. Therefore, oligo(amide­triazoles) 6 and 8, containing respectively two or three triazole units, were synthesized from D­glucono­1,5­lactone by microwave assisted Cu(I) catalyzed azide­alkyne cycloaddition. The interactions of 6 and 8 with halides were studied by NMR spectroscopy and direct infusion electrospray ionization single quadrupole mass spectrometry (DI­ESIMS).The 1H NMR spectra of 8, recorded in presence of Cl, Br or I, indicated that Cl­induced the most intense chemical shift displacement of the triazole protons. In order to determine the stoichiometry of the species formed, the method of continuous variation (Job?s plot) was applied to solutions containingcompounds 6 or 8 and different concentrations of Cl salts. Solutions containing 8, Cl, and Br salts were analyzed by DI­ESI­MS. The [M+Cl] adduct ion, which is typically observed in negative ion mode ESI, is only detected when 8 is mixed with Cl salts, suggesting that Cl complexation occurs in solution.Moreover, this adduct ion prevailed when the two anions were present, in agreement with 1H NMR results. The Job?s plots obtained by DI­ESI­MS and NMR spectroscopy suggested similar stoichiometry for the complexation of these oligomers with Cl, demonstrating the capability of these techniques tostudy complex ion binding and the potential use of the oligomers as ionophores.