A nuclear magnetic resonance study of the solvatochromism of a pyridinium betaine

Dawber, J. Graham; Williams, Richard A.

doi:10.1039/f19868203097

Cited by 37 publications

(26 citation statements)

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“…Additional information can be obtained by correlating the regression coefficients of the TKA equation with the physicochemical properties of the probes, in particular their pK a in water, because of the importance to solvation of hydrogen-bonding to the phenolate oxygen of the probe [14]. This approach has been recently applied to the probes of Fig.…”

Section: Information From Solvatochromic Datamentioning

confidence: 99%

Understanding solvation

Seoud

2009

Pure and Applied Chemistry

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The effects of solvents on different chemical phenomena, including reactivity, spectroscopic data, and swelling of biopolymers can be rationalized by use of solvatochromic probes, substances whose UV-vis spectra, absorption, or emission are sensitive to the properties of the medium. Thermo-solvatochromism refers to the effect of temperature on solvatochromism. The study of both phenomena sheds light on the relative importance of the factors that contribute to solvation, namely, properties of the probe, those of the solvent (acidity, basicity, dipolarity/polarizability, and lipophilicity), and the temperature. Solvation in binary solvent mixtures is complex because of "preferential solvation" of the probe by some component of the mixture. A recently introduced solvent exchange model is based on the presence in the binary solvent mixture of the organic component (molecular solvent or ionic liquid), S, water, W, and a 1:1 hydrogen-bonded species (S-W). Solvation by the latter is more efficient than by its precursor solvents, due to probe-solvent hydrogen-bonding and hydrophobic interactions; dimethyl sulfoxide (DMSO)-W is an exception. Solvatochromic data are employed in order to explain apparently disconnected phenomena, namely, medium effect on the pH-independent hydrolysis of esters, 1 H NMR data of water-ionic liquid (IL) mixtures, and the swelling of cellulose.

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Section: Information From Solvatochromic Datamentioning

confidence: 99%

Understanding solvation

Seoud

2009

Pure and Applied Chemistry

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“…Additionally, all j IL-W/W are larger than the corresponding j IL-W/IL indicating, in agreement with the small values of j W/IL , that IL-W is more efficient in displacing water than IL from the probe solvation shell. Whereas water solvates the probe by a single mechanism (hydrogen-bonding to the phenolate oxygen); 28 hydrogenbonding, dipole-dipole, and solvophobic interactions are operative for both IL and IL-W.…”

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“…It is plausible that the IL solvates the probe by a combination of hydrogen-bonding, especially that between the relatively acidic C2-H of the imidazolium ring and the probe phenolate oxygen; 28,29 the Cl À and the probe positively charged nitrogen, as well as solvophobic interactions, vide infra.…”

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confidence: 99%

Solvation in aqueous binary mixtures: consequences of the hydrophobic character of the ionic liquids and the solvatochromic probes

2012

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2012Solvation in aqueous binary mixtures:consequences of the hydrophobic character of the ionic liquids and the solvatochromic probes NEW JOURNAL OF CHEMISTRY, CAMBRIDGE, v. 36, n. 11, pp. 2353-2360, NOV, 2012 Information on the solvation in mixtures of water, W, and the ionic liquids, ILs, 1-allyl-3-R-imidazolium chlorides; R = methyl, 1-butyl, and 1-hexyl, has been obtained from the responses of the following solvatochromic probes: 2,6-dibromo-4-[(E)-2-(1-R-pyridinium-4-yl)ethenyl] phenolate, R = methyl, MePMBr 2 ; 1-octyl, OcPMBr 2 , and the corresponding quinolinium derivative, MeQMBr 2 . A model developed for solvation in binary mixtures of W and molecular solvents has been extended to the present mixtures. Our objective is to assess the relevance to solvation of hydrogen-bonding and the hydrophobic character of the IL and the solvatochromic probe. Plots of the medium empirical polarity, E T (probe) versus its composition revealed non-ideal behavior, attributed to preferential solvation by the IL and, more efficiently, by the IL-W hydrogen-bonded complex. The deviation from linearity increases as a function of increasing number of carbon atoms in the alkyl group of the IL, and is larger than that observed for solvation by W plus molecular solvents (1-propanol and 2-(1-butoxy)ethanol) that are more hydrophobic than the ILs investigated. This enhanced deviation is attributed to the more organized structure of the ILs proper, which persists in their aqueous solutions. MeQMBr 2 is more susceptible to solvent lipophilicity than OcPMBr 2 , although the former probe is less lipophilic. This enhanced susceptibility agrees with the important effect of annelation on the contributions of the quinonoid and zwitterionic limiting structures to the ground and excited states of the probe, hence on its response to both medium composition and lipophilicity of the IL.

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“…solution of Brooker's merocyanine or Reichardt's dye imparts a hypsochromic shift in l max due to the formation of H-bonds between the O À donor moiety in the dye and the eOH group of the added compound [11,17]. In this context, a 1:1 DMSO:water solution of DIC is blue coloured and it was expected that the addition of the water-soluble calix [4]arene-p-sulfonate (1) would lower the absorbance of the dye at l max (625 nm), changing the colour of the dye solution as a result of the formation of the H-bonded DIC:calix [4]arene-p-sulfonate complex (3).…”

Section: Resultsmentioning

confidence: 99%