Molecular Strategies for Directional Photoinduced Charge Transfer and Charge Accumulation

Event time: 
May 1, 2023 - 4:00pm to 5:30pm
Sterling Chemistry Laboratory (SCL) See map
Event description: 

Location: SCL 160

Join Yale Chemistry for an Inorganic Chemistry Seminar with Karen Mulfort, Chemist, U.S. Department of Energy’s (DOE) Argonne National Laboratory.

Abstract: This talk will describe our group’s recent work to understand the directionality of photoinduced charge transfer and charge separation following visible excitation of heteroleptic Cu(I)bis(phenanthroline) complexes. Intramolecular metal-to-ligand charge transfer (MLCT) was investigated by installation of electron-donating or –withdrawing groups on only one of the coordinating ligands. Using UV-Vis spectroscopy, cyclic voltammetry, and electronic structure calculations we found that MLCT is localized on only one ligand, which has profound implications for the excited-state lifetime.

[1] Careful analysis of the kinetics of intramolecular charge separation in structural isomers of a Cu(I)bis(phen)—naphthalene diimide dyad reveals dramatically different kinetics depending on the location of the electron acceptor and further confirms the directionality of initial MLCT.

[2] Intermolecular charge separation from a water-soluble Cu(I)bis(phen) to methyl viologen is enabled by electrostatic interactions between the photosensitizer and electron acceptor, proceeds with near quantitative quantum efficiency, and persists for several microseconds.

[3] Finally, the kinetics of interfacial charge injection from heteroleptic Cu(I)bis(phen) complexes into TiO2 nanoparticle thin films are dictated by the orientation of the anchoring ligand with respect to the Cu(I) center.

[4] This work provides a set of design principles for directional charge transfer from molecular photosensitizers based on earth-abundant elements, and will be used to efficiently design pathways for connecting with catalysts or electrodes, and integration into systems for light-driven catalysis.

[1] L. Wang, Z.-L. Xie, B. T. Phelan, V. M. Lynch, L. X. Chen, K. L. Mulfort, 2023, submitted.
[2] D. Hayes, L. Kohler, L. X. Chen, K. L. Mulfort, J Phys Chem Lett 2018, 9, 2070-2076.
[3] A. M. Potocny, B. T. Phelan, M. W. Mara, E. A. Sprague-Klein, D. M. Tiede, L. X. Chen, K. L. Mulfort, Inorg. Chem. 2022, 61, 19119-19133.
[4] K. Dey, B. T. Phelan, L. Wang, L. X. Chen, K. L. Mulfort, 2023, in preparation.

About: Karen Mulfort is a Chemist and Group Leader of the Solar Energy Conversion Group at Argonne National Laboratory. Her current research program focuses on the design and discovery of molecular architectures for artificial photosynthesis, and understanding the physical, chemical, and electronic factors that contribute to effective conversion of light energy to chemical energy. Her work is focused largely on utilizing earth-abundant elements and she is particularly interested in discovering the impact of outer coordination sphere and microenvironment on molecular photochemistry and photocatalysis. Karen was a Director’s Postdoctoral Fellow at Argonne with David Tiede, after earning her Ph.D. in Materials Chemistry from Northwestern University with Joseph Hupp in 2008.

This seminar is generously sponsored by the Mrs. Hepsa Ely Silliman Memorial Fund