A time-resolved electron spin resonance study of the triplet states of quinoline, isoquinoline, their protonated cations and naphthalene

Yagi, Mikio; Komura, Akinori; Higuchi, Jiro

doi:10.1016/0009-2614(88)87256-7

Cited by 11 publications

(1 citation statement)

References 25 publications

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“…ESP is due to the selective population of T X and T Y eigenstates, with in-plane orientation of the ZFS dipolar principal components. Similar population patterns, which leave the T Z state empty (with principal direction of the ZFS component perpendicular to the π-plane), are typical SO-ISC of oblate π-systems, like for the parent naphthalene molecule, anthracene, or for the tetracarboxy-diimide derivative of perylene; indeed, all of their TREPR spectra are characterized by the eee / aaa pattern.…”

Section: Resultsmentioning

confidence: 77%

Spin–Orbit Charge-Transfer Intersystem Crossing of Compact Naphthalenediimide-Carbazole Electron-Donor–Acceptor Triads

et al. 2021

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Compact electron donor−acceptor triads based on carbazole (Cz) and naphthalenediimide (NDI) were prepared to study the spin−orbit charge-transfer intersystem crossing (SOCT-ISC). By variation of the molecular conformation and electron-donating ability of the carbazole moieties, the electronic coupling between the two units was tuned, and as a result charge-transfer (CT) absorption bands with different magnitudes were observed (ε = 4000−18 000 M −1 cm −1 ). Interestingly, the triads with NDI attached at the 3-C position or with a phenyl spacer at the N position of the Cz moiety, thermally activated delayed fluorescence (TADF) was observed. Femtosecond transient absorption (fs-TA) spectroscopy indicated fast electron transfer (0.8−1.5 ps) from the Cz to NDI unit, followed by population of the triplet state (150−600 ps). Long-lived triplet states (up to τ T = 45−50 μs) were observed for the triads. The solvent-polarity-dependent singlet-oxygen quantum yield (Φ Δ ) is 0−26%. Timeresolved electron paramagnetic resonance (TREPR) spectral study of TADF molecules indicated the presence of the 3 CT state for NDI-Cz-Ph (zero-field-splitting parameter D = 21 G) and an 3 LE state for NDI-Ph-Cz (D = 586 G). The triads were used as triplet photosensitizers in triplet−triplet annihilation upconversion by excitation into the CT absorption band; the upconversion quantum yield was Φ UC = 8.2%, and there was a large anti-Stokes shift of 0.55 eV. Spatially confined photoexcitation is achieved with the upconversion using focusing laser beam excitation, and not the normally used collimated laser beam, i.e., the upconversion was only observed at the focal point of the laser beam. Photo-driven intermolecular electron transfer was demonstrated with reversible formation of the NDI −• radical anion in the presence of the sacrificial electron donor triethanolamine.

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Section: Resultsmentioning

confidence: 77%