COMPLEXATION OF 6,7-DIHYDROXY-4-CARBOXYL- 2-PHENYLBENZOPYRYLIUM SALTS WITH MO (VI) AND W (VI) IN AQUEOUS SOLUTIONS AND ORGANIZED MEDIA
DOI:
https://doi.org/10.32782/naturaljournal.13.2025.21Keywords:
Molybdenum (VI), Tungsten (VI), spectrophotometry, complexation, 6,7-dihydroxy-4-carboxyl- 2-phenylbenzopyrylium salts, surfactantsAbstract
This work is devoted to the study of the features of complexation of Molybdenum (VI) and Tungsten (VI) with some salts (bromide, perchlorate chloride) of 6,7-dihydroxy-4-carboxyl-2-phenylbenzopyrylium (R) in aqueous solutions and organized media based on cationic surfactants. Spectrophotometric methods for complexation studies in solutions were used. It was established that in binary systems one complex with a stoichiometry of M (VI) : R 1 : 2 is formed at pH 2,5 and 3,0, respectively, for Molybdenum (VI) and Tungsten (VI). The molar absorptivity values for Molybdenum (VI) and Tungsten (VI) complexes with R are 3,0 ⸱ 104 and 3,1 ⸱ 104, respectively. It has been established that when cationic surfactants, namely cetylpyridinium chloride and cetyltrimethylammonium bromide, are introduced into the systems, the formation of ternary complexes with a stoichiometry of 1 : 2 : 2 is observed. It was found that the color develops instantly, and the absorbance of the resulting solutions is unchanged for 2 hours.It is noted that the nature of the anion, which is part of the reagent R, does not significantly change the analytical properties of the proposed analytical forms. The introduction of cationic surfactants results in a shift of the optimal pH for complex formation toward more acidic values. It has been shown that the introduction of cationic surfactants shifts the optimal pH value of complexation to a more acidic region and leads to bathochromic shifts of the absorption bands of the interaction products by 30–40 nm and an increase in the values of the molar absorptivity to 6,4 ⸱ 104 and 7,9 ⸱ 104 (for W (VI): 6,7 ⸱ 104 and 8,1 ⸱ 104) for cetylpyridinium chloride and cetyltrimethylammonium bromide, respectively. The identified analytical forms may serve as a foundation for the creation of novel combined spectroscopic techniques for the determination of trace levels of Molybdenum (VI) and Tungsten (VI).
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