Article

Diverse associations in the ternary systems of β-cyclodextrin, simple carbohydrates and phenyl derivatives of inorganic oxoacids

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Abstract

Complex formation reactions of phenylboronic, phenylphosphonic, phenylarsonic and 4-aminophenyl arsonic acids with β-cyclodextrin (cycloheptaamylose, β-CD) and some simple carbohydrates (mannitol, sorbitol, glucose) have been studied using spectrophotometric, potentiometric methods and solubility measurements, supplemented with HPLC and IR analyses of the solid samples. Equilibrium constants have been determined at ionic strength of 0.2M (NaCl) and 25°C. β-CD forms the most stable complexes with the neutral, undissociated forms of the acids, the stability constants are as follows: phenylboronic acid: 320 ± 36, phenylphosphonic acid: 108 ± 25, phenylarsonic acid: 97 ± 4 and 4-aminophenyl arsonic acid: 107 ± 10. The stability constants for the β-CD-complexes of the ionic forms are much lower. Ternary complexes of low stability could be detected in the case of phenylphosphonic acid and sorbitol with the undissociated form and with glucose and the dianion. In more concentrated solutions phenylboronic acid forms insoluble complexes with mannitol, sorbitol and β-CD. The solid phases obtained in the ternary systems are predominantly mixtures of ester type 3:1 complexes with the carbohydrate and 1:1 inclusion complex with the β-CD. No significant interaction has been found with glucose. The phenomena can be explained by the differences in the structures of the components and by the changes in the H-bonding network of β-CD on the complex formation.

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... The wide broads at about 3571-3200 cm -1 inFigure S1bwere assigned to the stretching vibrations of NH 2 /OH groups of guanosine molecules; and the brands at 1200-1000 cm -1 were the C-O stretching vibrations; 1000-700 cm -1 were the deformation vibrations of -OH groups. Significant changes were observed in these regions for the G-PyB/KCl xerogel (Figure S1c), proving the formation of ester-like C-O-B bonds.1,3,4 The amide vibration (ν (CO), δ (NH 2 )) of the guanosine molecules at 1734 cm -1 shifted toward a lower frequency at 1697 cm -1 for G-PyB xerogel, indicating the hydrogen bonding interactions between the guanosine amide of the G-PyB complex.5 ...
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