Effective Complexation of Tris-Ligand with CoCl₂·6H₂O in an Aqueous Solution: Suppressing Electrochemical Formation of CoO_<i>x</i>

In this report, we have demonstrated an effective complexation of <b>TrisH</b>_<b>3</b> (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)] (<b>CoT</b>), in the resultant solution at a pH value of 8.6. We could characterize the <b>CoT</b> 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 <b>TrisH</b>_<b>3</b> and CoCl₂·6H₂O. Interestingly, this complex (<b>CoT</b>) in its solution state inhibits the formation of CoO_<i>x</i> during electrochemical studies, whereas the aqueous solution of CoCl₂·6H₂O <i>per se</i> generates CoO_<i>x</i> <i>in situ</i>. The relevant electrochemical and spectroscopic studies, including controlled experiments, have been performed in this work.