Heavy metal complexes with 2-hydroxyarylazothiophenes

Spectrophotometric methods have been used to study 2-(3', 4'-dioxiphenyl)-azo-3-cyano-4-methyl-5-ethoxy-carbonylthiophene (I) and its complex compounds with Ge(IV)-, Zr(IV)-, and v(V)-ions. Ionization ionstants (I) in aqueous ethanol solution are determined to be pK=6.29+-0.02; pK2=11.53+-0.02. The maximum of the non-ionized form (I) is observed at 460 nr (E460=2.15x104). In a weakly acidic medium complexes (I) with germanium (IV)-, zirconium (IV)- and vanadium (5)aions are formed. Their molar absorption coefficients are 2.87x104; 250x104; 3.61x104 respectively. The composition of compleXes determined by the Asmus method, equilibrium shift and relative outpUt is M:R=1.1 The equilibrium constants are determined. The Beer law is obserVed in the range of 0.6-4 μg/ml Ge, 0.2-3.6 μg/ml Zr, and 0.2-3.2 μg/ml V