Medium Effect on the Ionisation Constants of Some Hydroxy Derivatives of 1-Ethyl-2-styrylpyridinium and -quinolinium Iodides

Mahmoud, M. R.; Abd-Elhamide, R.; Idriss, K. A.

doi:10.1246/bcsj.52.574

Cited by 9 publications

(14 citation statements)

References 7 publications

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“…Similar results were obtained by Mahmoud et al, 14,18 who attributed the presence of one visible band at low pH to a species with a non-ionized OH-group and the second at high pH to a species with a deprotonated OH group. We attributed the benzenoid structure to the protonated form of EPC.…”

Section: Absorption Spectra Of Epc At Different Phsupporting

confidence: 88%

“…Other authors reported the pK a values of some hydroxy derivatives of 1-ethyl-2-styrylpyridinium and quinolinium iodides, 14 measured in mixtures of organic solvents and water. They found that pK a values of hydroxystilbazolium salts decrease with increasing fraction of the organic solvent, depending also on solvent polarity and its ability to form hydrogenbonded complexes.…”

Section: Introductionmentioning

confidence: 99%

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Influence of pH on photophysical properties of (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride

Prukała

Gierszewski

et al. 2012

Photochem Photobiol Sci

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The protonation/deprotonation equilibrium was investigated for N-p-chlorobenzyl-substituted (E)-4'-hydroxy stilbazolium halide, namely (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride (EPC). Absorption, emission and synchronous scanning spectra were used to explain the observed phenomena. The excited state lifetimes of the protonated and deprotonated forms of EPC were measured and discussed. Absorption spectra were used to determine its pK(a) value in the ground state. We conclude that the protonation/deprotonation equilibrium is not attained in the first excited state of EPC, for kinetic reasons. The quinoid and benzenoid structures of EPC in the ground and excited state are discussed in acidic and basic range of pH. Aqueous solutions of EPC were yellow at pH < 7 and red at pH > 7, and addition of alcohols (methanol or 2-propanol) enhanced this change. Therefore, quaternary stilbazolium salts were investigated for application as acid-base indicators.

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Section: Absorption Spectra Of Epc At Different Phsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Influence of pH on photophysical properties of (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride

Prukała

Gierszewski

et al. 2012

Photochem Photobiol Sci

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“…Furthermore, the variation of the measured acidity constants in solutions containing the same mole percentage of the applied organic solvents may be explained considering the following facts: i) Acetonitrile, acetone, dioxane, DMF and DMSO have a lower tendency to develop hydrogen bonds to the conjugate base B -than alcohol, 26 26,28,31 ii) Acetonitrile, acetone and dioxane are also considered to be poorer hydrogen bond acceptors compared to water. 29−32 Thus, the free conjugate base B − and the proton H + are lowing stabilized by hydrogen bonding interactions in aqueous mixtures of these solvents affording high pK a values.…”

Section: Resultsmentioning

confidence: 99%

“…26,27 Accordingly, one can expect a higher stabilization of the conjugate base B − of each compound by the dispersion forces, arise from the induced dipole-dipole interactions, established between the delocalized oscillator dipole of the conjugate base and the localized oscillator dipole of solvent molecules. Furthermore, the free energy change of proton transfer (∆G t(H + ) ) from pure water to organic-solvent mixtures studied are all negative indicating a highly stabilization of proton in aqueous-organic solvent mixtures as compared to a pure aqueous medium.…”

Section: Resultsmentioning

confidence: 99%

The Acidity Constants of Some Pyrimidine Bases in Various Water Organic Solvent Media

2004

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The acid ionization constants of some pyrimidine bases of nucleic acids were determined pH-metrically at 25 degrees C and at the constant ionic strength I = 0.10 mol l(-1) (KNO3) in pure water as well as in aqueous media containing variable mole percentages (5-30%) of organic solvents. The organic solvents used were methanol, ethanol, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetonitrile, acetone and dioxane. The results obtained indicated that the acidity constants are generally decreased as the content of an organic solvent in the medium is increased. It was deduced that the hydrogen bonding interactions and the solvent basicity in addition to the electrostatic effect are the major effects influencing significantly the acid ionization process of pyrimidine bases in the different water-organic solvent media. Some thermodynamic parameters (deltaH, deltaG degrees, deltaS degrees) of the ionization process over the temperature range 5-45 degrees C in pure water were also determined and discussed.

