Azo derivative of 2-thenoyltrifluoroacetone as a reagent for the photometric determination of copper(II)

1-(2-Thenoyl)-4-trifluoro-2-[2-hydroxy-3-sulfo-5-nitrophenylazo]butadione-1,3 (H2L) was synthesized from 2-thenoyltrifluoroacetone. The formation of a copper(II) complex of the synthesized reagent was studied in the presence and absence of 8-hydroxyquinoline (HR). Monoligand [Cu(HL)(2)] and mixed-ligand [Cu(HL)(2)HR] compounds were obtained at pH 4 and 3, respectively. The ratio of components in the monoligand and mixed-ligand compounds were 1 : 2 and 1 : 2 : 1, respectively. Beer's law was obeyed in the ranges of copper concentrations from 0.20 to 2.56 and from 0.25 to 2.56 mug/mL, respectively. The dissociation constants of the reagent were pK(1) = 4.25 +/- 0.01 and pK(2) = 8.20 +/- 0.01. The stability constants of [Cu(HL)(2)] and [Cu(HL)(2)HR] complexes were logK(1) = 4.96 +/- 0.03 and 4.92 +/- 0.01, respectively. A procedure was developed for the photometric determination of copper(II) in rocks.