Application of metal complexes as biomimetic catalysts on glycerol oxidation

ADRIÁN PARODI; CAROLINA MERLO; AGOSTINA CÓRDOBA; CLAUDIA PALOPOLI; JOAQUÍN FERREYRA; SANDRA SIGNORELLA; MARÍA LUJÁN FERREIRA; IVANA MAGARIO

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2018

1381-1169

Two biomimetic complexes were evaluated as catalyst in the H2O2 mediated oxidation of glycerol, namely a peroxidase mimetic Fe(III) protoporphyrin complex (hematin) and the superoxide-dismutase mimetic complex of Mn(III) with 1,3-bis(5sulphonatesalycilidenamino)propane (MnL-). Catalysis was targeted to glyceraldehyde since antimicrobial power was proved for it. Glycerladehyde evolved at a higher rate than the uncatalyzed reaction only with hematin acid treated solutions and kinetics were typical of a radical mechanism. Nonetheless, glycerol conversions were low. H2O2 bleached hematin and the immobilization on a porous matrix could not prevent this. Meanwhile, the catalatic activity of hematin was high but its peroxidatic activity was inhibited at pH > 8. Thus, the coordination of hematin compound I to H2O2 over glycerol may be the preferred route with the accumulation of peroxy radicals, able to degrade the porphirinic ring -with probable iron releasing-; but also contributing to glycerol oxidation. On the other hand, a prompt decay with time of the catalatic and peroxidatic activity of MnL- was observed, which was improved by the addition of DMSO, DMF or acetone to the basic buffer system. Finally, EPR spectroscopy of MnL- supported the hypothesis of the formation of inactive bis-oxo-bridged Mn(IV)Mn(IV) dimer upon addition of H2O2.