Formation of Host-Guest Complexes of β-Cyclodextrin and Perfluorooctanoic Acid

Abstract

Structural characterization and dynamic properties of solid-state inclusion complexes of β-cyclodextrin (β-CD) with perfluorooctanoic acid (PFOA) were investigated by (19)F/(13)C solid-state and (19)F/(1)H solution NMR spectroscopy. The complexes in the solid state were prepared using dissolution and slow cool methods, where thermal analyses (DSC and TGA), PXRD, and FT-IR results provided complementary support that inclusion complexes were formed between β-CD and PFOA with variable stoichiometry and inclusion geometry. (19)F DP (direct polarization) and (13)C CP (cross-polarization) with magic-angle spinning (MAS) solids NMR, along with (19)F/(1)H solution NMR were used to characterize the complexes in the solid and solution phases, respectively. The dynamics of the guest molecules in the inclusion complexes (ICs) were studied using variable temperature (VT) (19)F DP/MAS NMR experiments in the solid state. The guest molecules were observed to be in several different molecular environments, providing strong evidence of variable host-guest stoichiometry and inclusion geometry, in accordance with the preparation method of the complex and the conformational preference of PFOA. It was concluded from PXRD that β-CD and PFOA form inclusion complexes with "channel-type" structures. Variable spin rate (VSR) (19)F DP/MAS NMR was used to assess the phase purity of the complexes, and it was revealed that slow cooling resulted in relatively pure phases. In the solution state, (1)H and (19)F NMR complexation-induced chemical shifts (CISs) of β-CD and PFOA, respectively, provided strong support for the formation of 1:1 and 2:1 β-CD/PFOA inclusion complexes. The dynamics of the guest molecule in the β-CD/PFOA complexes in D(2)O solutions were probed using VT (19)F NMR and revealed some guest conformational and exchange dynamics as a function of temperature and the relative concentrations of the host and guest.

Fragmentation of Perfluorinated Membranes Used in Fuel Cells: Detecting Very Early Events by Selective Encapsulation of Short-Lived Fragments in β-Cyclodextrin

“…21 To the best of our knowledge no data have been published on complexes of PFOA adducts in the cyclodextrin host.…”

Photophysical Properties of 7‐(diethylamino)Coumarin‐3‐carboxylic Acid in the Nanocage of Cyclodextrins and in Different Solvents and Solvent Mixtures

“…and observed distinctly a different behavior of these dyes in these media *Corresponding author email: debabrata@iitp.ac.in (Debabrata Seth) compared to that observed in bulk media (10)(11)(12)(13)(14)(15)(16)(17). Several other workers studied different host-guest complexation using different kinds of probe molecules and using different methods (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37).…”

The Cyclodextrin-Perfluorinated Surfactant Host-Guest Complex: Fundamental Studies for Potential Environmental Remediation and Therapeutic Applications

“…As the ratio of CD increases, there are distinct changes in the chemical shifts and shape of the 19 F NMR peaks. Peak broadening is assigned to a more rigid structure of the guest when within the host (Karoyo et al 2011. Based on the results herein as well as the numerous previous studies, we focused on the β-CD:PFAS complexes (Guo et al 1992, Wilson and Verrall 1998a, Karoyo et al 2011.…”

“…Peak broadening is assigned to a more rigid structure of the guest when within the host (Karoyo et al 2011. Based on the results herein as well as the numerous previous studies, we focused on the β-CD:PFAS complexes (Guo et al 1992, Wilson and Verrall 1998a, Karoyo et al 2011. To probe the nature of the β-CD:PFOA complex, competition experiments were run using adamantane-carboxylic acid (Ada-COOH).…”

“…CDs have previously been show to exhibit host-guest interactions with perfluorocarboxylic acids (PFCAs) of various chain lengths (Palepu and Reinsborough 1989, Palepu and Richardson 1989, Guo et al 1992, Wilson and Verrall 1998a, Lima et al 2007, Karoyo et al 2011. Previously 19 F NMR spectroscopy has been used to study the change in chemical shifts of each fluorine peak on the PFAS backbone in order to calculate the strength of complexation (Guo et al 1992, Wilson and Verrall 1998a, Karoyo et al 2011). β-CD, the mid-sized CD, is the most promising for complexation of PFCAs, and exhibits both 1:1 and 2:1 complexes with PFCAs (Guo et al 1992, Wilson andVerrall 1998a…”