Study of the CuII Affiinity by Three Chelating Agents of Biological Interest: TPEN, TRIEN and Et2DTC

Copper is an important micronutrient, and it is present in some protein structures, as well as participate in several important biological processes. Due to its importance, some ligands are used and studied like carriers of copper in the biological systems. This work has investigated the affinity of Cu-II by three ligands of biological interest: N,N,N,N'-tetrakis (2-pyridilmethyl) ethylenediamine (TPEN), triethylenetetramine (TRIEN), and diethyldithiocarbamate (Et2DTC), used for this purpose. The studies were performed by evaluating the Cu-II d-d band when complexed with these three ligands. The Cu-II d-d band in aqueous solution appears around 800 nm; when in the presence of TRIEN, this band displaces to 576 nm. TRIEN ligand is substituted by TPEN ligand (d-d band at 689 nm), and finally, in the presence of the Et2DTC ligand, the d-d band displaces to 665 nm. Theoretical calculations were used to obtain the binding energy and the values obtained were -481.85 kcal mol(-1) for the Cu-II-TPEN, -417.80 kcal mol(-1) for Cu-II-TRIEN and -726.72 kcal mol(-1) for Cu-II-Et2DTC. Electrochemical studies showed an oxidation peak at 0.008 V to Cu-II-TRIEN complex, -0.135 V to Cu-II-TPEN and 0.150 V to Cu-II-Et2DTC. These results showed that Cu-II has a higher affinity by the Et2DTC ligand compared to the other ligands studied.