Photogeneration of Hydride Donors and Their Use Toward CO2 Reduction Page: 3 of 7
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
B N L-90201-2009-CP
PHOTOGENERATION OF HYDRIDE DONORS AND THEIR USE TOWARD CO2
Etsuko Fujita, James T. Muckerman, Dmitry E. Polyansky
Brookhaven National Laboratory
Upton, NY 11973-5000
Despite substantial effort, no one has succeeded in efficiently producing methanol from CO2
using homogeneous photocatalytic systems. We are pursuing reaction schemes based on a
sequence of hydride-ion transfers to carry out stepwise reduction of CO2 to methanol. We are
using hydride-ion transfer from photoproduced C-H bonds in metal complexes with bio-inspired
ligands (i.e., NADH-like ligands) that are known to store one proton and two electrons.
1. Photogeneration of Hydride Donors: We have shown that a polypyridylruthenium complex
with an NAD+/NADH model ligand, [Ru(bpy)2(pbn)]2+ (2+, bpy = 2,2'-bipyridine, pbn = 2-(2-
N -2 zH 2. pyridyl)-benzo[b]-1,5-naphthyri-dine) in a
N N wet CH3CN/amine solution, undergoes
NRu] EN/HN H H proton-coupled two-electron reduction to
1.5 2 [1.HH]2+ give [Ru(bpy)2(pbnH)]2+ ([1HH]2+
After Irradiation pbnHH = 5,10-dihydro-2-(2-pyridyl)-
- benzo[b]-1,5-naphthyridine) upon irradiation
. Before Irradiation of visible light (300-600 nm). When
-~ triethylamine was used as a sacrificial
electron donor, the quantum yield for
U 40 500 6o goo soo [1-HH]2+ formation is 0.21 at 355 nm. This
Wavelength, nm result opens a new door to photoinduced
catalytic hydride-transfer reactions !
2. Kinetic and Mechanistic Investigation of Hydride Donor Generation by Pulse Radiolysis:
Using the pulse radiolysis technique, we determined the mechanism of formation of [1-HH]2+ in
water. Protonation of the one-electron- H
reduced species  takes place below N N - N N H N 2
pH 11 to form  (pKa -11). Species  -NtRu 2+ I -NfRI] 2 pa=1. N' u H 3
disproportionates through a 7-stacked 3+HI 3
dimer at low pH (see below), and the 2]. k=1.2X1O M s 22X1M
dimer dissociates to yield 2+ and H [Ru]-N 4+
[1HH]2+. The cross reaction between i 'N N 2+
 and  yields the same final -NjRJu H H 2 N-Hu
products at high pH, probably by [1-HH]2+
forming a N-H N hydrogen bonding interaction between the two species, the transfer of an
electron to , which subsequently acquires a proton.
3. Stereo-Specific Photochemical Formation of a C-H Hydride: Our photolysis experiments
with D20 and H20 solutions containing 2+/CH3CN/triethanolamine produced [1-DD]2+ (m/z
337.5838) and [1-HH]2+ (m/z 336.5725), respectively. 1H and 13C NMR indicate that stereo-
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Fujita,E.; Muckerman, J.T. & Polyansky, D.E. Photogeneration of Hydride Donors and Their Use Toward CO2 Reduction, article, June 7, 2009; United States. (digital.library.unt.edu/ark:/67531/metadc932077/m1/3/: accessed December 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.