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A 2:2:2 Complex of Vanadium(V) with 4-(2-Thiazolylazo)orcinol and 2,3,5-Triphenyl-2H-Tetrazolium Chloride

Kiril Blazhev Gavazov, Vassil Borisov Delchev, Kremena Tomova Mileva, Teodora Stefcheva Stefanova, Galya Kostadinova Toncheva


The complex formation in the vanadium(V) / 4-(2-thiazolylazo)orcinol (TAO) / 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) liquid-liquid extraction-chromogenic system was studied. The chloroform-extracted complex has a composition of 2:2:2 under the optimum conditions (pH 4.8–5.2, extraction time 3 min, concentration of TAO 3.4´10–4 mol dm–3, and concentration of TTC 9.4´10–4 mol dm–3) and could be regarded as a dimer (D) of two 1:1:1 species (S) presented by the formula (TT+)[VO2(TAO)]. The constant of extraction was calculated by two methods and some analytical characteristics were determined. The wavelength of maximum absorption (lmax), molar absorptivity (el) and fraction extracted (E) were found to be l = 545 nm, e545 = 1.97´104 dm3 mol–1 cm–1, and E = 97.9 %. The ground-state equilibrium geometries of the complexes S and D were optimized by quantum chemical Hartree-Fock calculations using 3-21G* basis functions. The bonding and interaction energies were calculated as well.


liquid-liquid extraction; spectrophotometry; tetrazolium salt; 5-methyl-4-(2-thiazolylazo)resorcinol; 2:2:2 complex; HF calculations

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