Electrochemical Synthesis of Ni(II) and Al(III) Metalloporphyrins Assisted by Ultrasound

The electrochemical synthesis of Ni(II) and Al(III) metalloporphyrins by the reaction of the radical dianion of the 5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin (TPPOH) with Ni(II) and Al(III) ions is reported. The electrosynthesis conditions were stablished by cyclic voltammetry of TPPOH. The electrosynthesis process was carried out in an undivided cell at the potential corresponding to the formation of the porphyrin dianion radical. A sacrificial anode of Ni or Al was used to electrogenerate the ions. The experiments were carried out in aprotic and protic solvents to evaluate the effect of the solvent. The effect of the application of 20 kHz ultrasound on the electrochemical process was also evaluated. The electrosynthesis products were characterized by spectroscopy and electrochemical techniques. The results indicate the formation of metalloporphyrins in the different solvents in silent conditions and with ultrasound. The application of 20 kHz ultrasound and protic solvents enhance the reaction yields without affecting the electrochemical reaction mechanism.