Abstract
The reduction of carbon dioxide to chemical fuels such as carbon monoxide is an important challenge in the field of renewable energy conversion. Given the thermodynamic stability of carbon dioxide, it is difficult to efficiently activate this substrate in a selective fashion and the development of new electrocatalysts for CO2 reduction is of prime importance. To this end, we have prepared and studied a new fac-ReI(CO)3 complex supported by a bipyridine ligand containing ancillary BODIPY moieties ([Re(BB2)(CO)3Cl]). Voltammetry experiments revealed that this system displays a rich redox chemistry under N2, as [Re(BB2)(CO) 3Cl] can be reduced by up to four electrons at modest potentials. These redox events have been characterized as the ReI/0 couple, and three ligand based reductions - two of which are localized on the BODIPY units. The ability of the BB2 ligand to serve as a non-innocent redox reservoir is manifest in an enhanced electrocatalysis with CO2 as compared to an unsubstituted Re-bipyridine complex lacking BODIPY units ([Re(bpy)(CO) 3Cl]). The second order rate constant for reduction of CO2 by [Re(BB2)(CO)3Cl] was measured to be k = 3400 M-1 s-1 at an applied potential of -2.0 V versus SCE, which is roughly three times greater than the corresponding unsubstituted Re-bipyridine homologue. Photophysical and photochemical studies were also carried out to determine if [Re(BB2)(CO)3Cl] was a competent platform for CO 2 reduction using visible light. These experiments showed that this complex supports unusual excited state dynamics that precludes efficient CO 2 reduction and are distinct from those that are typically observed for fac-ReI(CO)3 complexes.
Original language | English |
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Pages (from-to) | 149-157 |
Number of pages | 9 |
Journal | Catalysis Today |
Volume | 225 |
DOIs | |
State | Published - Apr 15 2014 |
Funding
Research reported in this publication was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under Grant Number P20GM103541 . J.R. was supported through a DuPont Young Professor award. J.R. also thanks the University of Delaware Research Foundation and the donors of the American Chemical Society's Petroleum Research Fund for financial support. D.A.L. was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory , managed by UT-Battelle, LLC, for the U.S. Department of Energy. Y.-Z.M. was sponsored by the Division of Chemical Sciences,Geosciences, and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy. The authors thank the Ohio Supercomputer Center for support. NMR and other data were acquired at UD using instrumentation obtained with assistance from the NSF and NIH (NSF-MIR 0421224, NSF-MIR 1048367, NSF-CRIF MU CHE-0840401 and CHE-0541775, NIH P20 RR017716).
Keywords
- BODIPY
- Carbon dioxide
- Catalysis
- Electrochemistry
- Photochemistry
- Rhenium bipyridine derivatives