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Title: Differences of pH-Dependent Mechanisms on Generation of Hydride Donors using Ru(II) Complexes Containing Geometric Isomers of NAD+ Model Ligands: NMR and Radiolysis Studies in Aqueous Solution

Abstract

The pH-dependent mechanism of the reduction of the nicotinamide adenine dinucleotide (NADH) model complex [Ru(bpy)(2)(5)](2+) (5 = 3-(pyrid-2{prime}-yl)-4-azaacridine) was compared to the mechanism of the previously studied geometric isomer [Ru(bpy)(2)(pbn)](2+) (pbn = 2-(pyrid-2{prime}-yl)-1-azaacridine, previously referred to as 2-(pyrid-2{prime}-yl)-benzo[b]-1,5-naphthyridine) in aqueous media. The exposure of [Ru(bpy)(2)(5)](2+) to CO(2)(*-) leads to the formation of the one-electron reduced species (k = 4.4 x 10(9) M(-1) s(-1)). At pH < 11.2, the one-electron reduced species can be protonated, k = 2.6 x 10(4) s(-1) in D(2)O. Formation of a C-C bonded dimer is observed across the pH range of 5-13 (k = 4.5 x 10(8) M(-1) s(-1)). At pH < 11, two protonated radical species react to form a stable C-C bonded dimer. At pH > 11, dimerization of two one-electron reduced species is followed by disproportionation to one equivalent starting complex [Ru(bpy)(2)(5)](2+) and one equivalent [Ru(bpy)(2)(5HH)](2+). The structural difference between [Ru(bpy)(2)(pbn)](2+) and [Ru(bpy)(2)(5)](2+) dictates the mechanism and product formation in aqueous medium. The exchange of the nitrogen and carbon atoms on the azaacridine ligands alters the accessibility of the dimerization reactive site, thereby changing the mechanism and the product formation for the reduction of the [Ru(bpy)(2)(5)](2+) compound.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) Laser Electron Accelerator Facility (Leaf)
Sponsoring Org.:
DOE - Office Of Science
OSTI Identifier:
990714
Report Number(s):
BNL-93759-2010-JA
Journal ID: ISSN 0020-1669; INOCAJ; R&D Project: CO-026; TRN: US201020%%570
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 49; Journal Issue: 17; Journal ID: ISSN 0020-1669
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AQUEOUS SOLUTIONS; ATOMS; CARBON; DIMERIZATION; DIMERS; HYDRIDES; ISOMERS; NAD; NITROGEN; OXIDATION; RADICALS; RADIOLYSIS; REDUCTION; hydrides; laser electron accelerator facility

Citation Formats

Fujita, E, Cohen, B W, Polyansky, D E, Zong, R, Zhou, H, Ouk, T, Cabelli, D, and Thummel, R P. Differences of pH-Dependent Mechanisms on Generation of Hydride Donors using Ru(II) Complexes Containing Geometric Isomers of NAD+ Model Ligands: NMR and Radiolysis Studies in Aqueous Solution. United States: N. p., 2010. Web.
Fujita, E, Cohen, B W, Polyansky, D E, Zong, R, Zhou, H, Ouk, T, Cabelli, D, & Thummel, R P. Differences of pH-Dependent Mechanisms on Generation of Hydride Donors using Ru(II) Complexes Containing Geometric Isomers of NAD+ Model Ligands: NMR and Radiolysis Studies in Aqueous Solution. United States.
Fujita, E, Cohen, B W, Polyansky, D E, Zong, R, Zhou, H, Ouk, T, Cabelli, D, and Thummel, R P. Mon . "Differences of pH-Dependent Mechanisms on Generation of Hydride Donors using Ru(II) Complexes Containing Geometric Isomers of NAD+ Model Ligands: NMR and Radiolysis Studies in Aqueous Solution". United States.
@article{osti_990714,
title = {Differences of pH-Dependent Mechanisms on Generation of Hydride Donors using Ru(II) Complexes Containing Geometric Isomers of NAD+ Model Ligands: NMR and Radiolysis Studies in Aqueous Solution},
author = {Fujita, E and Cohen, B W and Polyansky, D E and Zong, R and Zhou, H and Ouk, T and Cabelli, D and Thummel, R P},
abstractNote = {The pH-dependent mechanism of the reduction of the nicotinamide adenine dinucleotide (NADH) model complex [Ru(bpy)(2)(5)](2+) (5 = 3-(pyrid-2{prime}-yl)-4-azaacridine) was compared to the mechanism of the previously studied geometric isomer [Ru(bpy)(2)(pbn)](2+) (pbn = 2-(pyrid-2{prime}-yl)-1-azaacridine, previously referred to as 2-(pyrid-2{prime}-yl)-benzo[b]-1,5-naphthyridine) in aqueous media. The exposure of [Ru(bpy)(2)(5)](2+) to CO(2)(*-) leads to the formation of the one-electron reduced species (k = 4.4 x 10(9) M(-1) s(-1)). At pH < 11.2, the one-electron reduced species can be protonated, k = 2.6 x 10(4) s(-1) in D(2)O. Formation of a C-C bonded dimer is observed across the pH range of 5-13 (k = 4.5 x 10(8) M(-1) s(-1)). At pH < 11, two protonated radical species react to form a stable C-C bonded dimer. At pH > 11, dimerization of two one-electron reduced species is followed by disproportionation to one equivalent starting complex [Ru(bpy)(2)(5)](2+) and one equivalent [Ru(bpy)(2)(5HH)](2+). The structural difference between [Ru(bpy)(2)(pbn)](2+) and [Ru(bpy)(2)(5)](2+) dictates the mechanism and product formation in aqueous medium. The exchange of the nitrogen and carbon atoms on the azaacridine ligands alters the accessibility of the dimerization reactive site, thereby changing the mechanism and the product formation for the reduction of the [Ru(bpy)(2)(5)](2+) compound.},
doi = {},
url = {https://www.osti.gov/biblio/990714}, journal = {Inorganic Chemistry},
issn = {0020-1669},
number = 17,
volume = 49,
place = {United States},
year = {2010},
month = {9}
}