Counterion Anchoring Effect on the Structure of the Solid-State Inclusion Complexes of β-Cyclodextrin and Sodium Perfluorooctanoate

Abstract

Characterization of the structure and dynamics for the solid inclusion complexes (ICs) between β-cyclodextrin (β-CD; host) and sodium perfluorooctanoate (SPFO; guest) was carried out using 1H/19F/13C NMR spectroscopy. The 1:1 and 2:1 β-CD/SPFO solid complexes were prepared by a modified dissolution method. Evidence for the formation of β-CD/SPFO ICs was provided by 13C DP (direct polarization) and CP (cross-polarization) solid-state NMR spectroscopy with magic angle spinning (MAS) at 20 kHz. The complexation-induced shifts (CIS) of 1H/19F/13C nuclei between solution and the solid state for β-CD/SPFO complexes and the closely related complexes of β-CD/PFOA (perfluorooctanoic acid) were compared. The counterion effect for SPFO and PFOA was observed according to their variable structure and binding as inclusion compounds with β-CD. The effect of sodium versus hydronium counterions on the structure and dynamics of inclusion complexes for these systems was supported by DSC, TGA, FT-IR, and powder X-ray diffraction (PXRD). Simulations of the CF3 19F NMR with MAS at 25 kHz and selected dipolar coupling strengths were utilized in conjunction with deconvolution analyses of the experimental CF3 lineshapes to probe the dynamic properties of SPFO and its complexes with β-CD. The dynamics of the guest are influenced by the host/guest binding geometry and the stoichiometry of the complex, where free rotation of the CF3 group as well as rotations of the C–F bonds occur. 19F DP/MAS NMR results and spin–lattice (T 1) and spin–spin (T 2) relaxation times in the laboratory frame at variable temperatures in the solid phase indicate that the dynamics of SPFO in β-CD/SPFO complexes are unique compared to those of PFOA in β-CD/PFOA complexes, due to the role of counterion effects of the guest.

Modular Chitosan-Based Adsorbents for Tunable Uptake of Sulfate from Water

“…This trend corresponds to the level of glutaraldehyde cross-linking, where a stoichiometric excess of glutaraldehyde is required for effective cross-linking at these conditions. Also, the spectral intensity of the N=C-groups in the bead are influenced by the presence of Ca 2+ due to the role of chelation on the cross-polarization dynamics of the system [ 50 ]. Aside from the NMR spectral confirmation of the products reported in Figure 2 , there is a need to characterize the thermal stability of the biopolymer network since thermal analysis was reported to be sensitive to be sensitive toward the structure and bonding variability of the chitosan composites, as described elsewhere [ 51 ].…”

β-Cyclodextrin Attenuates Perfluorooctanoic Acid Toxicity in the Zebrafish Embryo Model

“…They are inexpensive, water soluble, and non-toxic, and have been used not only in environmental remediation applications, but also as drug delivery systems for hydrophobic drugs [ 14 , 15 , 16 , 17 ]. β-Cyclodextrin (β-CD), made up of seven glucose monomers, has been shown to strongly encapsulate PFOA to form one of the strongest known CD-based host–guest complexes [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. The fully fluorinated backbone of the PFOA alkyl chain interacts with the hydrophobic β-CD cavity via van der Waals interactions, while the PFOA carboxylate group can form hydrogen bonds with hydroxyl groups lining the cavity perimeter of β-CD ( Figure 1 ).…”

Cu (II)-β-CD as Water-Loving Catalyst for One-Pot Synthesis of Triazoles and Biofuels Intermediate at Room Temperature without Any Other Additive

“…Due to structural arrangement of β‐CD, they are effective for various organic synthesis for example, Michael addition, Suzuki coupling and Heck reaction . Other than organic synthesis, CD provides surface for binds various metals by host‐guest interaction . Kang et al.…”