Deciphering intermediate excited states in spin-flip transition in carbonyl-nitrogen multi-resonance molecule
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Deciphering the intermediate states involved in the spin-flip transition in a multi-resonance (MR) molecule.
The transitions among different electronic states of the MR molecule are slowed by C2h symmetry.
The MR molecule exhibits narrow spectrum with an outstanding external quantum efficiency of up to 32.6%.
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ABSTRACT
Spin-flip process involving multiple excited states plays a key role for the function and application of many organic molecules. However, it remains extremely challenging to experimentally identify and investigate intermediate states in spin-flip transition due to its rapid inactivation via various electronic transitions. Herein, we report the deciphering of intermediate states involved in the spin-flip transition in a tailor-made carbonyl-nitrogen multi-resonance molecule (anti-DIQAO) designed with high symmetry. The transitions among different electronic states of anti-DIQAO are slowed by high molecular symmetry and distinguished using steady-state and transient spectroscopies. The second excited triplet (T2) state is identified as the intermediate state in the spin-flip transition, whose transition to higher energy levels and phosphorescence radiation are recorded. It is demonstrated that, in reverse intersystem crossing, intramolecular vibration drives the rate-dominant reverse internal conversion from the lowest excited triplet (T1) state to the T2 state, and thermal activation triggers transition from mixed T2 and T1 states to the lowest excited singlet (S1) state. Additionally, anti-DIQAO exhibits narrow-bandwidth electroluminescence with an outstanding external quantum efficiency of up to 32.6%. This research provides an effective molecular design to tune the populations of excited states, which is of high significance for exploring efficient luminescent materials. -
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REFERENCES
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Fu Y., Zhuang N., Liu H., et al. (2025). Deciphering intermediate excited states in spin-flip transition in carbonyl-nitrogen multi-resonance molecule. The Innovation Materials 3:100126. https://doi.org/10.59717/j.xinn-mater.2025.100126
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Fu Y., Zhuang N., Liu H., et al. (2025). Deciphering intermediate excited states in spin-flip transition in carbonyl-nitrogen multi-resonance molecule. The Innovation Materials 3:100126. https://doi.org/10.59717/j.xinn-mater.2025.100126
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Figure 1.
Two-dimensional vibrational space representation of potential energy surfaces when electronic states are
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Figure 2.
Photophysical properties of the molecules
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Figure 3.
Time-resolved emission spectra (TRES) of molecules
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Figure 4.
The analysis of exciton dynamics
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Figure 5.
Electroluminescence performance of the molecules in doped OLED
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