Visible and 13C nuclear magnetic resonance spectra of azo dyes and their complexes with cyclomalto-oligosaccharides

Suzuki, Miyoko; Takai, Hitoshi; Tanaka, Kiyo; Narita, Kozue; Fujiwara, Hideaki; Ohmori, Hidenobu

doi:10.1016/s0008-6215(96)90779-x

Cited by 12 publications

(12 citation statements)

References 6 publications

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“…Substitution on the CyD rims can greatly enhance the binding of many lipophilic host compounds. , NMR shifts, relaxation times, and 13 C NMR rotational correlation times support the idea that lengthening of the hydrophobic torus by substituting the CyD with methyl groups leads to increased interactions with the hydrophobic parts of substituted azo dyes . Permethylation seems to generate higher flexibility of α-CyD, thus allowing a NMR-evidenced inclusion of o -toluic acid .…”

Section: C7 Inclusion With Modified Cyclodextrinsc7a General Featuresmentioning

confidence: 77%

NMR Studies of Cyclodextrins and Cyclodextrin Complexes

et al. 1998

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Section: C7 Inclusion With Modified Cyclodextrinsc7a General Featuresmentioning

confidence: 77%

NMR Studies of Cyclodextrins and Cyclodextrin Complexes

et al. 1998

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“…16,19 Previous reports have suggested that a 1:2 complex, in which one MO is capped by two CD molecules at both ends ( In the case of -CD, it is implied that 1:1 complex was the main species even when the [CD]/[MO] ratio was rather large. 15 However, another absorption spectroscopic study shows the possibility that some degree of 1:2 complex can also be formed in higher concentration solution.…”

Section: Utl Signal Of Methyl Orange In Cyclodextrinsmentioning

confidence: 99%

Femtosecond Time-Resolved Spectroscopy of Photoisomerization of Methyl Orange in Cyclodextrins

et al. 2001

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The photoisomerization of methyl orange (MO) encapsulated in the cavities of R-, -, and γ-cyclodextrins (CDs) was measured by the ultrafast transient lens (UTL) method and transient absorption spectroscopy. The signal for free MO was well-fitted to the sum of two exponential functions, except for the component of the optical Kerr effect (OKE), and their time constants were j1 (τ 1 ) and ∼10 ps (τ 2 ). The UTL signal of the 1:1 complex, in which one MO molecule was included in one CD molecule, was almost the same as that of free MO. On the other hand, MO in two R-CD molecules showed slower relaxation and considerably lower yield of cis isomer. Thus, there were clear confinement effects when MO was capped at both ends by two CD molecules. The observed changes of ultrafast dynamics and yield of the isomer were explained in terms of CD-MO interactions and a steric effect. In the case of γ-CD, which included two MO molecules as a dimer, these confinement effects were also observed even when each MO was capped on only one side (2:1 complex). These results showed that a strong intermolecular interaction was induced between two MO molecules by confinement in a nanospace and this also hindered the isomerization. In particular, the complex with two γ-CD molecules (2:2 complex) showed significantly slower relaxation than the others, and no cis isomer was formed. It seemed that the intermolecular interaction of two MO molecules was further enhanced by photoexcitation in the 2:2 complex and this resulted in the formation of an aggregate-like intermediate in the γ-CD nanocavity.

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“…In addition to proteins and polyelectrolytes, dyes have also been employed as probes for the micropolarity of cyclodextrines, reverse micelles, microemulsions, liquid crystals, bilayers, and monolayers . The short-wavelength absorption band of MO has been reported in studies of monolayers and microemulsions 24 where MO was used as a solvatochromic reporter molecule.…”

Section: Introductionmentioning

confidence: 99%

Aggregation of Azo Dyes with Cationic Amphiphiles at Low Concentrations in Aqueous Solution

1999

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The aggregation of a series of n-alkyltrimethylammonium bromide (C n TAB, n = 10, 12, 14, 16, and 18) and 4-n-alkyl-1-methylpyridinium iodide amphiphiles (C m pyI, m = 8, 10, 12, and 14) induced by low concentrations of azo dyes in aqueous solution has been investigated by means of ultraviolet (UV) spectroscopy. It was observed that aggregation takes place at surfactant concentrations far below the cmc of C12TAB, C14TAB, C16TAB, and C18TAB with methyl orange (MO), ethyl orange (EO), and para-methyl red (pMR). Aggregation below the cmc of C10TAB was also induced by EO. In the case of MO and pMR, however, higher dye concentrations were necessary to induce aggregation. Interactions at low surfactant concentrations have also been observed in aqueous solutions of C10pyI, C12pyI, and C14pyI with MO. Binding of methyl red (MR), methyl yellow (MY), and azobenzene sulfonate (ABS) with cationic surfactants below their cmc did not occur. Aggregation was reflected by the appearance of a blue-shifted absorption band in the spectra of the dyes. Precipitates formed in aqueous solutions from the cationic surfactants and MO and pMR are C n TA−MO, C n TA−pMR, and C m py−MO salts and consist of an equimolar ratio of surfactant and dye. In similar experiments with EO, MR, MY, or ABS as the solvatochromic dye molecules, no precipitation occurred, although surfactant−EO salts precipitated at high EO concentration. Dye−surfactant salts formed from C n TAB and MO were found to form myelins in phase penetration experiments. Temperatures at which myelins start to form increase upon increasing alkyl chain length of the surfactant as revealed by optical microscopy. The formation of vesicles from C10TA−MO and from C12TA−MO crystals was indicated by electron microscopy. The presence and position of the ionic group in the dye molecule is important in determining the association. The importance of hydrophobic interactions is revealed by the chain length dependence on the aggregation process and the observation that interactions are absent in ethanol. Electrostatic interactions also play an important role, as shown by the effect of NaCl on the binding process.

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Visible and 13C nuclear magnetic resonance spectra of azo dyes and their complexes with cyclomalto-oligosaccharides

Cited by 12 publications

References 6 publications

NMR Studies of Cyclodextrins and Cyclodextrin Complexes

NMR Studies of Cyclodextrins and Cyclodextrin Complexes

Femtosecond Time-Resolved Spectroscopy of Photoisomerization of Methyl Orange in Cyclodextrins

Aggregation of Azo Dyes with Cationic Amphiphiles at Low Concentrations in Aqueous Solution

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