PtIV-oxaloyldihydrazone complexes: synthesis, characterization, optical properties and corrosion inhibition on carbon-steel in hydrochloric acid solution

Platinium(IV) hydrazone complexes derived from oxaloyldihydrazide and selected aldehydes, namely salicyaldehyde (L 1 ), 2-hydroxynaphthaldehyde (L 2 ), o-hydroxyacetophenone (L 3 ) and o-methoxybenzaldehyde (L 4 ) have been synthesized and characterized. The mode of bonding as well as the structure of the isolated compounds have been ascertained on the basis of emental analyses and spectral (UV-Vis., IR, mass, 1 H NMR) measurements. The synthesized dihydrazones coordinate to the metal center either dibasic or tetrabasic hexadentate ligands forming binuclear complexes in all cases. The metal center in all investigated complexes has octahedral stereochemistry. Ligands L 1 and L 3 bind with Pt(IV) ion in diketo forms while L 2 and L 4 employed their dienol skeletons. Optical transmission spectra were recorded in the range 190–2100 nm and some optical parameters such as indirect optical band gap and refractive index have been determined. The inhibitive and adsorptive properties of all ligands for the corrosion of carbon-steel in 1 M HCl solutions were investigated using weight loss technique. The results pointed out that the ligands have reasonable inhibitions towards the corrosion of carbon-steel. The adsorption of the inhibitors on metal surface was found to be spontaneous and consistent with the mechanism of physical adsorption. The adsorption data fitted well to Freundlich, Langmuir and Frumkin adsorption isotherms.