title: A glance at the reactivity of osma(II)cycles [Os(C-N)x(bpy)3-x](m+) (x=0-3) Covering a 1.8 V potential range toward peroxidase through Monte Carlo Simulations ((-)C-N=o-2-phenylpyridinato, bpy=2,2'-bipyridine).
abstract: Three cyclometalated and one coordination compounds [Os(C-N)x(bpy)3-x](m) (x/m=0/2+ (4); 1/1+ (3); 2/1+ (2); 3/0 (1); (-)C-N=2-phenylpyridinato, bpy=2,2'-bipyridine) with drastically different reduction potentials have been used for analyzing the second-order rate constants for one-electron, metal-based osmium(II) to osmium(III) oxidation of the complexes by compound I (k2) and compound II (k3) of horseradish peroxidase. Previously unknown k2 and k3 have been determined by digital simulation of cyclic voltammograms measured in phosphate buffer of pH7.6 and 21 ± 1°C. Osmium(II) species derived from osmium(III) complexes 1 and 2 were generated electrochemically in situ. Under the conditions used the reduction potentials for the Os(III/II) feature equal -0.90, -0.095, 0.23 and 0.85V versus NHE (normal hydrogen electrode) for 1-4, respectively. The rate constants k2 equal ~5 × 10(7), 6 × 10(8), 2 × 10(6) and 1 × 10(5)M(-1)s(-1) and the rate constants k3 equal ~9 × 10(6), 4× 10(7), 1 ×10(6) and 1 × 10(5)M(-1)s(-1) for complexes 1-4, respectively. Both rate constants k2 and k3 first increase with increasing the reaction driving force on going from 4 to 2 but then both decrease on going to complex 1 though the reaction driving force is the highest in this case. The system described has been explored theoretically using docking Monte Carlo simulations.
authors: Instituto de Química, UNAM, Circuito Exterior s/n, Ciudad Universitaria, México D.F. 04510, Mexico.
authors: Ricardo
authors: R
authors: Cerón-Camacho
authors: Instituto de Química, UNAM, Circuito Exterior s/n, Ciudad Universitaria, México D.F. 04510, Mexico. Electronic address: ronan@unam.mx.
authors: Ronan
authors: R
authors: Le Lagadec
authors: Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA.
authors: Igor V
authors: IV
authors: Kurnikov
authors: Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA. Electronic address: ryabov@andrew.cmu.edu.
authors: Alexander D
authors: AD
authors: Ryabov
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D055664:Electrochemical Techniques; D004579:Electron Transport; D004583:Electrons; D006735:Horseradish Peroxidase / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D009010:Monte Carlo Method; D009992:Osmium / Q000737:chemistry*; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D010940:Plant Proteins; D009992:Osmium; D015082:2,2'-Dipyridyl; D006735:Horseradish Peroxidase
keywords: Cyclometalation; Electron transfer; Monte Carlo simulations; Osmium; Peroxidase