How does β-cyclodextrin affect the aggregation of sodium perfluoroheptanoate in aqueous solution: a 19F NMR study (original) (raw)
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How does β-cyclodextrin affect oxygen solubility in aqueous solutions of sodium perfluoroheptanoate?
Journal of Colloid and Interface Science, 2006
1 H and 19 F NMR spectra were recorded for D 2 O solutions of sodium perfluoroheptanoate with defined concentrations up to 200 mM, in the absence and presence of b-cyclodextrin (15 mM). Analysis of 1 H chemical shift data obtained by the method of continuous variations (Job's method) confirms the formation of 1:1 inclusion complexes for the perfluoroheptanote anion in b-cyclodextrin and leads to an estimate for the apparent inclusion constant ( ‡10 4 M -1 ). In addition, analysis of 19 F chemical shift data based on two simplifying assumptions (monodisperse perfluoroheptanoate solutions below the critical micellar concentration (CMC), and a single self-associated state after the CMC) enables to interpret all the experimental chemical shift data and allows to determine CMC values for the absence and presence of bcyclodextrin (104 and 116 mM). It is shown that the self-association of perfluoroheptanoate and its inclusion in b-cyclodextrin lead to shielding and deshielding of the fluorine atoms, respectively.
The Journal of Physical Chemistry C, 2015
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 1 H/ 19 F/ 13 C 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 13 C 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 1 H/ 19 F/ 13 C 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 CF 3 19 F NMR with MAS at 25 kHz and selected dipolar coupling strengths were utilized in conjunction with deconvolution analyses of the experimental CF 3 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 CF 3 group as well as rotations of the C−F bonds occur. 19 F 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.
The Journal of Physical Chemistry B, 2013
The structural characterization of solid-and solution-state inclusion complexes (ICs) of β-cyclodextrin (β-CD; host) with perfluorobutyric acid (PFBA; guest) is presented in this study. Complexes in the solid state were prepared at various host/guest mole ratios (i.e., 1:1 and 2:1) using a modified dissolution method. Thermal analyses and multinuclear 13 C NMR methods employing direct polarization (DP) and cross-polarization (CP) techniques with magic angle spinning (MAS) and high-power 1 H/ 19 F decoupling were used to characterize the solid-state host−guest complexes. Unequivocal evidence of the formation of β-CD/PFBA inclusion compounds was provided using 19 F → 13 C CP/MAS NMR results. Powder X-ray diffraction reveals that PFBA forms a "cage-type" structure with β-CD, in which the guest adopts gauche and near-linear conformations in the 1:1 and 2:1 complexes, respectively, according to Fourier transform infrared spectroscopy results. Interpretation of the NMR splitting patterns of PFBA spectrum in solution reveals that PFBA undergoes fast rotation of the CF 3 group on a 3-fold axis, while the remainder of the chain experiences a significant C−C bond rotation; hence, it is not locked in a particular rotamer configuration. The distribution of the rotational and axial motions in the β-CD/PFBA complexes in the solid state as revealed by NMR relaxation dynamic studies is a function of the host/guest mole ratios and is determined by the binding geometry of the guest.
1H NMR spectroscopy as a probe of intermolecular interactions in ?-cyclodextrin inclusion compounds
Journal of Inclusion Phenomena and Molecular Recognition in Chemistry, 1991
~H NMR spectroscopy was used to probe the formation of inclusion compounds of permethylated and peracetylated fl-cyclodextrins as host molecules and a variety of electronically very different guest molecules. Complexation, obtained only in water, was estimated quantitatively by means of chemical shift/concentration curves of relevant protons, and the intermolecular forces involved are criticially discussed.
NMR spectroscopy of inclusion complex of sodium diclofenac with β-cyclodextrin in aqueous solution
Biospectroscopy, 1997
The interaction between diclofenac (sodium salt of 2-[(2,6-dichlorophenyl)amino]benzeneacetic acid) and b-cyclodextrin in aqueous solution has been investigated by 1 H-NMR spectroscopic technique. The technique is based on the shielding of the b-cyclodextrin and drug protons. The spectra showed upfield shifts of the b-cyclodextrin protons in the presence of diclofenac, and the diclofenac protons also shifted upfield in the presence of b-cyclodextrin. The changes in chemical shifts of suitable guest-host protons are consistent with the formation of an inclusion complex diclofenac/ b-cyclodextrin. Presented in part at the European Conference of the Spec-is present in water, so it can be considered as a troscopy of Biomolecules, ECSBM'95, Villeneuve d'Ascq, 3-8 hydrophobic cavity. The inner cavity diameters of September 1995, France.
