Environment

[PY1-10] Redox properties of metal complexes with catechol and its derivatives

○Xinlong - Li¹, Kosuke Naruwa¹, Carlito Baltazar Tabelin¹, Mayumi Ito¹, Naoki Hiroyoshi¹ (1. Hokkaido University)

Keywords:CME, Redox properties, Organic chemistry, Electronic theory

Carrier Microencapsulation (CME) has been proposed as a method to suppress pyrite oxidation. In CME, metal catechol complexes are adsorbed and oxidatively decomposed to form oxy-hydroxy metal coating on pyrite surface, acting as protective barrier against oxidation of the mineral. In this study, using Fe³⁺ and Ti⁴⁺ as metal ions, the effects of additional functional group in ligand (catechol derivatives) on the oxidative decomposition of the complexes were investigated by cyclic voltammetry.

In comparison with catechol complex, complexes with catechol derivatives having H₃C-, H₅C₂- and HO- as a functional group were oxidized at lower potentials, while the complexes with catechol derivatives having HOOC- and O₂N- were oxidized at higher potentials. This indicates that the electron-donating groups (H₃C-, H₅C₂- and HO-) could accelerate oxidative decomposition of complexes and electron-withdrawing group (HOOC- and O₂N-) suppresses the decomposition. The tris-catecholate complex with Ti⁴⁺ was oxidized at higher potentials than that of Fe³⁺-catechol complex, implying that central atoms (metal ions) also effect on the oxidative decomposition of the complexes.