Charge Separation/Recombination, Intersystem Crossing, and Unusually Slow Intramolecular Triplet-Triplet Energy Transfer in Naphthalenediimide-Anthracene Compact Energy Donor-Acceptor Dyads

Xi Chen; Andrey A Sukhanov; Maria Taddei; Bernhard Dick; Jianzhang Zhao; Violeta K Voronkova; Mariangela Di Donato

doi:10.1021/acs.jpclett.2c02118

Charge Separation/Recombination, Intersystem Crossing, and Unusually Slow Intramolecular Triplet-Triplet Energy Transfer in Naphthalenediimide-Anthracene Compact Energy Donor-Acceptor Dyads

J Phys Chem Lett. 2022 Sep 22;13(37):8740-8748. doi: 10.1021/acs.jpclett.2c02118. Epub 2022 Sep 13.

Authors

Xi Chen¹, Andrey A Sukhanov², Maria Taddei³, Bernhard Dick⁴, Jianzhang Zhao^{1

5}, Violeta K Voronkova², Mariangela Di Donato^{3

6}

Affiliations

¹ State Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart Materials Oriented Chemical Engineering, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian 116024, P. R. China.
² Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS, Kazan 420029, Russia.
³ LENS (European Laboratory for Non-Linear Spectroscopy), Via N. Carrara 1, 50019 Sesto Fiorentino (FI), Italy.
⁴ Lehrstuhl für Physikalische Chemie, Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Regensburg 93053, Germany.
⁵ State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University, Urumqi 830046, P. R. China.
⁶ ICCOM-CNR, via Madonna del Piano 10-12, 50019 Sesto Fiorentino, Italy.

PMID: 36098552
DOI: 10.1021/acs.jpclett.2c02118

Abstract

Three anthracene (An)-naphthalenediimide (NDI) compact electron donor-acceptor dyads were prepared. Femtosecond transient absorption (fs-TA) spectra show fast charge separation (ca. 0.9-1.7 ps) and relatively slow charge recombination (ca. 8-565 ps) upon photoexcitation; moreover, the ³An state was observed for 9-An-NDI, whereas the final state is ³NDI for both 9-An-Ph-NDI and 2-An-Ph-NDI, which have an intervening phenyl linker between the An and NDI units. Nanosecond transient absorption (ns-TA) spectra indicate that the lowest triplet state of all the dyads is ³An, with triplet lifetimes of 139-354 μs. An unusually slow intramolecular triplet-triplet energy transfer (TTET) was observed for 9-An-Ph-NDI and 2-An-Ph-NDI (32-85 ns). Time-resolved electron paramagnetic resonance (TREPR) spectroscopy confirms that the intersystem crossing (ISC) mechanism is spin orbit charge transfer ISC (SOCT-ISC) for all the dyads; for 9-An-NDI, only the ³An state was observed, while for the other two dyads, both ³NDI and ³An states were observed, with their relative population changing with increasing delay time, which supports TTET.