TY - JOUR
T1 - Direct Observation of the Photoreduction Products of Mn(NDI-bpy)(CO)3X CO2 Reduction Catalysts Using Femtosecond Transient IR Spectroscopy
AU - Martinez, Jose F.
AU - La Porte, Nathan T.
AU - Young, Ryan M.
AU - Sinopoli, Alessandro
AU - Sohail, Muhammad
AU - Wasielewski, Michael R.
N1 - Publisher Copyright:
© Copyright 2019 American Chemical Society.
PY - 2019/3/21
Y1 - 2019/3/21
N2 - The electrochemical reduction of the Mn(bpy)(CO)3X CO2 reduction catalyst is thought to proceed by the initial reduction of MnI to Mn0. We have covalently attached a naphthalenediimide radical anion (NDI•-) chromophore to the 4-, 5-, or 6-position of the bpy via a phenyl bridge to produce Mn(NDI•--bpy)(CO)3X, where X = Br, CH3CN, or DMF, and have used femtosecond and nanosecond transient IR spectroscopy to directly observe the intermediates produced by two electron-transfer reactions following selective photoexcitation of NDI•- to its lowest excited doublet state, 2∗NDI•-. In complexes where NDI•- is attached at the 4- or 5-position of bipyridine, only the reaction Mn(2∗NDI•--bpy)(CO)3X → Mn(NDI-bpy•-)(CO)3X is observed, whereas in the complex where NDI•- is attached to the 6-position of bipyridine, the reaction sequence Mn(2∗NDI•--bpy)(CO)3X → Mn(NDI-bpy•-)(CO)3X → Mn0(NDI-bpy)(CO)3 is observed. Moreover, in the complexes with an NDI•- bound to the 6-position of bipyridine, Mn0(NDI-bpy)(CO)3 exhibits a lifetime that is ∼105 times longer than those in complexes with an NDI•- bound at the four- or five-position of the bipyridine.
AB - The electrochemical reduction of the Mn(bpy)(CO)3X CO2 reduction catalyst is thought to proceed by the initial reduction of MnI to Mn0. We have covalently attached a naphthalenediimide radical anion (NDI•-) chromophore to the 4-, 5-, or 6-position of the bpy via a phenyl bridge to produce Mn(NDI•--bpy)(CO)3X, where X = Br, CH3CN, or DMF, and have used femtosecond and nanosecond transient IR spectroscopy to directly observe the intermediates produced by two electron-transfer reactions following selective photoexcitation of NDI•- to its lowest excited doublet state, 2∗NDI•-. In complexes where NDI•- is attached at the 4- or 5-position of bipyridine, only the reaction Mn(2∗NDI•--bpy)(CO)3X → Mn(NDI-bpy•-)(CO)3X is observed, whereas in the complex where NDI•- is attached to the 6-position of bipyridine, the reaction sequence Mn(2∗NDI•--bpy)(CO)3X → Mn(NDI-bpy•-)(CO)3X → Mn0(NDI-bpy)(CO)3 is observed. Moreover, in the complexes with an NDI•- bound to the 6-position of bipyridine, Mn0(NDI-bpy)(CO)3 exhibits a lifetime that is ∼105 times longer than those in complexes with an NDI•- bound at the four- or five-position of the bipyridine.
UR - http://www.scopus.com/inward/record.url?scp=85063324133&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.9b00138
DO - 10.1021/acs.jpcc.9b00138
M3 - Article
AN - SCOPUS:85063324133
SN - 1932-7447
VL - 123
SP - 6416
EP - 6426
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 11
ER -