2010
The aggregation of perfluoroctanoate salts in H 2 O is studied by 19 F NMR on solutions of LiPFO, NaPFO, and CsPFO, without and with the addition of two poly(ethylene glycol) (PEG) oligomers of molecular weight 1500 and 3400 Da, respectively, and with the addition of suitable crown ethers. The 19 F chemical shift (cs) trends are monitored, at 25°C, in a concentration range including the critical micellar concentration (cmc) or, in the presence of PEG, the critical aggregation concentration (cac). The cac values in the samples with PEG are lower than the cmc values of the corresponding samples without PEG; moreover, the 19 F cs trends above the cac and above the polymer saturation concentration reveal and help to explain some peculiarities of the aggregation process of PEG on PFO micelles, which, in the first step, seems to occur while the surfactant concentration in water is still increasing. Also in LiPFO/H 2 O or NaPFO/H 2 O solutions containing 12-crown-4 or 15-crown-5 ethers, suitable to complex Li þ or Na þ ions, respectively, the cmc decreases. On the other hand, the micellization process in the presence of crown ethers does not show other peculiarities. The prevailing conformations of the PFO chain are discussed on the basis of quantum-mechanical calculations. The theoretical chemical shifts were computed at the DFT level of theory, taking into account the effects of the environment by means of the IEF-PCM method. The helical structure is the most stable one, but anti conformations are easily accessible, in both the aqueous and fluorinated environment. The comparison between computed and experimental chemical shifts indicates that anti conformations are more important in the micelles than in water and in CsPFO micelles than in LiPFO or NaPFO ones.
2005
methyl benzeneacetic acid hydrochloride, is a second generation antihistamine that is used to treat allergies. 1 It is a racemate and exists as zwitter ion in aqueous media at physiological pH. It belongs to the group of amine compounds bearing diphenylmethyl functionality. Like other members of this group, the drug is highly hydrophobic and slightly soluble in water. The study of inclusion complexes of cyclodextrins (CDs) is a subject of great interest. 2-4 CDs are oligosaccharides composed of six to eight glucopyranose units bound by α(1-4) linkages that are commonly named α-, β-, and γ-CD, respectively. β-CD, in particular, has an internal cavity shap-ed like a truncated cone. The interior of the cavity is relatively hydrophobic while the outer surface is quite hydrophilic because of the presence of numerous hydroxyl groups. CDs can accommodate a variety of guests into its cavity through non-covalent interactions. These complexes serve as models to mimic enzyme activity 5 and to ...
Formation of Host-Guest Complexes of β-Cyclodextrin and Perfluorooctanoic Acid
The Journal of Physical Chemistry B, 2011
Many fluorine-containing compounds such as pharmaceuticals, pesticides, coatings, adhesives, and surface-active agents represent a growing list of persistent organic pollutants (POPs) accumulating in Canadian and global environments. This is particularly true for recalcitrant perfluorinated compounds (PFCs) of the type CF 3-(CF 2) n-R 0 , where R 0 = CF 2 ÀOH, COOH, CONH 2 , or CF 2 ÀSO 3 H. There is a considerable interest in developing innovative green strategies that involve the sequestration of such PFCs with suitable sorbent materials that exhibit good sorption capacity and molecular selectivity. For example, Deng et al. developed a molecular imprinted polymer with good sorption toward perfluorooctane sulfonic acid (PFOS; R 0 = CF 2 ÀSO 3 H) in aqueous solution. 1 PFCs of the type described above possess unique physicochemical properties, as compared with their hydrocarbon analogues because they are generally apolar and relatively inert owing to the stability of the CÀF bond. 2 They generally have low vapor pressures (∼10 mmHg for PFOA; R 0 = CF 2 ÀCO 2 H at 25°C) 3 and exhibit long residence times in the environment. The relatively high surface activity of PFCs confers their application as highperformance surfactants, emulsifiers, and surface coatings for metals and paper. 3 PFOA and PFOS are commonly found in soil, sediments, and aquatic environments because of their ability to infiltrate groundwater to varying extents. Environmental contamination by PFCs was reported from direct discharge of industrial activities, for example, aqueous fire fighting foams 4 and wastewater effluents from water treatment plants. 5 Consumption of contaminated foods and inhalation of air laden with volatile PFCs (e.g., perfluorinated alcohols and esters) that may be degraded to PFOA are regarded as other possible ingestion pathways. 3,4 Despite the human health and environmental concerns of PFOA, the distribution pathways are not fully understood; however, researchers have linked its exposure to cancer, 6 birth defects, 7 infertility, 7 liver damage, 8 and suppression of immunity. 9À11 Therefore, there is a need to further study PFOA because of its widespread use and the
Langmuir, 2017
The aggregation of the most common natural cyclodextrins (α-, βand γ-) in aqueous 28 solutions is addressed by studying the CD-CD interactions using deuterium relaxation 29 rates for deuterium labelled CDs. Relaxation times (T 1) and its corresponding relaxation rates (R 1 =1/T 1) provide information about the rotational correlation times of CDs and 31 serve as a proxy for solute-solute interactions. Measured T 1 's for α-, β-, and γ-CD at the 32 lowest CD concentrations were in agreement with predictions of a hydrodynamic model 33 for toroids, in particular with regard to the dependence of T 1 on CD size. On the other 34 hand, the dependence of T 1 's with respect to the increase in CD concentration could not 35 be explained by hydrodynamic or direct interaction between CD molecules, and it is 36 suggested that there is an equilibrium between monomeric and dimeric CD to account 37 for the observed concentration dependence. No evidence in favor of large aggregates of 38 CD involving a non-negligible fraction was found for the investigated CDs.