Effective Complexation of Tris-Ligand with CoCl2·6H2O in an Aqueous Solution: Suppressing Electrochemical Formation of CoOx

In this report, we have demonstrated an effective complexation of TrisH₃ (tris(hydroxymethyl)aminomethane) ligand with Co(II) when it is added to a sodium acetate containing aqueous solution of CoCl₂·6H₂O, leading to the formation of a Co(II)-coordination complex, [Co^II(TrisH₂)(TrisH₃)(CH₃COO) (H₂O)] (CoT), in the resultant solution at a pH value of 8.6. We could characterize the CoT complex in its solution state by diverse spectral analyses followed by its validation using computational (density functional theory (DFT)) studies. The Job plot from UV–visible data indicates a 2:1 Tris/Co coordination complex in the aqueous solution of TrisH₃ and CoCl₂·6H₂O. Interestingly, this complex (CoT) in its solution state inhibits the formation of CoO_x during electrochemical studies, whereas the aqueous solution of CoCl₂·6H₂O per se generates CoO_x in situ. The relevant electrochemical and spectroscopic studies, including controlled experiments, have been performed in this work.