Solvatochromism and halochromism of some furo/pyrazole cyanine dyes

In this study, the electronic absorption spectra of some furo[2,3-b]pyrazole cyanine dyes was recorded and investigated in a number of 6 (six) pure solvents having different polarities [water (78.54), D.M.F (36.70), ethanol (24.3), chloroform (4.806), CC14 (2.238) and dioxane (2.209)], mixed solvents [DMF- H2O] and/or in a series of 8 (eight) aqueous universal buffer solutions having varied pH values [1.65, 2.32, 4.62, 5.85, 6.41, 7.82, 9.61 and 11.63 units] to evaluate their solvatochromic and/or halochromic properties, respectively. The study covers different types of cyanine dyes, it includes monomethine cyanine dyes (simple cyanine dyes), dimethine cyanine dyes and tetramethine cyanine dyes.

Novel carbocyanine and bis-carbocyanine dyes: synthesis, visible spectra studies, solvatochromism and halochromism

Novel carbocyanine dyes (trimethine cyanine dyes) and bis-carbocyanine dyes (bis-trimethine cyanine dyes) derived from the nucleus of benzo[2,3-b; 2',3'-b'] bis-furo[2,3-d]imidazoline-3,5,8,10-tetra one were synthesized. The electronic visible adsorption spectra of all the synthesized cyanine dyes were investigated in 95% ethanol solution. Solvatochromism and/or halochromism for some selected dyes were examined in pure solvents having different polarities (water, dimethylformamide, ethanol, chloroform, carbontetrachloride and dioxane) and/or in aqueous universal buffer solutions owing varied pH values (1.45, 2.03, 3.72, 5.09, 7.57, 8.91, 10.20 and 12.04 units), respectively. Structural confirmations were determined by elemental analysis, visible, mass, IR and 1H NMR spectral data.

Characterization of Palladium Chelates and Their Interactions with Z-N'-(Benzo(d)Thiazol-2-yl)-N,N-Dimethylformimidamide using the Spectrophotometric and Computational Methods

A rapid, selective and sensitive method for the quantification of Pd (II) using spectrophotometric technique associated with Z-N'-(benzo(d) thiazol-2-yl)-N,N-dimethylformimidamide BTDF as new chelating agent is described. Yellow colored complex of Pd (II) with BTDF is formed in Britton-Robinson universal buffer of pH 9 and extracted with chloroform. The formed complex clearly illustrate an absorption at ∼384 nm and follw Beer’s law in the range of concentration between 0.5–18.0 µg ml−1 of Pd (II) with absorbance of 3.62 × 104 L mol-1 cm-1 and limit of detection(LOD) of Pd (II) 0.07 µg ml−1. The effects of different experimental parameters have been established by study the optimum conditions for the extraction and quantification of palladium ion. Density functional theory (DFT) havealso been employed to computethe influence of the cation on theoretical parameters of Pd2+ complexes. The effect of donating centers was investigated theoretically which prove that Pd2+ favor coordinated with two molecules of Z-N'-(benzo(d)thiazol-2-yl)-N,N-dimethylformimidamide through two nitrogen atoms.The performance of the examined method was estimated to detect the impact of current method over the presented methods in the literature without interference effect of cations and anions. The examined method has successfully demonstrated the quantification of Pd(II) in natural and spiked water samples.

Electrocatalytic reduction of dioxygen by Mn(iii) meso-tetra(N-methylpyridinium-4-yl)porphyrin in universal buffer

The electrochemical characterization of manganese(iii) meso-tetra(N-methylpyridinium-4-yl)porphyrin pentachloride via cyclic voltammetry (CV) and UV-vis spectroelectrochemistry (UV-vis SEC) was performed to examine O2 reduction in aqueous conditions.

Assessment and kinetics of soil phosphatase in Brazilian Savanna systems

The activity and kinetics of soil phosphatases are important indicators to evaluate soil quality in specific sites such as the Cerrado (Brazilian Savanna). This study aimed to determine the activity and kinetic parameters of soil phosphatase in Cerrado systems. Soil phosphatase activity was assessed in samples of native Cerrado (NC), no-tillage (NT), conventional tillage (CT) and pasture with Brachiaria brizantha (PBb) and evaluated with acetate buffer (AB), tris-HCl buffer (TB), modified universal buffer (MUB) and low MUB. The Michaelis-Menten equation and Eadie-Hofstee model were applied to obtain the kinetic parameters of soil phosphatase using different concentrations of p-nitrophenol phosphate (p-NPP). MUB showed the lowest soil phosphatase activity in all soils whereas AB in NC and NT presented the highest. Low MUB decreased interferences in the assessment of soil phosphatase activity when compared to MUB, suggesting that organic acids interfere on the soil phosphatase activity. In NC and NT, soil phosphatase activity performed with TB was similar to AB and low MUB. Km values from the Michaels-Menten equation were higher in NC than in NT, which indicate a lower affinity of phosphatase activity for the substrate in NC. Vmax values were also higher in NC than in NT. The Eadie-Hofstee model suggests that NC had more phosphatase isoforms than NT. The study showed that buffer type is of fundamental importance when assessing soil phosphatase activity in Cerrado soils.

VOLTAMMETRIC DETERMINATION OF ACETOPHOS IN WATER SAMPLES AT CNTPE

In this paper, a sensitive differential pulse voltammetric method to determine the residues of acetophos in water samples at CNTPE were reported. The significance of CNTPE is to result in low detection limits, high sensitivities, reduction of over-potentials, high mechanical strength and high conductivity and resistance to surface fouling. The universal buffer with pH range 2.0–6.0 is used as supporting electrolyte. Cyclic voltammetry employed to evaluate electrode mechanism and number of electrons involved in reduction process were found out by using Millicoulometry and the product collected by applying Controlled potential electrolysis. Experimental conditions such as accumulation potential, accumulation time and scan rate were optimized. Calculations were made by standard addition method.