Solvent and substituent effects on spectroscopical changes of some diazoaminobenzene derivatives

Development a spectrofluorometric micellar supported encapsulated method for micro determination of silver ion using new 2,6-disubstituted pyridine derivatives

Herein, the presented manuscript provides for an extensive spectrofluorimetric method for micro determination of silver ion. This established method based on the use of the three synthesized 2,6-disubstituted pyridine derivatives (R1, R2 and R3) through exploiting their high fluorescence emission property. A noticeable effect on the fluorescence emission of the reagents after chelation with Ag (I) was monitored. Its noteworthy that the sensitivity and stability of this method was increased by using micellar medium. After chelation with Ag(I), the fluorescence emission of the ligands R1 and R2 were effectively quenched in a regular manner by increasing Ag(I) concentration. In contrast, an increase of the fluorescence intensity for reagent R3 after addition of Ag (I) was observed. The solvatochromism for all reagents under investigation was examined in different solvent. Furthermore, the chelation between Ag(I) and the and designed pyridine reagents was assessed spectrophotometrically. The optimum conditions for the most stable complexes which give a high signal difference were explored and well-determined. The linear range for determination of silver ion were determined and found to be 0.18-1.16, 0.06-0.59 and 0.18-1.43 μg mL^-1 for R1, R2 and R3, respectively. The statistical analytical parameters such as LOD, LOQ, SD of slope, SD of intercept and RDS were calculated. In addition, the developed methods were efficaciously applied for determination of Ag(I) in some water samples. These selective complexation methods found to be in good precision compared to official and reported method as revealed F-test.

The crystal structure of (E)-1-(4-methoxyphenyl)-3-(2-nitrophenyl)triaz-1-ene C8H8N2O4

C8H8N2O4, monoclinic, C2/c (no. 15) , a = 27.748(5) Å, b = 5.6488(10) Å, c = 16.437(3) Å, β = 93.393(3)°, V = 2571.87 Å3, Z = 8, R gt(F) = 0.0330, wR ref(F 2) = 0.0963, T = 296(2) K.

Understanding the crystalline formation of triazene N-oxides and the role of halogen⋯π interactions

Normalized parameters are presented to assist the interpretation of crystal mechanisms of a series of triazene N1-oxides. The role of halogen⋯π interactions is discussed.

Photophysical properties of porphyrin derivatives: Influence of the alkyl chains in homogeneous and micro-heterogeneous systems

This work is focused on the evaluation of the photophysical properties of protoporphyrin-IX derivatives with different alkyl chains. The goal of this work is to understand the physicochemical properties and select prototypes of photosensitizers for photodynamic therapy. Solvents with different dielectric constants were used to obtain relevant data on different physical and chemical processes, such as fluorescence quantum yield and emission level of aggregation in nonpolar media. In addition, studies were conducted in micro-heterogeneous systems through the interaction of porphyrin derivatives with different surfactants, such as cetyltrimethylammonium bromide, sodium dodecyl sulfate and octyl phenol ethoxylate. The compounds were characterized by electronic absorption spectroscopy in the ultraviolet-visible region and fluorescence emission spectroscopy. The comparative study between the different chemical environments evaluated in the present study represents a relevant contribution to the comprehension of the properties acquired by the porphyrins in different micro-heterogeneous systems, which allows us to understand various interactions that these compounds are subject in biological medium, such as the influence of the polarity of the medium in the reactivity of porphyrins with nonpolar substituents. These results show the decisive physicochemical influence of the alkyl chains on the properties of the tetraazomacrocycle porphyrin.

Solvation and equilibrium studies of some compounds containing azo and nitroso chromophores

The stability studies of biologically active phenylazo-dinitroso resorsinol and o-hydroxy phenyl azo-dinitroso resorsinol compounds were studied. The dissociation constants and the thermodynamic parameters of dissociation were evaluated and determined potentiometrically. Regression analysis is applied for correlating the different parameters by using the SPSS program. The results help to assign the solute-solvent interactions and the solvatochromic potential of the investigated compounds.

