Probing the role of pre-aggregation in rhodamine-based organic photocatalysis: a combined computational and single-molecule approach
Final Report Abstract
A photon of blue light carries sufficient energy to cleave a covalent bond of a molecule, given a suitable catalyst to enable the reaction between substrate compound and reactant photon. Remarkably, organic dye molecules themselves can perform such an operation by consecutive photoelectron transfer: one photon is absorbed by the dye to form a radical state, and a second photon excites the radical to enable transfer of an electron to a substrate compound, breaking a bond. We set out to investigate this process in a model system comprising a rhodamine dye molecule and a bromine benzonitrile acceptor molecule, to explore the effect of changing reaction conditions: photon fluence and substrate concentration. Preliminary experiments, performed on the level of one single dye molecule, appeared to suggest that substrate and photocatalyst pre-associate so that the actual reaction is not limited by molecular diffusion in solution. We therefore also aimed to examine the energetics of such pre-association by excitedstate electronic structure calculations. Adapting existing theory to this problem required substantial efforts on testing and improving the computational methods, but ultimately succeeded. Although this joint theory-experiment project was initially triggered by experiments, we found further exploration of the parameter space available surprisingly challenging. During the course of the project we therefore adapted the experimental aims to explore both some fundamental aspects of photon correlation measurements on the single-molecule level as well as developing new non-linear optical pump-probe schemes, which were also applied to molecule-like twodimensional semiconductors.
Publications
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Accurate Molecular Geometries in Complex Excited-State Potential Energy Surfaces from Time-Dependent Density Functional Theory. Journal of Chemical Theory and Computation, 17(1), 357-366.
Kretz, Bernhard & Egger, David A.
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Excitation Energy Transfer between bodipy Dyes in a Symmetric Molecular Excitonic Seesaw. The Journal of Physical Chemistry A, 125(38), 8404-8416.
Freixas, Victor M.; Wilhelm, Philipp; Nelson, Tammie; Hinderer, Florian; Höger, Sigurd; Tretiak, Sergei; Lupton, John M. & Fernandez-Alberti, Sebastian
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Expanded all-phenylene molecular spoked wheels: cutouts of graphenylene-3. Organic Chemistry Frontiers, 8(18), 4980-4985.
Sterzenbach, Christopher; Keller, Tristan J.; Kraus, Daniel; Lupton, John M.; Jester, Stefan-S. & Höger, Sigurd
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How Blinking Affects Photon Correlations in Multichromophoric Nanoparticles. ACS Nano, 15(11), 18037-18047.
Schröder, Tim; Bange, Sebastian; Schedlbauer, Jakob; Steiner, Florian; Lupton, John M.; Tinnefeld, Philip & Vogelsang, Jan
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Unexpectedly flexible graphene nanoribbons with a polyacene ladder skeleton. Journal of Materials Chemistry C, 9(45), 16208-16216.
Unruh, Marvin T.; Scherf, Ullrich; Bahmann, Hilke; Rodrigues, Ana Clara B.; Cunha, Carla; Seixas, de Melo J. Sérgio; Schedlbauer, Jakob & Lupton, John M.
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Accurate non-adiabatic couplings from optimally tuned range-separated hybrid functionals. The Journal of Chemical Physics, 157(10).
Kretz, Bernhard & Egger, David A.
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Excitonic resonances control the temporal dynamics of nonlinear optical wave mixing in monolayer semiconductors. Nature Photonics, 16(11), 777-783.
Bauer, Jonas M.; Chen, Lijue; Wilhelm, Philipp; Watanabe, Kenji; Taniguchi, Takashi; Bange, Sebastian; Lupton, John M. & Lin, Kai-Qiang
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Role of Preaggregation in Single-Molecule Photoredox Catalysis. The Journal of Physical Chemistry C, 127(24), 11666-11671.
Kretz, Bernhard; Wutz, Philipp; Schedlbauer, Jakob; Vogelsang, Jan; Lupton, John M. & Egger, David A.
