Abstract
Two new vanadium (V) complexes involving 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR) and tetrazolium cation were studied. The following commercially available tetrazolium salts were used as the cation source: tetrazolium red (2,3,5-triphenyltetrazol-2-ium;chloride, TTC) and neotetrazolium chloride (2-[4-[4-(3,5-diphenyltetrazol-2-ium-2-yl)phenyl]phenyl]-3,5-diphenyltetrazol-2-ium;dichloride, NTC). The cations (abbreviated as TT(+) and NTC(+)) impart high hydrophobicity to the ternary complexes, allowing vanadium to be easily extracted and preconcentrated in one step. The complexes have different stoichiometry. The V(V)-HTAR-TTC complex dimerizes in the organic phase (chloroform) and can be represented by the formula [(TT(+))[VO(2)(HTAR)]](2). The other complex is monomeric (NTC(+))[VO(2)(HTAR)]. The cation has a +1 charge because one of the two chloride ions remains undissociated: NTC(+) = (NT(2+)Cl(-))(+). The ground-state equilibrium geometries of the constituent cations and final complexes were optimized at the B3LYP and HF levels of theory. The dimer [(TT(+))[VO(2)(HTAR)]](2) is more suitable for practical applications due to its better extraction characteristics and wider pH interval of formation and extraction. It was used for cheap and reliable extraction-spectrophotometric determination of V(V) traces in real samples. The absorption maximum, molar absorptivity coefficient, limit of detection, and linear working range were 549 nm, 5.2 × 10(4) L mol(-1) cm(-1), 4.6 ng mL(-1), and 0.015-2.0 μg mL(-1), respectively.