1. Excited-State Charge Distribution of a Donor-π-Acceptor Zn Porphyrin Probed by N K-Edge Transient Absorption Spectroscopy
- Author
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Gema de la Torre, Amy A. Cordones, Ioannis Zegkinoglou, Robert W. Schoenlein, C. Das Pemmaraju, F. J. Himpsel, Jae Hyuk Lee, and Maria-Eleni Ragoussi
- Subjects
Materials science ,Absorption spectroscopy ,02 engineering and technology ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Triphenylamine ,01 natural sciences ,Acceptor ,Porphyrin ,0104 chemical sciences ,Crystallography ,chemistry.chemical_compound ,chemistry ,Excited state ,General Materials Science ,Physical and Theoretical Chemistry ,Absorption (chemistry) ,0210 nano-technology ,Spectroscopy - Abstract
Zinc porphyrin solar cell dyes with donor-π-acceptor architectures combine light absorber (π), electron-donor, and electron-acceptor moieties inside a single molecule with atomic precision. The donor-π-acceptor design promotes the separation of charge carriers following optical excitation. Here, we probe the excited-state electronic structure within such molecules by combining time-resolved X-ray absorption spectroscopy at the N K-edge with first-principles time-dependent density functional theory (TD-DFT) calculations. Customized Zn porphyrins with strong-donor triphenylamine groups or weak-donor tri-tert-butylbenzene groups were synthesized. Energetically well-separated N K-edge absorption features simultaneously probe the excited-state electronic structure from the perspectives of the macrocycle and triphenylamine N atoms. New absorption transitions between the macrocycle N atoms and the excited-state HOMO vacancy are observed, and the triphenylamine associated absorption feature blue-shifts, consistent with partial oxidation of the donor groups in the excited state.
- Published
- 2021