Redox potential determines the mechanism of azanone donor reactions with Mn and Fe Porphyrins: defining the best HNO traps

LUCÍA ÁLVAREZ; SEBASTIAN SUAREZ; DAMIAN BIKIEL; INES BATINI HABERLE; JULIO S REBOUCAS; MARCELO A. MARTÍ ; FABIO DOCTOROVICH

INORGANIC CHEMISTRY

AMER CHEMICAL SOC

Lugar: Washington; Año: 2014

0020-1669

Azanone (1HNO, nitroxyl), is a highly reactive molecule, with interesting chemical and biological properties. Like nitric oxide (NO), its main biologically related targets are oxygen, thiols and metalloproteins, particularly heme proteins. As HNO dimerizes with a close to diffusion-controlled rate constant, reactive studies are performed using donors, which are compounds that spontaneously release HNO in solution. In the present work, we have studied the reaction mechanism and kinetics of the most widely used azanone donors Angeli´s Salt and toluene sulfohydroxamic acid (TSHA) with eight different Mn porphyrins as trapping agents. These porphyrins differ systematically in their total peripheral charge (positively, negatively charged, and neutral) and in their MnIII/MnII reduction potential, showing for each case positive (oxidizing) and negative (reducing) values. Our results show that it is not the previously suspected peripheral charge, but the redox potential what determines the azanone donor reaction mechanism. While oxidizing porphyrins catalyze the decomposition of the donor, reducing porphyrins react with free HNO. Our results also shed light into the donor decomposition mechanism using ab-initio methods, and provide a thorough analysis of which MnP are the best candidates for azanone trapping and quantification experiments