Potentiometric and spectrophotometric investigation of nickel-monoethanol-amine complexes

Abstract

A detailed study of nickel-monoethanolamine complexes has been made employing potentiometric and spectrophotometric methods. The conditions for the formation of mono as well as polynuclear complexes have been investigated by potentiometric method. Evidence is presented for the formation of the following complexes and their stability constants are determined: NiA 2+, Ni 2 2+, Ni 3 2+, NiA 4 2+, NiA 5 2+, NiA 2 2+, Ni 2A 2 4+ and Ni 3A 3 6+. Combining potentiometric data with the spectrophotometric data, absorption spectra of the pure mononuclear complexes Ni A 2+ to Ni A 4 2+ and Ni A 2+ 6 have been computed. The absorption spectrum of Ni A 2+ 6 has been discussed on the basis of ligand field and molecular orbital theories. The absorption spectra of intermediate complexes have been interpreted on the basis of average ligand field theory. There has been good agreement between the experimental (10,400 cm −1) value of 10 Dq of Ni A 2+ 6 and the calculated value of 10 Dq (11,400 cm −1) on the basis of M.O. theory.