Stability constants for complex formation between cobalt(II), nickel(II), copper(II) and 2,3-diaminopropionic acid, 2,4-diaminobutyric acid, ornithine, lysine, and arginine

Abstract

The formation constants of the complexes formed between H⁺, Co²⁺, Ni²⁺, and Cu²⁺ and DL-2,3-diaminopropionic acid, L-2,4-diaminobutyric acid, L-ornithine, L-lysine, and L-arginine have been measured potentiometrically at 25 °C and I= 0.10 mol dm^–3(K[NO₃]). At intermediate pH values the equilibria have been shown to include a complicated range of protonated complexes with ligands behaving as either bi-or tri-dentate ligands depending on the pH and separation of the nitrogen donor atoms. Probable structures for the various complexes are discussed.