Solvatochromaticity and pH dependence of the electronic absorption spectra of some purines and pyrimidines and their metal complexes

Masoud, Mamdouh S.; Shaker, Medhat A.; Ali, Alaa E.; Elasal, Gehan S.

doi:10.1016/j.saa.2011.03.029

Cited by 16 publications

(7 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The acidity constants of Methylene blue in this study are determined using three different spectrophotometric methods including the half- curve height, the modified limiting absorption and Colleter methods [ 47 ]. Table 6 , in the half-curve height method: the pKa values were evaluated at a constant wavelength from the half height of the A S versus pH curves, Fig.…”

Section: Resultsmentioning

confidence: 99%

The Shift in the Behavior of Methylene Blue Toward the Sensitivity of Medium: Solvatochromism, Solvent Parameters, Regression Analysis and Investigation of Cosolvent on the Acidity Constants

Hemdan

2023

J Fluoresc

View full text Add to dashboard Cite

The influence solvents from different polarity and hydrogen bonding ability on electronic absorption spectrum of Methylene blue was investigated. The visible absorption spectra were recorded in eleven neat solvents in the range 400–700 nm. Methylene blue has two absorption maxima, the first band assigned to n-π* from amino groups and the second band assigned to weakly forbidden n-π* transition with charge transfer. The charge transfer band of Methylene blue showed red shift with increasing the relative permittivity of neat solvents. The red shift in wavelength(λ max ) for the charge transfer band of Methylene blue was observed when proceeding from dioxane (λ max = 650 nm) into methanol (λ max = 655 nm) into cyclohexanone (λ max = 660 nm) into dimethylsulfoxide (λ max = 665 nm) as well as water (λ max = 665 nm), this shift not agree with the polarity of solvents but due to combination of several parameters. The absorption of charge transfer band in methanol and ethanol as hydrogen bonding donating solvents (HBD) showed the highest intensity than the absorption band in dimethylsulfoxide and dimethylformamide as hydrogen bonding accepting solvents (HBA) due to non-electrostatic interaction between the amino groups and solvents. The charge transfer band in neat solvents were correlated with several parameters using linear solvation energy relationships. The results showed that electrostatic interactions of the solvents play an important role in the shift of absorption maxima of Methylene blue in neat solvents. The acidity constants (pKa) of Methylene blue were estimated by using absorbance measurements in different media. The acidity constants (pKa) values of Methylene blue were affected by cosolvent, which the pKa values increasing in the order propanol < methanol < dioxane, this order not agreement with increasing the relative permittivity of the medium. Supplementary Information The online version contains supplementary material available at 10.1007/s10895-023-03234-y.

show abstract

Section: Resultsmentioning

confidence: 99%

The Shift in the Behavior of Methylene Blue Toward the Sensitivity of Medium: Solvatochromism, Solvent Parameters, Regression Analysis and Investigation of Cosolvent on the Acidity Constants

Hemdan

2023

J Fluoresc

View full text Add to dashboard Cite

show abstract

“…Red or blue spectral shifts can be indicated from the positive and negative signs of ∆ν, respectively [50,51]. All investigated compounds exhibited a positive absorption solvatochromism on increasing the solvent polarity (Table 16).…”

Section: Kamlet and Taft Methodsmentioning

confidence: 98%

Solvatochromic absorption and fluorescence studies of adenine, thymine and uracil thio-derived acyclonucleosides

et al. 2015

View full text Add to dashboard Cite

Adenine, thymine and uracil thio-derived acyclonucleosides were synthesized and characterized by UV-Vis, FT-IR, 1 H and 13 C NMR spectroscopic techniques. The photophysical properties of the derivatives were evaluated in solvents with diverse polarities and at various pH values. The solvent dependent absorbance and emission spectral shifts were analysed using physical parameters of the selected solvents. The regression and correlation coefficients were calculated using multiple regression techniques. The fitting coefficients gave an estimate of the contribution of each interaction to the total spectral shift in various solutions. Multiple linear regression studies, Kamlet-Taft equation and stokes shift correlation with orientation polarizability provide valuable information concerning spectroscopic characteristics of the studied molecules.

show abstract

“…Three different spectrophotometric methods are applied to calculate the pKa values. The half-curve height, the modified limiting absorption and Colleter methods [24].…”

Section: Calculation Of the Pka Values From Spectrophotometric Datamentioning

confidence: 99%

The Dependence of Acid-Base Equilbria and Acidity Constants of Congo Red in Buffer Solutions on the Ionic Strength

Hemdan

2024

JCTM

View full text Add to dashboard Cite

In this study, the spectrophotometric studies of aqueous ethanol solution of Congo red in various buffers solutions at room temperature 25oC and at different ionic strength of 0.05, 0.1, 0.3, and 0.5 KCl mol L-1 were investigated. The acidity constants of Congo red were estimated by three different methods. The two protonation stages were observed in pH range 2 - 4 and 4 - 6 as result as protonation of amino group and azo groups. The dependence of absorption spectra of Congo red on the ionic strength of solutions which exhibited blue shift with increases ionic strength in addition the shape and intensity were varied. Therefore, the acid-base equilibria shifted toward the higher pHs with the rise in ionic strength. Also, the acidity constants were affected by the ionic strength which the acidity constants decrease with increasing ionic strength of solution because the electrostatic interaction force increased.

show abstract

Solvatochromaticity and pH dependence of the electronic absorption spectra of some purines and pyrimidines and their metal complexes

Cited by 16 publications

References 42 publications

The Shift in the Behavior of Methylene Blue Toward the Sensitivity of Medium: Solvatochromism, Solvent Parameters, Regression Analysis and Investigation of Cosolvent on the Acidity Constants

The Shift in the Behavior of Methylene Blue Toward the Sensitivity of Medium: Solvatochromism, Solvent Parameters, Regression Analysis and Investigation of Cosolvent on the Acidity Constants

Solvatochromic absorption and fluorescence studies of adenine, thymine and uracil thio-derived acyclonucleosides

The Dependence of Acid-Base Equilbria and Acidity Constants of Congo Red in Buffer Solutions on the Ionic Strength

Contact Info

Product

Resources

About