Spectrophotometric and potentiometric investigations of copper (II)-ethanolamine complexes

Summary

Spectrophotometric and potentiometric investigations have been carried out on copper-monoethanolamine complexes. Job plots at 920, 760 and 620 mµ have indicated the formation of CuA⁺⁺, CuA_2/++ and CuA₃ ⁺⁺. The$\bar n - pA$ curves have been obtained by a slight modification of the method of corresponding solutions and by pH measurements. The$\bar n$ vs. pA curves obtained at different metal concentrations coincide indicating the formation of mononuclear complexes. Experiments conducted with 0·1. 0·2, 0·5 and 1·0 M monoethanolammonium ion indicate the formation of mononuclear hydroxy complexes above pH 6. The nature of E _m vs pA curves is closely analogous to that of$\bar n$ vs. pA curves. Absorption spectra taken at pH 9·8 with different amounts of monoethanolamine has given evidence for the formation of (CuA₃OH·A)⁺.$\bar n - pA$ curves have been analyzed and the values ofβ _{1, 1},β _{1, 2} andβ _{1, 3} have been obtained. Curves showing the distribution of complexes and the absorption curves of the individual complexes (CuA⁺⁺, CuA_2/++, and CuA_3/++) have been calculated.