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“…Unlike cyanine dye related 4-hydroxystyryl dyes, which may deprotonate to the corresponding merocyanine form (accompanied almost by an bathochromic shift of spectral properties; pK in the order of magnitude 8. 0-8.8 (AbdelMottaleb and Sherief 1984;Mahmoud et al 1979;Schulte-Frohlinde and Güsten 1971), novel dialkylarylaminostyryl substrates can be protonated to corresponding quaternary ammonium salts (pK about 0.5-2, Kormosh et al 2002). In addition (and not shown), in the case of all substrate variants discussed here, under strong basic conditions nucleophilic OH -attack on the positively charged p-system may occur, resulting in strong hypsochromic shifts or decolorization (pK about 10-13.6, Kormosh et al 2002).…”

Section: Synthesismentioning

confidence: 99%

N,N-Dialkylaminostyryl dyes: specific and highly fluorescent substrates of peroxidase and their application in histochemistry

et al. 2007

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Fluorescent labeling of immuno-bound or endogenous peroxidase (PO) activity has been achieved to date by means of phenol derivatives with a low substitution degree. Here it is demonstrated that N,N-dialkylamino-styryl dyes can also act as fluorescent substrates of PO. They undergo enzymatically cross-linking reactions to surrounding cell constituents in an analogous manner thus permitting highly fluorescent and permanent labeling. This approach is narrowly related to the catalyzed reporter deposition (CARD) technique based on tyramine conjugates and the recently described catalytic cross-linking approach of hydroxystyryl derivatives. The substitution patterns for optimal cross-linking capability and the spectral properties of obtained specific reaction products were studied using an iterative semi-empirical approach. The best staining performance is achieved with N,N-dimethylaminoaryl derivatives. Their N,N-dialkyl homologues as well as the primary aryl amine pendants failed as PO substrates. Due to their basic character, novel substrates occasionally tend to unspecific interactions (staining nuclei, mast cells, or keratin). Centering this side specificity and repressing the staining capability of PO was achieved by chemical modification of the respective dye leading to new specific probes for keratin and cytoplasmatic RNA. In conclusion, catalytic cross-linking of heterocyclic 4-N,N-dimethylamino-styryl dyes represents a promising approach for the permanent fluorescent staining of PO in fixed cells and tissues, complementing the CARD technique. In contrast to CARD-related approaches, new substrates are characterized by a broad excitation and emission range of fluorescence and the outstanding spatial resolution of specific fluorescence signaling known so far from their 4-hydroxystyryl analogues. They currently represent the smallest fluorescent substrates of PO. Histochemical and immuno-histochemical applications share several outstanding features: High detection sensitivity, spatial resolution of fluorescence signaling, and photo stability. 4-N,N-dimethylamino-styryl substrates are compatible with their phenol and phenol-ester analogues. Their combination facilitates the trichromatic immuno-histochemical demonstration of three different targets simultaneously at one excitation wavelength in a conventional epi-fluorescence microscope.

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Medium Effect on the Ionisation Constants of Some Hydroxy Derivatives of 1-Ethyl-2-styrylpyridinium and -quinolinium Iodides

Cited by 9 publications

References 7 publications

Influence of pH on photophysical properties of (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride

Influence of pH on photophysical properties of (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride

The Acidity Constants of Some Pyrimidine Bases in Various Water Organic Solvent Media

N,N-Dialkylaminostyryl dyes: specific and highly fluorescent substrates of peroxidase and their application in histochemistry

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