High-resolution solid-state 13C NMR study of per(3,6-anhydro)-α-cyclodextrin based polymers and of their chromium complexes

High-resolution solid-state 13C NMR was employed to characterise polymers made of per-3,6-anhydro-α-cyclodextrins with 1,6-diisocyanato-hexan used to bridge the macrocyles. These materials were designed because of their insolubility and their extractant properties due to the presence of the cyclodextrin rings. The properties of this new type of material appear very promising as potential extractant of different oxoanions. The properties of these materials to bind chromate or dichromate ions appear to be particularly attractive since the extraction of chromium is high and moreover there is no degradation of the polymers that can be further regenerated. These features rely mostly on qualitative and quantitative analyses of CP/MAS spectra. The studies of the NMR relaxation times, TCH, T1pH and T1C for the starting polymers and its metal complexes allowed obtaining valuable insights concerning the molecular sites of interactions of the polymers with the oxoanions.