The solvatochromic responses of six indicators namely Sudan orange, Alizarin yellow R, Aurin tricarboxylic acid, Alizarin yellow GG, Titan yellow and Eriochrome black-T, dissolved in seven solvents of different polarities, have been measured at room temperature. The UV/Vis absorption spectral shifts were analyzed by the multiple linear regression analysis and Kamlet-Taft equation. The observed solvatochromism was found to depend on the presence of the donor and acceptor substituents in the conjugated systems of the indicator and the physical properties of the solvent molecules. The pH effects on the wavenumbers of the absorption band maxima of some indicators with different constituents at room temperature were discussed and the mechanism of ionization was explained. The dissociation constants (pK a) of the investigated compounds were precisely assessed and the existence of the individual predominant ionic species was assigned by constructing distribution diagrams at different pH ranges.
The solvent impact can be decided by Solvent polarity scales, a solvatochromic parameter that has a distinctive position of UV-Visible absorption band within the extend between 250 and 700 nm. The spectral characteristics of Aniline Violet in several solvents at room temperature were analyzed which is that the point of considering the impact of solvents on the absorption spectra of this cationic dye in organic solvent of distinctive characters. The solvent impacts on the wavenumber of the absorption band maxima (max) were talked about utilizing the taking after solvent parameters, refractive index, n, relative permittivity, ε and therefore the empirical solvent polarity ET (30), (*, and ) and (SA, SB, SP and SPd). The solute–solvent interactions were decided on the premise of multilinear solvation energy relationships concept. The fitting coefficients gotten from this analysis allowed us to estimate the contribution of each type of interactions to the total spectral shifts in solution. The set up dependences between max and the solvent parameters emphasize that the visible band of the examined molecule is influenced by both non-specific and specific solute–solvent interactions. The results appeared the solvent polarizability has major impact on the spectral shift instead of hydrogen bonding accepting ability. Catalan strategy show higher acceptable correlation than Kamlet-Taft methodology and Katritzky methodology. The dissociation constant pKa and the isosbestic point of the explored compound were shown the presence of the individual predominate ionic species was assigned by constructing distribution charts at diverse pH ranges. The results showed that the relative permittivity constant, ε, is important factor affecting on the magnitude of the dissociation constant beside the hydrogen bonding of the solvent.
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.
Synthesis of new Fe(III), Co(II), Ni(II), and Cu(II) complexes of two azo ligands; 1-(phenyldiazenyl) naphthalene-2-ol (sudan orange R, HL1), and sodium 2-hydroxy-5-[(E)-(4-nitrophenyl) diazenyl]benzoate (alizarin yellow GG, HL2) have been reported. Stoichiometries of 1:2 and 1:3 (M:L) of the synthesized complexes were approved by total-reflection X-ray fluorescence technique (TXRF) and by elemental analyses. The geometry of complexes (octahedral and square planar) was typified by various spectroscopic, thermal, and magnetic techniques. The ESR spectroscopy showed that Cu(II) complexes are of different isotropic and rhombic symmetries with the existence of Cu–Cu ions interaction. TGA, DTA, and DSC analyses supported the multi-stage thermal decomposition mechanisms, where the thermal breakdown is ended by the formation of metal oxide in most cases. Moreover, chemical reactivity modeling using the density functional theory (DFT) method with the B3LYP/6–31 basis set, showed that metal complexes are more biologically active than their precursor ligands. The calculated lipophilicity character for metal complexes is in the range of 33.8–37.5 eV. Docking results revealed high scoring energy for [Fe(HL2)3].H2O complex and moderate inhibition strength of [Cu(L1)2].H2O complex versus 1bqb, 3t88, and 4esw proteins. Ultimately, the extent of biological effectiveness was endorsed experimentally against four microbial strains. The results are guidelines for toxicological investigations. Graphical Abstract
Synthesis of new Fe(III), Co(II), Ni(II), and Cu(II) complexes of two azo ligands; 1-(phenyldiazenyl) naphthalene-2-ol (sudan orange R, HL1), and sodium 2-hydroxy-5-[(E)-(4-nitrophenyl) diazenyl]benzoate (alizarin yellow GG, HL2) have been reported. Stoichiometries of 1:2 and 1:3 (M:L) of the synthesized complexes were approved by total-reflection X-ray fluorescence technique (TXRF) and by elemental analyses. Complexes geometry of octahedral and square planar types were characterized by various spectroscopic, thermal, and magnetic moment measurements. Notably, bidentate coordination was the common binding mode of the ligands under investigation. The ESR spectroscopy showed that Cu(II) complexes are of different isotropic and rhombic symmetries accompanied by the existence of Cu-Cu ions interaction. TGA, DTA and DSC techniques supported the multi-stage thermal decomposition mechanisms, where the thermal breakdown is ended by the formation of metal oxide in most cases. Moreover, optimization of the structure and chemical reactivity modeling using the density functional theory (DFT) method with the B3LYP/6–31 basis set, showed that metal complexes are more biologically active than their precursor ligands. The calculated lipophilicity character for metal complexes is in the range 33.8–37.5 eV. Furthermore, nucleophilic and electrophilic regions on the surface of the ligands have been mapped aiming to prove the preferable sites of interaction with the metal ions. Docking results revealed high scoring energy for [Fe(HL2)3].H2O complex and moderate inhibition strength of [Cu(L1)2].H2O complex versus 1bqb, 3t88 and 4esw proteins. Ultimately, the extent of biological effectiveness was endorsed experimentally against four microbial strains. The results are guidelines for toxicological investigations.
This work aimed to the study effect of ethanol ratios on the acidity constants of bromocresol purple. The acidity constants of BCP were determined in binary mixtures of water with ethanol containing 0, 30, 40, 50, 60, and 70% (v/v) using spectrophotometric methods. The results indicate the dependence of acidity constants on the ratio of ethanol. The values of logKa 1 and logKa 2 were correlated with the macroscopic (relative permittivity, ε) and microscopic Kamlet-Taft parameters (α, β, and π*) of binary mixtures. The in uence of solvent on the acidity constants was analyzed in terms of the KAT parameters in order to study the solvent-solute interaction. Multiple linear regression was used to nd the contribution of the microscopic parameters containing α (acidity), π* (dipolarity/polarizability), and β (basicity). It was found that α and β were the most predominant descriptors. Also, a relationship with reciprocal relative permittivity was obtained based on Born's model, showing the signi cance of speci c solute-solvent interactions. Therefore, the hydrogen bonding interactions between solute and solvent components are mainly responsible for the change in acidity constants of bromocresol purple of binary mixtures.
This work aimed to the study effect of ethanol ratios on the acidity constants of bromocresol purple. The acidity constants of BCP were determined in binary mixtures of water with ethanol containing 0, 30, 40, 50, 60, and 70% (v/v) using spectrophotometric methods. The results indicate the dependence of acidity constants on the ratio of ethanol. The values of logKa1 and logKa2 were correlated with the macroscopic (relative permittivity, ε) and microscopic Kamlet-Taft parameters (α, β, and π*) of binary mixtures. The influence of solvent on the acidity constants was analyzed in terms of the KAT parameters in order to study the solvent-solute interaction. Multiple linear regression was used to find the contribution of the microscopic parameters containing α (acidity), π* (dipolarity/polarizability), and β (basicity). It was found that α and β were the most predominant descriptors. Also, a relationship with reciprocal relative permittivity was obtained based on Born’s model, showing the significance of specific solute-solvent interactions. Therefore, the hydrogen bonding interactions between solute and solvent components are mainly responsible for the change in acidity constants of bromocresol purple of binary mixtures.
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