title: Spectroscopic and Kinetic Characterization of Peroxidase-Like π-Cation Radical Pinch-Porphyrin-Iron(III) Reaction Intermediate Models of Peroxidase Enzymes.
abstract: The spectroscopic and kinetic characterization of two intermediates from the H₂O₂ oxidation of three dimethyl ester [(proto), (meso), (deuteroporphyrinato) (picdien)]Fe(III) complexes ([FePPPic], [FeMPPic] and [FeDPPic], respectively) pinch-porphyrin peroxidase enzyme models, with s = 5/2 and 3/2 Fe(III) quantum mixed spin (qms) ground states is described herein. The kinetic study by UV/Vis at λmax = 465 nm showed two different types of kinetics during the oxidation process in the guaiacol test for peroxidases (1-3 + guaiacol + H₂O₂ → oxidation guaiacol products). The first intermediate was observed during the first 24 s of the reaction. When the reaction conditions were changed to higher concentration of pinch-porphyrins and hydrogen peroxide only one type of kinetics was observed. Next, the reaction was performed only between pinch-porphyrins-Fe(III) and H₂O₂, resulting in only two types of kinetics that were developed during the first 0-4 s. After this time a self-oxidation process was observed. Our hypotheses state that the formation of the π-cation radicals, reaction intermediates of the pinch-porphyrin-Fe(III) family with the ligand picdien [N,N'-bis-pyridin-2-ylmethyl-propane-1,3-diamine], occurred with unique kinetics that are different from the overall process and was involved in the oxidation pathway. UV-Vis, ¹H-NMR and ESR spectra confirmed the formation of such intermediates. The results in this paper highlight the link between different spectroscopic techniques that positively depict the kinetic traits of artificial compounds with enzyme-like activity.
authors.affiliation: Centro de Qu&#237;mica Instituto de Ciencias, Benem&#233;rita Universidad Aut&#243;noma de Puebla. Edificio 103H, Ciudad Universitaria, Col. Jardines de San Manuel, Puebla, Pue. 72570, Mexico. samuel.hernandezan@correo.buap.mx.
authors.forename: Samuel
authors.initials: S
authors.lastname: Hernández Anzaldo
authors.affiliation: Centro de Qu&#237;mica Instituto de Ciencias, Benem&#233;rita Universidad Aut&#243;noma de Puebla. Edificio 103H, Ciudad Universitaria, Col. Jardines de San Manuel, Puebla, Pue. 72570, Mexico. uri_creek@hotmail.com.
authors.forename: Uriel
authors.initials: U
authors.lastname: Arroyo Abad
authors.affiliation: Centro de Qu&#237;mica Instituto de Ciencias, Benem&#233;rita Universidad Aut&#243;noma de Puebla. Edificio 103H, Ciudad Universitaria, Col. Jardines de San Manuel, Puebla, Pue. 72570, Mexico. armando_leon2@yahoo.es.
authors.forename: Armando
authors.initials: A
authors.lastname: León García
authors.affiliation: Instituto Polit&#233;cnico Nacional, ESFM, Ave. Instituto Polit&#233;cnico Nacional S/N, Edif. 9 U.P. Zacatenco, Col. San Pedro Zacatenco, M&#233;xico City 07738, Mexico. danielesfm@yahoo.com.mx.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ramírez Rosales
authors.affiliation: Instituto Polit&#233;cnico Nacional, ESFM, Ave. Instituto Polit&#233;cnico Nacional S/N, Edif. 9 U.P. Zacatenco, Col. San Pedro Zacatenco, M&#233;xico City 07738, Mexico. davozam@yahoo.com.
authors.forename: Rafael
authors.initials: R
authors.lastname: Zamorano Ulloa
authors.affiliation: Centro de Qu&#237;mica Instituto de Ciencias, Benem&#233;rita Universidad Aut&#243;noma de Puebla. Edificio 103H, Ciudad Universitaria, Col. Jardines de San Manuel, Puebla, Pue. 72570, Mexico. yasmi.reyes@correo.buap.mx.
authors.forename: Yasmi
authors.initials: Y
authors.lastname: Reyes Ortega
mesh_terms: D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000737:chemistry* / Q000378:metabolism*; D011166:Porphyrins / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D011166:Porphyrins; C028565:porphyrin pi cation radical; D006861:Hydrogen Peroxide; D007501:Iron; D009195:Peroxidase
keywords: peroxidases models; pinch-porphyrins; spectroscopic studies; π-cation radical