تحضير وتشخيص وتقدير طيفي لأيونات الكوبلت(II) والنيكل(II) والنحاس(II) باستخدام كاشفي شف وآزوشف جديدة

Preparation, Characterization and Spectrophotometric determination of Cobalt(II), Nickel(II) and Copper(II) ions using new Schiff and Azo Schiff reagents

The study included the preparation and Characterization of two azo-azomethine and azomethine reagents for the determination of small quantities of the heavy metal ions cobalt(II), nickel(II) and copper(II) by forming colored complexes with them, The first reagent was prepared by the traditional diazotization method, in two steps. The first step included (Azo preparation) from react (5-aminosalicylic) with nitros acid to form diazonium salt and then diazonium salt reaction with (salicylic aldehyde) to form azo, and the second step(Schiff base preparation) is reaction the product from step one with (Thiosemicarbazide) to give the reagent
5-((3-(2-carbamothioylhydrazineylidene)methyl-4-hydroxyphenyl )diazenyl)-2-hydroxybenzoic acid (CMHPHB)
As for the second reagent, it was prepared in one step via the reflux reaction by react the compound (3-methylthiophene-2-carbaldehyde) with the compound (Thiosemicarbazide) to give the reagent 2-((3-methylthiophen-2-yl)methylene)hydrazine-1-carbothioamide (MTMHC)
Reagents charactrazation using ultraviolet-visible (UV-Vis) and infrared spectra (FT-IR) and nuclear magnetic resonance for proton and carbon (1H-NMR, 13C-NMR), while the complexes were charactrazation using the ultraviolet-visible (UV-Vis) and infrared spectrum (FT-IR), and some physical properties of the complexes were studied, such as solubility, melting point, and electrical conductivity.
Also the optimum conditions for the formation of complexes were determined, such as the effect of the pH, the effect of the concentration of the reagent solution, the effect of the time period for the stability of the complexes formed after 24 hours, which were almost constant, which proves that the prepared complexes are of high constancity and stability, and the effect of temperature, and it was found that they are stable at (10-25)°C. As well as the order of addition, the range of linear concentrations that obey the Beer-Lambert law were determined through calibration curves, They were within the range (0.2946 – 5.893) ppm for the cobalt (II) complex and (0.2934 – 5.869) ppm for the nickel (II) complex and (0.476 – 6.354) ppm for the copper(II) complex of the reagent (CMHPHB), (0.2946 – 5.893) ppm for the cobalt(II) complex, (0.1467-5.869) ppm for the nickel(II) complex, and (0.1588-3.177) ppm for the copper(II) complex of the reagent (MTMHC). Also, the molar absorption coefficient, the sandell’s sensitivity, and the correlation coefficient for the spectrophotometric estimation method were determined.
Also the equivalence of the prepared complexes was studied to finding the ratio of the reagent to the metal ion using the two methods, molar ratios and continuous changes(Job method), The results showed that the ratio was (1:2) (Metal: reagent) for all complexes and for both reagents.
The stability constants for the complexes were also calculated and were found to be highly stable, the stability constants were (1.5678×108 L.mol-1) (4.1850×108 L.mol-1) (4.6314×108 L.mol-1) for the complexes Cobalt(II), Nickel(II) and Copper(II) respectively with reagent (CMHPHB). and (3.8054×108 L.mol-1) (3.4463×108 L.mol-1) (8.2495×108 L.mol-1) for the Cobalt(II), Nickel(II), and Copper(II) complex, respectively with reagent (MTMHC).
The thermodynamic functions (ΔG°, ΔH°, ΔS°) were also calculated for the prepared complexes under study at a range of temperatures (15-65) °C, It was found that the stability constants of the complexes for both reagents decrease with increasing temperatures because they are heat-exothermic reactions, and the formation reactions of all Complexes occur spontaneously, and this is what was observed through the change values of the standard gibbs free energy. The charge of the dissolved complexes was determined using an electrical conductivity device. The result was that all the complexes were uncharged, From all of the above, are propose the octahedral geometric shape of the complexes under study.
The precision, accuracy and sensitivity of the spectrophotometric analytical method used were also determined by using standard solutions of the selected ions with standard solutions of the two reagents at three different concentrations, From these, both the standard deviation and the relative standard deviation, whose limits were no more than (3.000%), and calculate the percentage relative error, whose limits were no exceeds (±5.000), and calculate the recovery ratio, and from this results we conclude that the spectroscopic method used has good accuracy, precision, and sensitivity.
From the above results, we conclude that the spectrophotometric method is fast, economical, environmentally friendly, easy to apply, has good precision, high sensitivity and selectivity.