Scientific Results

Red Thermally Activated Delayed Fluorescence and the Intersystem Crossing Mechanisms in Compact Naphthalimide-Phenothiazine Electron Donor/Acceptor Dyads

Year: 2019

Authors: Tang GL., Sukhanov AA., Zhao JZ., Yang WB., Wang ZJ., Liu QY., Voronkova VK., Di Donato M., Escudero D., Jacquemin D.

Autors Affiliation: Dalian Univ Technol, Sch Chem Engn, State Key Lab Fine Chem, Dalian 116024, Peoples R China; RAS, Zavoisky Phys Tech Inst, FRC Kazan Sci Ctr, Kazan 420029, Russia; Xinjiang Univ, Sch Chem & Chem Engn, Minist Educ, Inst Appl Chem, Urumqi 830046, Peoples R China; Xinjiang Univ, Key Lab Energy Mat Chem, Minist Educ, Inst Appl Chem, Urumqi 830046, Peoples R China; Shandong Univ Sci & Technol, Coll Chem & Environm Engn, Qingdao 266590, Shandong, Peoples R China; European Labor Nonlinear Spect, Via N Carrara 1, I-50019 Sesto Fiorentino, Italy; Ist Nazl Ott Largo Enrico, INO, Fermi 6, I-50125 Florence, Italy; Katholieke Univ Leuven, Dept Chem, Celestijnenlaan 200F, B-3001 Leuven, Belgium; Univ Nantes, Lab CEISAM, CNRS, UMR 6230, 2 Rue Houssiniere, F-44322 Nantes 3, France

Abstract: Controlling the electronic coupling between electron donor and acceptor subunits in a dyad is pivotal for the development of novel organic materials, for instance, thermally activated delayed fluorescence (TADF) materials and triplet photosensitizers. Herein, we prepared two compact electron donor/acceptor dyads based on phenothiazine (PTZ) and naphthalimide (NI) with different conformation restrictions induced by the C-N (NI-N-PTZ) or C-C (NI-C-PTZ) linkers. The effect of electronic coupling (matrix elements, V-DA) on the photophysical properties, especially the intersystem crossing (ISC) and the TADF, were investigated. NI-C-PTZ shows stronger ground-state electronic coupling (V-DA = 2548 cm(-1)) compared to NI-N-PTZ (V-DA = 870 cm(-1)). TADF was observed only for NI-N-PTZ due to its smaller electronic coupling. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy indicated the presence two triplet excited states and three ISC mechanisms in NI-N-PTZ with different electron spin polarizations (ESP): radical pair ISC (RP-ISC) and spin-orbital charge transfer ISC (SOCT-ISC) for one triplet state, and spin-orbital coupling ISC (SO-ISC) for another. Moreover, for the second one, an inversion of the electron spin polarization (ESP) was observed at 0.5-1.1 mu s delay time. NI-N-PTZ represents a rare example for compact electron donor/acceptor dyad showing TADF emission in the red spectral region.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY C

Volume: 124 (50)      Pages from: 30171  to: 30186

KeyWords: ANNIHILATION UP-CONVERSION; TRIPLET EXCITED-STATE; INTRAMOLECULAR CHARGE-TRANSFER; TIME-RESOLVED EPR; SINGLET OXYGEN; ENERGY-TRANSFER; PARAMAGNETIC-RES; METAL-COMPLEXES; PI-A; DONOR
DOI: 10.1021/acs.jpcc.9b09335

Citations: 21
data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2021-11-21
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