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Solvent effect on the spectral properties of Neutral Red.

Rauf MA, Soliman AA, Khattab M - Chem Cent J (2008)

Bottom Line: This showed that the unified scale for estimating the solvent effect on the absorption of the Neutral Red dye is more adopted and more applicable than the pi* scale model.The unified scale for estimating the solvent effect on the absorption of Neutral Red dye is more adopted and more applicable than the pi* scale model.This may be due to complications from both pi-pi* charge transfer interactions and incomplete complexation of the solute; these effects are averaged out in the derived beta and pi parameters and thus limit their applicability.

View Article: PubMed Central - HTML - PubMed

Affiliation: Chemistry Department, UAE University, Al-Ain, UAE. raufmapk@yahoo.com

ABSTRACT

Background: The study was aimed at investigating the effect of various solvents on the absorption spectra of Neutral Red, a dye belonging to the quinone-imine class of dyes. The solvents chosen for the study were water, ethanol, acetonitrile, acetone, propan-1-ol, chloroform, nitrobenzene, ethyleneglycol, acetic acid, DMSO and DMF.

Results: The results have shown that the absorption maxima of dyes are dependent on solvent polarity. In non-hydrogen-bond donating solvents, solvation of dye molecules probably occurs via dipole-dipole interactions, whereas in hydrogen-bond donating solvents the phenomenon is more hydrogen bonding in nature. To estimate the contribution of the different variables on the wave number of the Neutral Red dye, regression analyses using the ECW model were compared with the pi* scale model. This showed that the unified scale for estimating the solvent effect on the absorption of the Neutral Red dye is more adopted and more applicable than the pi* scale model.

Conclusion: Absorption maxima of dyes are dependent on solvent polarity. Solvation of dye molecules probably occurs via dipole-dipole interactions in non-hydrogen-bond donating solvents, whereas in hydrogen-bond donating solvents the phenomenon is more hydrogen bonding in nature. The unified scale for estimating the solvent effect on the absorption of Neutral Red dye is more adopted and more applicable than the pi* scale model. This may be due to complications from both pi-pi* charge transfer interactions and incomplete complexation of the solute; these effects are averaged out in the derived beta and pi parameters and thus limit their applicability.

No MeSH data available.


Related in: MedlinePlus

Absorption shift of dye solution as a function of solvent polarizability (π*).
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Figure 3: Absorption shift of dye solution as a function of solvent polarizability (π*).

Mentions: A plot of λmax versus the dielectric constant values in various non-HBD and HBD solvents is shown in figure 2A and 2B. It can be seen from this figure that with increasing dielectric constant values, the spectrum is shifted to higher wavelength. The spectral changes observed in water were quite distinct from those in other solvents. The λmax of dye solution in water was found at lower wavelengths as compared to in other solvents although its dielectric constant is the highest among these solvents. This might be due to the formation of strong hydrogen bond between dye and water molecule. Thus different phenomena are present in various media. An increase in λmax values with π* (dipolarity/polarizability) as shown in figure 3 also indicates that dye interaction becomes different with increasing capability of a given solvent to form H bonds in solution.


Solvent effect on the spectral properties of Neutral Red.

Rauf MA, Soliman AA, Khattab M - Chem Cent J (2008)

Absorption shift of dye solution as a function of solvent polarizability (π*).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2571090&req=5

Figure 3: Absorption shift of dye solution as a function of solvent polarizability (π*).
Mentions: A plot of λmax versus the dielectric constant values in various non-HBD and HBD solvents is shown in figure 2A and 2B. It can be seen from this figure that with increasing dielectric constant values, the spectrum is shifted to higher wavelength. The spectral changes observed in water were quite distinct from those in other solvents. The λmax of dye solution in water was found at lower wavelengths as compared to in other solvents although its dielectric constant is the highest among these solvents. This might be due to the formation of strong hydrogen bond between dye and water molecule. Thus different phenomena are present in various media. An increase in λmax values with π* (dipolarity/polarizability) as shown in figure 3 also indicates that dye interaction becomes different with increasing capability of a given solvent to form H bonds in solution.

Bottom Line: This showed that the unified scale for estimating the solvent effect on the absorption of the Neutral Red dye is more adopted and more applicable than the pi* scale model.The unified scale for estimating the solvent effect on the absorption of Neutral Red dye is more adopted and more applicable than the pi* scale model.This may be due to complications from both pi-pi* charge transfer interactions and incomplete complexation of the solute; these effects are averaged out in the derived beta and pi parameters and thus limit their applicability.

View Article: PubMed Central - HTML - PubMed

Affiliation: Chemistry Department, UAE University, Al-Ain, UAE. raufmapk@yahoo.com

ABSTRACT

Background: The study was aimed at investigating the effect of various solvents on the absorption spectra of Neutral Red, a dye belonging to the quinone-imine class of dyes. The solvents chosen for the study were water, ethanol, acetonitrile, acetone, propan-1-ol, chloroform, nitrobenzene, ethyleneglycol, acetic acid, DMSO and DMF.

Results: The results have shown that the absorption maxima of dyes are dependent on solvent polarity. In non-hydrogen-bond donating solvents, solvation of dye molecules probably occurs via dipole-dipole interactions, whereas in hydrogen-bond donating solvents the phenomenon is more hydrogen bonding in nature. To estimate the contribution of the different variables on the wave number of the Neutral Red dye, regression analyses using the ECW model were compared with the pi* scale model. This showed that the unified scale for estimating the solvent effect on the absorption of the Neutral Red dye is more adopted and more applicable than the pi* scale model.

Conclusion: Absorption maxima of dyes are dependent on solvent polarity. Solvation of dye molecules probably occurs via dipole-dipole interactions in non-hydrogen-bond donating solvents, whereas in hydrogen-bond donating solvents the phenomenon is more hydrogen bonding in nature. The unified scale for estimating the solvent effect on the absorption of Neutral Red dye is more adopted and more applicable than the pi* scale model. This may be due to complications from both pi-pi* charge transfer interactions and incomplete complexation of the solute; these effects are averaged out in the derived beta and pi parameters and thus limit their applicability.

No MeSH data available.


Related in: MedlinePlus