Solvatochromic behavior of the electronic absorption spectra of gallic acid and some of its azo derivatives

The electronic absorption spectra of gallic acid and its azo derivatives have been studied in various solvents of different polarities. Multiple regression techniques were applied to calculate the regression and correlation coefficients based on an equation that relates the wavenumbers of the absorption band maxima (υ(max)(-)) to the solvent parameters; refractive index (n), dielectric constant (D), empirical Kamlet-Taft solvent parameters, π*(dipolarity/polarizability), α (solvent hydrogen-bond donor acidity) and β (solvent hydrogen-bond acceptor basicity). The fitting coefficient obtained from this analysis allows estimating the contribution of each type of interactions relative to total spectral shifts in solution. The dependence of υ(max)(-) on the solvent parameters indicates that the obtained bands are affected by specific and non-specific solute-solvent interactions.

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

The solvatochromic responses of uric acid (Ua), 6-amino-2-thiouracil (ATU) and a series of their complexes dissolved in ten solvents of different polarity have been measured. The solvent-dependent UV/Vis spectroscopic absorption maxima, λ(max), are assigned to the corresponding electronic transitions and analyzed using SPSS program, regression analysis and Kamlet and Taft methods. The observed solvatochromism is discussed using various solute-solvent interaction mechanisms. The electronic absorption spectra of ATU were investigated in aqueous buffer solutions of varying pH and utilized for the determination of dissociation constants. The ranges of pH, where individual ionic species are predominant have been determined.

Reversal in solvatochromism in some novel styrylpyridinium dyes having a hydrophobic cleft

The influence of solvent polarity on the electronic transition of four different N-hexadecyl styrylpyridinium dyes has been investigated in 15 solvents. The E(T)(30) scale has been used to propose a quantitative approach towards the relative stability of the electronic ground and excited state species. The extents of contribution of dipolar aprotic solvents towards the solvation of the excited species have been determined to be 42-48% for some of the dyes. Instead of a steady solvatochromism, all the dyes suffer a reversal in solvatochromism. The transitions of the solvatochromism, referred to as solvatochromic switches, are found to be at E(T)(30) values of approximately 50 for methyl and N,N-dimethylamino substituted dyes while at 37.6 for hydroxyl substituted dye and approximately 45 for 4-(1-methyl-2-phenylethenyl) pyridinium dye. A reversal in the trend of solvent effect in the later dye corresponding to 4-(4-methyl styryl)pyridinium dye has been attributed to an analogy of series and parallel electron flow.

Synthesis, spectral characterisation of 2-(5-methyl-1H-benzimidazol-2-yl)-4-bromo/nitro-phenols and their complexes with zinc(II) ion, and solvent effect on complexation

2-(5-Methyl-1H-benzimidazol-2-yl)-4-bromo/nitro-phenols (HLBr and HLNO2) and their Zn(II) complexes with ZnX2 (X = Cl, I, NO3) were synthesized and characterized by elemental analysis, molar conductivity, IR, 1H and 13C NMR spectra. The OH proton appears near the NH protons in the 1H NMR spectra of the ligands because of the strong intramolecular hydrogen bonding between the OH hydrogen and the C=N nitrogen atoms. The complexation is investigated in ethanol and isopropanol and it is observed that isopropanol is a better solvent than ethanol for the complex forming. HLBr gives harder complexation reaction with Zn(II) according to HLNO2 because of the stronger intramolecular hydrogen bonding in HLBr, and the both ligands react easier with Zn(NO3)2 than ZnCl2 and ZnI2. The Zn(II) complexes of HLBr have 1:1 M:L ratio and ionic character, however, HLNO2 give a non-ionic complex that has 1:2 M:L ratio. In the complexes the phenolic hydrogen is eliminated and a chelate structure is formed.