Participation of nanocrystalline TiO$_{2}$ surface in the electron transfer between semiconductor solid and adsorbed cobalt(III)-Rpy complex

Cis-[Co$^{\mathrm{III}}$(tn)$_{2}$(Rpy)Br]Br$_{2}$, (R = 4-CN, H, 4-Bz, 4-Me, 4-Et, and 4-MeNH), in aqueous 2-propanol exhibit varying adsorption characteristics and led to surface compound formation. UV ($\lambda$ = 254) excitation of the nano-TiO$_{2}$//cobalt(III)-(Rpy) surface compound resulted in interfacial electron transfer (IFET) reaction. The IFET has been found to be dependent upon the coordination environment of the complex, more precisely due to the Rpy ligand. In addition, the proposed mechanism of the IFET reaction includes the formation of a Co$^{\mathrm{II}}$ ion implanted in nanocrystalline TiO$_2$. This photoreduction was found to be solvent controlled. The photoefficiency of the Co$^{\mathrm{II}}_{aq}$ formation was spectrally analyzed simultaneously as Co$^{\mathrm{II}}$:TiO$_{2}$ was isolated from the photolyte solution. The isolated solid was subjected to FTIR, DRS, PXRD, and SEM-EDX instrumental analysis. It is concluded that the removal of metal ion in the form of a complex is coordination structure dependent, hence, seems more specific in removal efficiency and in doping the anatase lattice.