Complexation and redox processes during the course of AuCl4−–bilirubin interaction in aqueous–basic and methanolic media

The AuCl4−–bilirubin (BR) interaction, both in aqueous–basic and methanolic media was studied using u.v.–vis., e.p.r. and 197Au mossbauer spectroscopy. It was established that, during the course of the reaction, multistep redox and complexation processes occur. BR is oxidized according the reaction scheme: Bilirubin (BR) → Biliverin (BVD) → Purpurine (PRN) accompanied with AuIII reduction to Au0 and complexation, resulting in spontaneous formation of an Au3PRN precipitate. By means of quantitative u.v.–vis. spectroscopic studies some of the rates and stability constants wee determined. The most probable reaction scheme is proposed.