Interaction of β-cyclodextrin with mercury(II) nitrate

Abstract

546.492+547.458.68The interaction of β-cyclodextrin with mercury(II) nitrate has been studied using UV, IR, and 1 H NMR spectroscopy, elemental analysis, and quantitative chemical analysis. The optimum conditions for complex formation were established. The stability constant of the 1:1 inclusion complex of β-cyclodextrin and nitrate was calculated. The formation of supermolecules of composition C 42 H 70 O 35 ⋅3Hg(NO 3 ) 2 in solution and on a silica surface chemically modified with β-cyclodextrin was shown.Introduction. Cyclodextrins are cyclic oligomers of α-D-glucose. They are widely used to increase the solubility and stability of medicinal and biologically active compounds and for chromatographic separation of mixtures of organic compounds because of their unique ability to form inclusion complexes with many organic molecules [1][2][3][4][5]. The application of cyclodextrins for the extraction, concentration, and analysis of toxic metals in environmental samples is promising. This may explain the vigorously developing research on the preparation of water-insoluble cyclodextrins [6] and their attachment to the surface of inorganic matrices [7-9]. β-Cyclodextrin was previously immobilized chemically on the surface of amorphous wide-pore silica [10][11][12]. The β-cyclodextrin-containing silica exhibited a high affinity for Hg(II) ions. Adsorption equilibrium is attained after only 15 min. The Hg(II) binding constant increases by two orders of magnitude compared with hydroxylated silica. Herein the interaction of β-cyclodextrin with mercury(II) nitrate in aqueous solution is studied in order to find the reasons for the high affinity of β-cyclodextrin-containing silica for Hg(II).Experimental. β-Cyclodextrin (Fluka, 99%) and Hg(NO 3 ) 2 (Khimlaborreaktiv, analytically pure) were used without further purification. UV absorption spectra of Hg(NO 3 ) 2 solutions were recorded on a Specord M-40 spectrophotometer in the wavelength range 260-400 nm in quartz cuvettes (l = 1 cm). The percent content of the various Hg(II) species in solution at pH 1-5 was calculated using the program Chemical Equilibria in AQuatic System. Elemental analyses were performed on an Elemental Analyzer EA 1110. IR spectra of powders were recorded on a Thermo Nicolet NEXUS single-beam Fourier IR spectrophotometer in the frequency range 4000-400 cm -1 . IR spectra were recorded using pressed disks of ~30 mg mass with pressing pressure 10 8 Pa. 1 H NMR spectra were measured at T = 25 o C in DMSO-d 6 on a Varian-VXR-300 (300 mHz) spectrometer with TMS internal standard. The Hg(II) content was determined using back titration with trilon [13].Results and Discussion. A symmetric absorption band with λ max = 302 nm and ε = 300 L/mol⋅cm ( Fig. 1) that belongs to the n → π * -transition of the N=O chromophore in the nitrate ion was recorded in the electronic spectrum of aqueous Hg(NO 3 ) 2 (0.001 M) [14]. Upon addition to the Hg(NO 3 ) 2 solution of given amounts of β-cyclodextrin, which has no characteristic absorption bands in the UV region, the abso...

Synthesis, characterization and sorption properties of silica modified with some derivatives of β-cyclodextrin

“…1, curve 2) [50,51]. These data are consistent with the 1 H NMR results [52]. For modified ␤-cyclodextrin the protons' signals of toluenesulfonyl group with chemical shifts ı (ppm) were registered: 2.433 (s) assigned to methyl radical of the toluenesulfonyl group, and also the signals at 7.452 (d) and 7.747 (d) attributed to protons of the benzene ring at the positions 3, 5 and 2, 6 respectively ( Fig.…”

“…It was found that inner cavities of ␤-cyclodextrin molecules are occupied by nitrate-ions [52] and therefore they cannot absorb metal cations. Residual surface aminopropyl groups and functional groups of narrow edge of grafted cyclic oligosaccharides molecules are sorption inactive.…”

Self-assembly of Ag nanoparticles using hydroxypropyl cyclodextrin: synthesis, characterisation and application for the catalytic reduction of p-nitrophenol

“…The formation of inclusion complex between b-CD and Hg(II) has been reported earlier. 65 Such a host-guest interaction assists assembly of b-HPCD-AgNPs when Hg is introduced into the system, which is similar to that of the AuNP assembly formed by a b-CD and osmium complex. 66 Such aggregation-enhanced emission phenomenon has been reported previously.…”

Nanosized centers for mercury(II) ions adsorption on a surface of modified silica

“…5. Predominant forms of mercury(II) in a weakly acidic range are Hg 2+ and Hg(OH) + [42]. The uptake of mercury(II) for adsorbents 1 and 2 is negligible.…”