Direct Observation of the Photoreduction Products of Mn(NDI-bpy)(CO) 3 X CO 2 Reduction Catalysts Using Femtosecond Transient IR Spectroscopy

Jose F. Martinez, Nathan T. La Porte, Ryan M. Young, Alessandro Sinopoli, Muhammad Sohail, Michael R. Wasielewski

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Abstract

The electrochemical reduction of the Mn(bpy)(CO) 3 X CO 2 reduction catalyst is thought to proceed by the initial reduction of Mn I to Mn 0 . 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) 3 X, where X = Br, CH 3 CN, 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) 3 X → Mn(NDI-bpy •- )(CO) 3 X is observed, whereas in the complex where NDI •- is attached to the 6-position of bipyridine, the reaction sequence Mn( 2∗ NDI •- -bpy)(CO) 3 X → Mn(NDI-bpy •- )(CO) 3 X → Mn 0 (NDI-bpy)(CO) 3 is observed. Moreover, in the complexes with an NDI •- bound to the 6-position of bipyridine, Mn 0 (NDI-bpy)(CO) 3 exhibits a lifetime that is ∼10 5 times longer than those in complexes with an NDI •- bound at the four- or five-position of the bipyridine.

Original languageEnglish
Pages (from-to)6416-6426
Number of pages11
JournalJournal of Physical Chemistry C
Volume123
Issue number11
DOIs
Publication statusPublished - 21 Mar 2019

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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