TY - JOUR
T1 - Excitation Energy Transfer and Exchange-Mediated Quartet State Formation in Porphyrin-Trityl Systems
AU - Nolden, Oliver
AU - Fleck, Nico
AU - Lorenzo, Emmaline R.
AU - Wasielewski, Michael R.
AU - Schiemann, Olav
AU - Gilch, Peter
AU - Richert, Sabine
N1 - Funding Information:
This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project number 417643975 (S.R.) and GRK 2482 ′ModISC′, project B2 (P.G.), as well as the University of Freiburg through project number 2100297101 (Innovationsfonds Forschung) and the U.S. National Science Foundation under grant no. CHE‐1900422 (M.R.W.). The authors acknowledge support by the state of Baden‐Württemberg through bwHPC and the German Research Foundation (DFG) through grant number INST 40/467‐1 FUGG (JUSTUS cluster) and thank the SIBW/DFG for financing EPR instrumentation that is operated within the MagRes Center of the University of Freiburg (grant no. INST 39/928‐1 FUGG). E.R.L. was supported by a U.S. National Science Foundation Graduate Research Fellowship (DGE‐1842165). S.R. would like to express her gratitude to Prof. S. Weber (University of Freiburg, Germany) for providing her access to his EPR instrumentation and equipment, and to Prof. A. van der Est (Brock University, Canada) for fruitful discussions. Open access funding enabled and organized by Projekt DEAL.
PY - 2020
Y1 - 2020
N2 - Photogenerated multi-spin systems hold great promise for a range of technological applications in various fields, including molecular spintronics and artificial photosynthesis. However, the further development of these applications, via targeted design of materials with specific magnetic properties, currently still suffers from a lack of understanding of the factors influencing the underlying excited state dynamics and mechanisms on a molecular level. In particular, systematic studies, making use of different techniques to obtain complementary information, are largely missing. This work investigates the photophysics and magnetic properties of a series of three covalently-linked porphyrin-trityl compounds, bridged by a phenyl spacer. By combining the results from femtosecond transient absorption and electron paramagnetic resonance spectroscopies, we determine the efficiencies of the competing excited state reaction pathways and characterise the magnetic properties of the individual spin states, formed by the interaction between the chromophore triplet and the stable radical. The differences observed for the three investigated compounds are rationalised in the context of available theoretical models and the implications of the results of this study for the design of a molecular system with an improved intersystem crossing efficiency are discussed.
AB - Photogenerated multi-spin systems hold great promise for a range of technological applications in various fields, including molecular spintronics and artificial photosynthesis. However, the further development of these applications, via targeted design of materials with specific magnetic properties, currently still suffers from a lack of understanding of the factors influencing the underlying excited state dynamics and mechanisms on a molecular level. In particular, systematic studies, making use of different techniques to obtain complementary information, are largely missing. This work investigates the photophysics and magnetic properties of a series of three covalently-linked porphyrin-trityl compounds, bridged by a phenyl spacer. By combining the results from femtosecond transient absorption and electron paramagnetic resonance spectroscopies, we determine the efficiencies of the competing excited state reaction pathways and characterise the magnetic properties of the individual spin states, formed by the interaction between the chromophore triplet and the stable radical. The differences observed for the three investigated compounds are rationalised in the context of available theoretical models and the implications of the results of this study for the design of a molecular system with an improved intersystem crossing efficiency are discussed.
KW - enhanced intersystem crossing
KW - excitation energy transfer
KW - excited multi-spin systems
KW - quartet state formation
KW - transient EPR spectroscopy
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U2 - 10.1002/chem.202002805
DO - 10.1002/chem.202002805
M3 - Article
AN - SCOPUS:85090786293
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
ER -