Intersystem crossing, phosphorescence, and spin-orbit coupling. Two contrasting Cu(I)-TADF dimers investigated by milli- to micro-second phosphorescence, femto-second fluorescence, and theoretical calculations
Yersin H. Czerwieniec R. Monkowius U. Ramazanov R. Valiev R. Shafikov M.Z. Kwok W.-M. Ma C.
1 March 2023Elsevier B.V.
Coordination Chemistry Reviews
2023#478
Applying femto-second time-resolved spectroscopy, we study intersystem crossing times τ(ISC) of two Cu(I) dimers, Cu2Cl2(dppb)2 1 (dppb = 1,2-bis-diphenylphosphino)benzene) and Cu2Cl2(N^P)2 2 (N^P = 2-(diphenylphosphino)-6-methylpyridine) used as powders. τ(ISC) varies by more than one order of magnitude from 39 ps (1) to 3.7 ps (2). A similar trend is displayed in the radiative phosphorescence decay time τr(T1) and the zero-field splitting (ZFS) amounting to τr(T1) = 4.2 ms and ZFS < 1 cm−1 (0.1 meV) for 1 and 45 µs and 15 cm−1 (1.9 meV) for 2. Simple quantum mechanical considerations and TD-DFT calculations allow us to correlate these different photophysical mechanisms. This is related to the efficiency of spin–orbit coupling (SOC), in particular with respect to the triplet state T1. Presumably, inter-metallic interactions, occurring in 2, are the source of the much more efficient SOC between T1 and neighboring states, thus, providing a relation between structure and photophysical properties. Accordingly, easily accessible phosphorescence data or even just structure data might already help to predict trends in ISC, at least for Cu(I) dimers. As for TADF emitters applied in OLEDs, τ(ISC) should be as fast as possible, the presented discussions might help to better understand ISC processes, in particular, with respect of speeding them up.
Copper(I) dimers , Femtosecond spectroscopy , Fluorescence , Intersystem crossing , Organic light emitting diodes (OLEDs) , Phosphorescence , Spin-orbit coupling , Thermally activated delayed fluorescence (TADF)
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Institut für Physikalische Chemie, University of Regensburg, Regensburg, 93053, Germany
School of Education, Johannes Kepler University Linz, Linz, A-4040, Austria
Department of Chemistry, University of Helsinki, Helsinki, FI-00014, Finland
Al Farabi Kazakh National University, Almaty, Kazakhstan
Ural Federal University, Mira 19, Ekaterinburg, 620002, Russian Federation
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Kowloon, 999077, Hong Kong
College of Chemistry and Environmental Engineering, Shenzhen University, Guangdong, Shenzhen, 518071, China
Institut für Physikalische Chemie
School of Education
Department of Chemistry
Al Farabi Kazakh National University
Ural Federal University
Department of Applied Biology and Chemical Technology
College of Chemistry and Environmental Engineering
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