Reassignment of the Near-Infrared Absorption of Dioxidized Rare-Earth Porphyrin Double-Decker Complexes: Identification of a Nearly Dark Lowest Excited State
- 1Department of Chemistry, Graduate School of Science, The University of Osaka, 1-1 Machikaneyama, Toyonaka, Osaka, Japan, 560-0043
- 2Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI)
- 3The University of Osaka
Abstract
The intense near-infrared band (700–1250 nm) of dioxidized porphyrin double-decker complexes, characterized by a metal ion sandwiched between two porphyrinato ligands bearing two holes in total, has been assigned to the HOMO→LUMO transition for three decades. Herein, we demonstrate that this band does not correspond to the lowest excited state. In the spectra of [Y(oep) 2 ] + and [Tb(oep) 2 ] + (oep = octaethylporphyrinato), we observed a weak band near 1430 nm, with 2–3% of the absorbance of the intense band (at 812 nm and 830 nm) and a much smaller dependence on the metal. Time-dependent density functional theory calculations with an optimally tuned functional assigned the weak and intense bands to S 1 and S 3 , respectively, i.e., a configuration-interaction pair of the HOMO→LUMO and HOMO−1→LUMO excitations. As observed in crystal structures reported earlier, the two rings are twisted by 30–36°, which lowers the symmetry from D 4d (45°) to D 4 . The weak band S 1 is symmetry-forbidden in D 4d and owes its low intensity to this twist. The calculated slope of S 3 against the ionic radius was within 3% of the experimental value, whereas S 1 was nearly independent of the metal. Therefore, the lowest excited states of these strongly coupled π dimers are nearly dark.
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BibTeX
@misc{imanaka2026reassignment,
title = {{Reassignment of the Near-Infrared Absorption of Dioxidized Rare-Earth Porphyrin Double-Decker Complexes: Identification of a Nearly Dark Lowest Excited State}},
author = {Wataru Imanaka and Ken-ichi Yamashita},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010956/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010956/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Reassignment of the Near-Infrared Absorption of Dioxidized Rare-Earth Porphyrin Double-Decker Complexes: Identification of a Nearly Dark Lowest Excited State
AU - Wataru Imanaka
AU - Ken-ichi Yamashita
PY - 2026
DA - 2026/10/23
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010956/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010956/v1
AB - The intense near-infrared band (700–1250 nm) of dioxidized porphyrin double-decker complexes, characterized by a metal ion sandwiched between two porphyrinato ligands bearing two holes in total, has been assigned to the HOMO→LUMO transition for three decades. Herein, we demonstrate that this band does not correspond to the lowest excited state. In the spectra of [Y(oep) 2 ] + and [Tb(oep) 2 ] + (oep = octaethylporphyrinato), we observed a weak band near 1430 nm, with 2–3% of the absorbance of the intense band (at 812 nm and 830 nm) and a much smaller dependence on the metal. Time-dependent density functional theory calculations with an optimally tuned functional assigned the weak and intense bands to S 1 and S 3 , respectively, i.e., a configuration-interaction pair of the HOMO→LUMO and HOMO−1→LUMO excitations. As observed in crystal structures reported earlier, the two rings are twisted by 30–36°, which lowers the symmetry from D 4d (45°) to D 4 . The weak band S 1 is symmetry-forbidden in D 4d and owes its low intensity to this twist. The calculated slope of S 3 against the ionic radius was within 3% of the experimental value, whereas S 1 was nearly independent of the metal. Therefore, the lowest excited states of these strongly coupled π dimers are nearly dark.
ER -