Spectroscopic and Computational Study of the Chemical Reduction of [co(dpgh)2cl(ina)] on the Surface of the Nanocrystalline Titanium Dioxide

The Cobaloxime [Co(dpgH)2Cl(INA)], where dpgH represents diphenylglyoximato and INA stands for isonicotinic acid, was synthesized. The electrochemical behavior was studied using cyclic voltammetry, revealing a cathodic wave at -0.46 V (Co(III)/Co(II)), an anodic wave at +0.20 V (Co(II)/Co(III)), and a reversible curve at -0.83 V vs Ag/AgCl, attributed to the Co(II)/Co(I) transition. The presence of a carboxylic acid group in cobaloxime allows anchoring of the complex to nanocrystalline titanium dioxide thin films. The adsorption equilibrium was investigated using the Langmuir isotherm, yielding a Kad value of 4.7 x 104 M-1. Furthermore, upon addition of NaBH4 to a TiO2 film sensitized with cobaloxime, new bands appeared in the visible spectrum at 450 and 700 nm. The origin of these bands was investigated through theoretical calculations at the DFT/B3LYP/6-311G+(d) level of theory, which can be described as metal-to-ligand charge transfer.