jp8b12264_si_002.cif (16.19 kB)
Effect of Electronic Coupling on Electron Transfer Rates from Photoexcited Naphthalenediimide Radical Anion to Re(bpy)(CO)3X
dataset
posted on 2019-03-06, 00:00 authored by Jose F. Martinez, Nathan T. La Porte, Subhajyoti Chaudhuri, Alessandro Sinopoli, Youn Jue Bae, Muhammad Sohail, Victor S. Batista, Michael R. WasielewskiThe
electron transfer rate between a donor and an acceptor depends on the free energy change for the
reaction as well as differences in structure and electronic coupling
between the initial and final states. Selective excitation of a naphthalenediimide
radical anion (NDI•–) covalently linked at
the 4-, 5-, or 6-positions of the bipyridine (bpy) in the Re(bpy)(CO)3X (X = Cl or pyridine) carbon dioxide reduction catalyst results
in electron transfer from 2*NDI•– to Re(bpy)(CO)3X to form Re(bpy•–)(CO)3X, the first intermediate in the photocatalytic
reduction of CO2. Femtosecond UV/vis, near-IR, and mid-IR
spectroscopy on these constitutional isomers and a set of appropriate
reference molecules show that systematically varying the electronic
coupling as well as the reaction free energy increases the lifetime
of Re(bpy•–)(CO)3X by an order
of magnitude when the NDI chromophore is attached to the 6-position
of bpy. NMR and X-ray structural studies along with computational
modeling are used to identify the conformation of Re(6-NDI-bpy)(CO)3X responsible for these favorable changes. Extending the lifetime
of the reduced complex in the covalent photosensitizer–catalyst
assembly is a critical requirement for the photocatalytic CO2 reduction and artificial photosynthesis.